Rough idle

[Juris]

Hey guys, new member here.

My 09 IS250 has been rough on idle and I have read about carbon build up and also about other possible issues related with A/C and electrics. I am more inclined towards A/C and electrics because I read one of the post where the symptoms were exactly like mine ones. If I have A/C on and I stop in traffic lights engine drops down to 500rpm and feels like is about stall. My LED lights are flickering if A/C is on or I'm in reverse gear. Engine reacts even to seat adjustment which shouldn't be the case, right? So I thought it might be the Battery which I haven't changed since I bought the car and that's over 5 years ago now. So I went to Halfords the other day and they checked the Battery and said it seems to be fairly healthy one despite that I had some corrosion and buildup from acid around the terminals, which is a sign of needing a new Battery? But anyway I decided to clean the terminals and see if that changes anything. After reconnecting Battery I let the car run and switched on A/C and what seemed to be happening was that something was getting stuck/seized in A/C pulley and the rpms where jumping up and down. This had also happened some good while ago but it happened while I was driving and it stopped after that time so I didn't inspected any further at that time. But yeah, here I am with lots of questions but not many answers. What do you guys think? And should I take it to car electric for proper check?

[Vintagesixtysix]

I think your on the right track…

Looks like ac clutch is engaging and disengaging.

Did your ac work ok before this issue….

Is it fully gassed?

Does it work through the whole temp range?

Compressor issues are also not unknown.

[Linas.P]

Yes that sounds like stuck A/C compressor. I had that happen to me and basically A/C clutch tries to engage, nearly stalls the engine and disengages. There is next level to that - if the clutch also get's stuck, then it stalls the engine and you can't start it without removing the belt.

The fix - replace A/C compressor.

 

[Juris]

28 minutes ago, Vintagesixtysix said:

I think your on the right track…

Looks like ac clutch is engaging and disengaging.

Did your ac work ok before this issue….

Is it fully gassed?

Does it work through the whole temp range?

Compressor issues are also not unknown.

To be fair I haven't checked any of that as the A/C works just fine all the time, even when it was doing that, it was blowing air just fine. However just to be sure I will check again if it blows cold and hot air properly.

[Juris]

Just now, Linas.P said:

Yes that sounds like stuck A/C compressor. I had that happen to me and basically A/C clutch tries to engage, nearly stalls the engine and disengages. There is next level to that - if the clutch also get's stuck, then it stalls the engine and you can't start it without removing the belt.

The fix - replace A/C compressor.

Interesting. I assume it's not stuck entirely yet since one it's not doing this very often and two A/C seems to be working just fine. And do you think this is related with the other symptoms I described too?

[Linas.P]

How do you check if it is working when outside temperature is lower than lowest you can set on A/C?

In fact I once had this exact issue with Halfrauds - they re-gassed A/C and said it works fine, it was also November like now... I came back home, checked A/C and it does nothing. Came back and asked how did they test it, because it doesn't work... mechanic there came out with temp probe, stick it to the went, set the outside air, turn on the A/C and anounced confidently "look - it is blowing 7C"... then I pointed him out to the temperature read-out on the dash - it was 7C outside! Long story short - they refunded for A/C service.

Long story short - are you sure it is actually working, because if it is anything like my issue, then compressor does not turn at all. Also... I kind of doubt it works if A/C light is flashing, flashing light usually means there is problem with A/C system. Although you said "flickering", so maybe it is not the same thing. 

What voltage do you get from alternator? Should be around 14V.

[Juris]

10 minutes ago, Linas.P said:

How do you check if it is working when outside temperature is lower than lowest you can set on A/C?

In fact I once had this exact issue with Halfrauds - they re-gassed A/C and said it works fine, it was also November like now... I came back home, checked A/C and it does nothing. Came back and asked how did they test it, because it doesn't work... mechanic there came out with temp probe, stick it to the went, set the outside air, turn on the A/C and anounced confidently "look - it is blowing 7C"... then I pointed him out to the temperature read-out on the dash - it was 7C outside! Long story short - they refunded for A/C service.

Long story short - are you sure it is actually working, because if it is anything like my issue, then compressor does not turn at all. Also... I kind of doubt it works if A/C light is flashing, flashing light usually means there is problem with A/C system. Although you said "flickering", so maybe it is not the same thing. 

What voltage do you get from alternator? Should be around 14V.

That's a good point. But if the engine is hot shouldn't air be somewhat warm even if it's cold outside?

As for the lights flickering, it's not on the dash, it's my LED headlights. I don't have multimeter with me but I checked it some while ago and as far as I recall it was 13.6V

[Linas.P]

If you turn the heating on - then yes, otherwise it will be maybe couple of degrees warmer than outside air. So it is 4C outside and minimum temp on A/C is 16C... I am not really sure how do you know if A/C is working. The way to test it - you turn max heat and turn it on recirculation, it is nice if you have thermometer with you. So wait until it gets to say 24C, then turn A/C (still on recirculation) on and you should feel that air coming from vents is significantly colder. It think fully charged A/C blows ~13-14C on lowest temperature. But if temperature from vents is colder than that, then it is not coming from A/C.

13.6V is low, basically it is on the way out. I guess depends what is turned on in the car, but generally with engine running and just headlights you should be close to 14V. The alternator provides 14.4V, but obviously you needs some voltage to run the engine, so on perfectly working alternator you get like 14.1-14.2V. With loads of stuff turned on mine goes to maybe 13.95V, but generally stays just above 14V, which is healthy. 

13.6V... is not totally failed, but it will charge Battery very slow, to have any meaningful charge on the Battery you need at least ~13.2V from alternator (fully charged Battery is 12.9V).

When you say LED lights, do you have aftermarket headlights? I thought you meant A/C LED? 

 

[RONNIE W HODGEKINSON]

Juris..That is a strange Sequence of Faults and to Avoid Chasing your Tail Trying to determine the Problem/s I Think you Should let a Mechanic have a look at it Preferably one with lexus experience...At The moment your just going round in circles..Best of luck getting to the Bottom of This I Can Imagine your Frustration..!!

[Juris]

3 hours ago, Linas.P said:

If you turn the heating on - then yes, otherwise it will be maybe couple of degrees warmer than outside air. So it is 4C outside and minimum temp on A/C is 16C... I am not really sure how do you know if A/C is working. The way to test it - you turn max heat and turn it on recirculation, it is nice if you have thermometer with you. So wait until it gets to say 24C, then turn A/C (still on recirculation) on and you should feel that air coming from vents is significantly colder. It think fully charged A/C blows ~13-14C on lowest temperature. But if temperature from vents is colder than that, then it is not coming from A/C.

13.6V is low, basically it is on the way out. I guess depends what is turned on in the car, but generally with engine running and just headlights you should be close to 14V. The alternator provides 14.4V, but obviously you needs some voltage to run the engine, so on perfectly working alternator you get like 14.1-14.2V. With loads of stuff turned on mine goes to maybe 13.95V, but generally stays just above 14V, which is healthy. 

13.6V... is not totally failed, but it will charge battery very slow, to have any meaningful charge on the battery you need at least ~13.2V from alternator (fully charged battery is 12.9V).

When you say LED lights, do you have aftermarket headlights? I thought you meant A/C LED? 

 

So could the AC behave like this because of weak alternator too? Or it's all together AC compressor and alternator on it's way out? At this point maybe it's better to get it plugged in to diagnostics and that should perhaps clear things up?

Yeah to be more correct I have LED headlight bulbs not the whole headlights. 

[Juris]

1 hour ago, RONNIE W HODGEKINSON said:

Juris..That is a strange Sequence of Faults and to Avoid Chasing your Tail Trying to determine the Problem/s I Think you Should let a Mechanic have a look at it Preferably one with lexus experience...At The moment your just going round in circles..Best of luck getting to the Bottom of This I Can Imagine your Frustration..!!

Yeah, it's many variables and I might just do that, probably starting with diagnostics.

[Linas.P]

32 minutes ago, Juris said:

So could the AC behave like this because of weak alternator too? Or it's all together AC compressor and alternator on it's way out? At this point maybe it's better to get it plugged in to diagnostics and that should perhaps clear things up?

Yeah to be more correct I have LED headlight bulbs not the whole headlights. 

Hard to say... at first I thought your A/C LED is flashing and that would 100% be A/C problem, but rather it is headlight bulbs - so that is quite different. Also look at my video - it is not so much as "rough idle", but it is more of engine literally nearly stalling, and then revving-up again.

Your LED blinking could happen because of many reasons, they are aftermarket, so really could be anything... they may be short, they may be sensitive to bad alternator, they may be drawing too much voltage and that is why your readings are poor, also it could be short in Battery. So there are many things that could be wrong.

[Juris]

1 hour ago, Linas.P said:

Hard to say... at first I thought your A/C LED is flashing and that would 100% be A/C problem, but rather it is headlight bulbs - so that is quite different. Also look at my video - it is not so much as "rough idle", but it is more of engine literally nearly stalling, and then revving-up again.

Your LED blinking could happen because of many reasons, they are aftermarket, so really could be anything... they may be short, they may be sensitive to bad alternator, they may be drawing too much voltage and that is why your readings are poor, also it could be short in battery. So there are many things that could be wrong.

Yeah so just to clarify, as I understand your issue was persistent with A/C compressor being seized where's mine has happened few times over period of a year or so. This video was taken few days ago when I was cleaning terminals of Battery, so seems for whatever reason Battery being disconnected triggered it and rpms were doing exactly the same thing. Only difference is that in my case this is not persistent, it comes and goes once I a while. But then again apart from this issue there are other symptoms which I mentioned in my initial post and I will just have to check all the possible causes bit by bit. Either way, thank you very much, this has been very informative and I will keep you updated on how am I getting on with this.

 

Edit: I've added video from September when it happened, so essentially the same but A/C was still blowing air. 

[Vintagesixtysix]

I still think it’s pointing towards your AC compressor or pressure switch.

If it’s 22 degrees outside and you’ve just jumped in the car which the internal temp may well be warmer than 22 degrees

( possibly a lot warmer)

If your AC is set to Auto and say 20 degrees  it’s going to try and kick in pretty quickly on recirculating.

If it’s an intermittent fault….. which could be mechanical…… or your low on gas and appears when your putting significant load through the compressor ( it’s hot in the cabin etc)

As Linus has set out this can cause fluctuations in revs right through to a non start.

If your local daytime temps are lately anywhere between 10 -16 degrees there will be no load on the compressor if your cabin temp is say 20 degrees.

I have aftermarket LED bulbs and I’ve just completed my second Battery change during ownership.

When this Battery started to go bad I didn’t experience any headlamp flicker or other signs it just became difficult to start.

On the first Battery going bad it was like a disco in the cabin with lights fading in and out and rev dip…,then climb….then dip….. but not a bounce like yours.

Best of luck …,. Keep us informed …. These are always tricky.

Phil

 

[Spark plug]

This happened to my car. every time the AC came on she stalled. So I removed the AC fuse and she runs fine. I don't really need AC where I live rarely gets warm and if it does I open the windows lol... 

 

 

 

 

 

 

[Linas.P]

6 hours ago, Vintagesixtysix said:

I still think it’s pointing towards your AC compressor or pressure switch.

If it’s 22 degrees outside and you’ve just jumped in the car which the internal temp may well be warmer than 22 degrees

( possibly a lot warmer)

If your AC is set to Auto and say 20 degrees  it’s going to try and kick in pretty quickly on recirculating.

If it’s an intermittent fault….. which could be mechanical…… or your low on gas and appears when your putting significant load through the compressor ( it’s hot in the cabin etc)

As Linus has set out this can cause fluctuations in revs right through to a non start.

If your local daytime temps are lately anywhere between 10 -16 degrees there will be no load on the compressor if your cabin temp is say 20 degrees.

I have aftermarket LED bulbs and I’ve just completed my second battery change during ownership.

When this battery started to go bad I didn’t experience any headlamp flicker or other signs it just became difficult to start.

On the first battery going bad it was like a disco in the cabin with lights fading in and out and rev dip…,then climb….then dip….. but not a bounce like yours.

Best of luck …,. Keep us informed …. These are always tricky.

Phil

 

There is logic behind that -A/C compressor is running off the same belt as alternator, so if A/C compressor is binding, then alternator is also not turning as it suppose to turn and thus not charging as it suppose to charge.

By that logic - if A/C is turned-off, then we should see better than 13.6V on alternator. 

[Juris]

On 11/3/2024 at 3:00 PM, Linas.P said:

There is logic behind that -A/C compressor is running off the same belt as alternator, so if A/C compressor is binding, then alternator is also not turning as it suppose to turn and thus not charging as it suppose to charge.

By that logic - if A/C is turned-off, then we should see better than 13.6V on alternator. 

Hey Linas. 

Something else I've noticed today. I was away to park, put in reverse gear but my woman was getting out the car and as you open the door interior lights come on and what I noticed  is that they were flickering the same way as my LED headlight bulbs do and on top of that when I turned my steering left and right rpms dropped by 300. Since it's electric steering and AC wasn't on makes me wonder if this is all down to alternator and if so could AC act that way because of alternator going bad too? And also could that affect the steering itself by feeling heavy-ish? 

[Linas.P]

It may be the case that you have 2 issues... one related to A/C and one related to alternator, they could also be linked.

But first thing first... you need to measure what your alternator is doing again. 13.6V in my opinion is 50/50% - like it is not good, but if the car still drives and Battery charges, then it is fine, I would not be throwing it to the bin right away. Theoretical minimum with every single option turned on to the max is 12.8V, but realistically you want little bit extra. However if you have issues related to electrical side and you also confident alternator is only doing 13.6V, without anything but engine running, then maybe under load it drops below 12.8V (and 12.8V is a hard limit any thing below that runs on Battery directly and if say your alternator fluctuates between 13V and 12.6V, then this may cause all sorts of issues, flickering etc. and it would also destroy Battery quickly). So you need to confirm first what alternator is actually outputting. If it still does 13.6V when EVERYTHING is running, then I would say your issue is not an alternator, if however it drops below like 13.2V, then I would be replacing it. Even if it is not the issue you after, 13.2V is jut not good enough and such alternator is basically not charging you Battery sufficiently. 

So to start with, check that Battery is fully charged- anything above 12.6V is good (note - this is with everything off and ignition in "off position" doors closed etc., ideally you need to measure just the Battery itself, but it is pain to disconnect it on Lexus, so let's say 12.5V), if below 12.6V then start the engine and run it for 10 minute maybe, should be plenty to charge the Battery. Now - if after running the engine for 10 minutes Battery still does not show more than 12.6V, then either Battery is bad or alternator is bad. What Battery do you have? I had loads of issues with halfrauds and their Yuasa batteries (well Yuasa is not their brand, they have even shaitier line themselves, but they are the ones that sell Yuasa in UK). Some people actually recommend them, but I had nothing but trouble with them, they fail in all sorts of unexpected ways... and I have two failed Yuasa batteries that after charging measures completely fine and would pass any test. But one would not start the engine even once, and other would be dead after 3 attempts. They also mess up everything else in the way... and some of your symptoms could also be just Battery on it's way out. So that halfrauds tested it and said it was good - I would not put much weight into it. 

Assuming you pass previous step - start the engine and make sure everything is off, no headlights, no heated seats, no A/C, no radio... good alternator should be around 14V, again 14.2 is perfect, but if it is 13.9V still good. Then go and turn on things one by one and check if voltage is dropping - heated seats (in particular they draw a lot of current), headlights with high beam, music, A/C etc. check voltage again - if it drops below like 13.2V then you car is effectively running from the Battery. Voltage should be dropping slightly, but on my car even with everything running to the max I am still easily getting like 13.7V. 

So, yeah - first thing you need to check is that your alternator is actually alternating... if it does, then we can move to next issue on the list, but if it doesn't then it will cause all sorts of issues, or if A/C makes it to not run right, then again you can isolate A/C as a problem. In terms of probability I would say alternator failing is more likely than A/C compressor failing, although in my experience A/C compressor failed, but alternator was good past 200k miles (but usually is other way around).

Yes - steering being electric, can be affected by electrical issues. I never had bad alternator, but at one point I had bad Battery (original Panasonic) and PS would go from light, to hard basically at random. So in that case it was Battery fault.

Now - would A/C cause symptom because of bad Alternator... hard to say. In theory I can see how that could happen, but I have never seen it my self. So basically... let's speculate your alternator is just barely generating enough pixies when engine is idling... say it makes 13.4V at 900RPM, when you turn A/C RPM drops to 800 (AC compressor is like 3 HP, start-up may require maybe even 5HP)... that 100RPM different may be enough to go from barely sufficient 13.4V to something like 12.6V and as for short period car switches to run from Battery... you get heavy steering etc. Then when you driving maybe the car is at 1200RPM anyway and then you have no issue anymore. In theory that is possible.

[Juris]

10 hours ago, Linas.P said:

It may be the case that you have 2 issues... one related to A/C and one related to alternator, they could also be linked.

But first thing first... you need to measure what your alternator is doing again. 13.6V in my opinion is 50/50% - like it is not good, but if the car still drives and battery charges, then it is fine, I would not be throwing it to the bin right away. Theoretical minimum with every single option turned on to the max is 12.8V, but realistically you want little bit extra. However if you have issues related to electrical side and you also confident alternator is only doing 13.6V, without anything but engine running, then maybe under load it drops below 12.8V (and 12.8V is a hard limit any thing below that runs on battery directly and if say your alternator fluctuates between 13V and 12.6V, then this may cause all sorts of issues, flickering etc. and it would also destroy battery quickly). So you need to confirm first what alternator is actually outputting. If it still does 13.6V when EVERYTHING is running, then I would say your issue is not an alternator, if however it drops below like 13.2V, then I would be replacing it. Even if it is not the issue you after, 13.2V is jut not good enough and such alternator is basically not charging you battery sufficiently. 

So to start with, check that battery is fully charged- anything above 12.6V is good (note - this is with everything off and ignition in "off position" doors closed etc., ideally you need to measure just the battery itself, but it is pain to disconnect it on Lexus, so let's say 12.5V), if below 12.6V then start the engine and run it for 10 minute maybe, should be plenty to charge the battery. Now - if after running the engine for 10 minutes battery still does not show more than 12.6V, then either battery is bad or alternator is bad. What battery do you have? I had loads of issues with halfrauds and their Yuasa batteries (well Yuasa is not their brand, they have even shaitier line themselves, but they are the ones that sell Yuasa in UK). Some people actually recommend them, but I had nothing but trouble with them, they fail in all sorts of unexpected ways... and I have two failed Yuasa batteries that after charging measures completely fine and would pass any test. But one would not start the engine even once, and other would be dead after 3 attempts. They also mess up everything else in the way... and some of your symptoms could also be just battery on it's way out. So that halfrauds tested it and said it was good - I would not put much weight into it. 

Assuming you pass previous step - start the engine and make sure everything is off, no headlights, no heated seats, no A/C, no radio... good alternator should be around 14V, again 14.2 is perfect, but if it is 13.9V still good. Then go and turn on things one by one and check if voltage is dropping - heated seats (in particular they draw a lot of current), headlights with high beam, music, A/C etc. check voltage again - if it drops below like 13.2V then you car is effectively running from the battery. Voltage should be dropping slightly, but on my car even with everything running to the max I am still easily getting like 13.7V. 

So, yeah - first thing you need to check is that your alternator is actually alternating... if it does, then we can move to next issue on the list, but if it doesn't then it will cause all sorts of issues, or if A/C makes it to not run right, then again you can isolate A/C as a problem. In terms of probability I would say alternator failing is more likely than A/C compressor failing, although in my experience A/C compressor failed, but alternator was good past 200k miles (but usually is other way around).

Yes - steering being electric, can be affected by electrical issues. I never had bad alternator, but at one point I had bad battery (original Panasonic) and PS would go from light, to hard basically at random. So in that case it was battery fault.

Now - would A/C cause symptom because of bad Alternator... hard to say. In theory I can see how that could happen, but I have never seen it my self. So basically... let's speculate your alternator is just barely generating enough pixies when engine is idling... say it makes 13.4V at 900RPM, when you turn A/C RPM drops to 800 (AC compressor is like 3 HP, start-up may require maybe even 5HP)... that 100RPM different may be enough to go from barely sufficient 13.4V to something like 12.6V and as for short period car switches to run from battery... you get heavy steering etc. Then when you driving maybe the car is at 1200RPM anyway and then you have no issue anymore. In theory that is possible.

That's lots of good information, I will buy a multimeter and let you know how it goes.

Also, it's Toyota Battery, it's been there ever since o bought the car which soon will be 6 years and god knows how long before that. But as I mentioned before, there was some corrosion and build up from acid and I had to clean terminal.

Thanks again.

[Juris]

11 hours ago, Linas.P said:

It may be the case that you have 2 issues... one related to A/C and one related to alternator, they could also be linked.

But first thing first... you need to measure what your alternator is doing again. 13.6V in my opinion is 50/50% - like it is not good, but if the car still drives and battery charges, then it is fine, I would not be throwing it to the bin right away. Theoretical minimum with every single option turned on to the max is 12.8V, but realistically you want little bit extra. However if you have issues related to electrical side and you also confident alternator is only doing 13.6V, without anything but engine running, then maybe under load it drops below 12.8V (and 12.8V is a hard limit any thing below that runs on battery directly and if say your alternator fluctuates between 13V and 12.6V, then this may cause all sorts of issues, flickering etc. and it would also destroy battery quickly). So you need to confirm first what alternator is actually outputting. If it still does 13.6V when EVERYTHING is running, then I would say your issue is not an alternator, if however it drops below like 13.2V, then I would be replacing it. Even if it is not the issue you after, 13.2V is jut not good enough and such alternator is basically not charging you battery sufficiently. 

So to start with, check that battery is fully charged- anything above 12.6V is good (note - this is with everything off and ignition in "off position" doors closed etc., ideally you need to measure just the battery itself, but it is pain to disconnect it on Lexus, so let's say 12.5V), if below 12.6V then start the engine and run it for 10 minute maybe, should be plenty to charge the battery. Now - if after running the engine for 10 minutes battery still does not show more than 12.6V, then either battery is bad or alternator is bad. What battery do you have? I had loads of issues with halfrauds and their Yuasa batteries (well Yuasa is not their brand, they have even shaitier line themselves, but they are the ones that sell Yuasa in UK). Some people actually recommend them, but I had nothing but trouble with them, they fail in all sorts of unexpected ways... and I have two failed Yuasa batteries that after charging measures completely fine and would pass any test. But one would not start the engine even once, and other would be dead after 3 attempts. They also mess up everything else in the way... and some of your symptoms could also be just battery on it's way out. So that halfrauds tested it and said it was good - I would not put much weight into it. 

Assuming you pass previous step - start the engine and make sure everything is off, no headlights, no heated seats, no A/C, no radio... good alternator should be around 14V, again 14.2 is perfect, but if it is 13.9V still good. Then go and turn on things one by one and check if voltage is dropping - heated seats (in particular they draw a lot of current), headlights with high beam, music, A/C etc. check voltage again - if it drops below like 13.2V then you car is effectively running from the battery. Voltage should be dropping slightly, but on my car even with everything running to the max I am still easily getting like 13.7V. 

So, yeah - first thing you need to check is that your alternator is actually alternating... if it does, then we can move to next issue on the list, but if it doesn't then it will cause all sorts of issues, or if A/C makes it to not run right, then again you can isolate A/C as a problem. In terms of probability I would say alternator failing is more likely than A/C compressor failing, although in my experience A/C compressor failed, but alternator was good past 200k miles (but usually is other way around).

Yes - steering being electric, can be affected by electrical issues. I never had bad alternator, but at one point I had bad battery (original Panasonic) and PS would go from light, to hard basically at random. So in that case it was battery fault.

Now - would A/C cause symptom because of bad Alternator... hard to say. In theory I can see how that could happen, but I have never seen it my self. So basically... let's speculate your alternator is just barely generating enough pixies when engine is idling... say it makes 13.4V at 900RPM, when you turn A/C RPM drops to 800 (AC compressor is like 3 HP, start-up may require maybe even 5HP)... that 100RPM different may be enough to go from barely sufficient 13.4V to something like 12.6V and as for short period car switches to run from battery... you get heavy steering etc. Then when you driving maybe the car is at 1200RPM anyway and then you have no issue anymore. In theory that is possible.

So, I've done the tests and readings actually seem very good although I did them 10 minutes after driving so not sure how much that can affect them.

First test: with everything off and ignition off it was reading just under 12.5V. After running car for 10 minutes and everything off again it was over 12.6V. 

Second test: Car running with nothing else on it was nearly 14.20V. As I started switching on things one by one it was gradually dropping I think the lovest was 13.9V but once I had everything on (both heated seats, main and high beams, A/C on full blast, radio on) it was reading almost 14.10V 

So I am happy with that for now but then again I'm not sure how much is that to do with car being run shortly before, therefore I will do another test after car has been sitting for longer and let you know how it goes.

[Linas.P]

2 hours ago, Juris said:

So, I've done the tests and readings actually seem very good although I did them 10 minutes after driving so not sure how much that can affect them.

First test: with everything off and ignition off it was reading just under 12.5V. After running car for 10 minutes and everything off again it was over 12.6V. 

Second test: Car running with nothing else on it was nearly 14.20V. As I started switching on things one by one it was gradually dropping I think the lovest was 13.9V but once I had everything on (both heated seats, main and high beams, A/C on full blast, radio on) it was reading almost 14.10V 

So I am happy with that for now but then again I'm not sure how much is that to do with car being run shortly before, therefore I will do another test after car has been sitting for longer and let you know how it goes.

No - that sounds perfectly fine to me. No need to do another test. Alternator works fine. 

"Toyota" Battery I assume Panasonic? They usually have 8 years lifespan, so perhaps it is time to replace it, but again from what you are saying your Battery seems to be fine. Mine when I started having issues with randomly heavy PS already was giving me trouble, like car struggling to start just after 3 days being parked etc. Again lead-acid batteries are sometimes funky, you can charge them they show 12.6V and they pass tests, but then they cause intermittent problems. In your case I can't tell, replacing Battery that seems to which is fine would be waste.

So perhaps you looking at intermittent problem with A/C compressor or compressor clutch, compressor clutch relay. As you can imagine diagnosing intermittent problems is the most difficult thing.