Alternator issues... AGAIN! less than 2 years old...

[MrTrendizzle]

Hey,  

So recently i've had an issue where my Battery light has been coming on but kept going away if the revs stayed up above 2k rpm. I did the normal tests with my multimeter and it showed the alternator charging the Battery at 14.5v and would drop back to 12.5v once the revs dropped to idle.  

I tested both the Battery terminals, alternator main post and even main post to body of alternator and it shows the alternator outputting 14.5v and only dropping once the revs dropped back to idle. I did notice that the revs would drop to 500rpm just before the alternator started back up again, revs climb on there own to 1k rpm and output 14.5v as normal with no load and while i place a load it runs at 14.5v but the Battery drained still to 11.5v  

I've fully charged my Battery on the kitchen table and left it over night and the Battery shows 12.9v once charging stops and in the morning 12.6v. If i use the Battery and place a load like defroster, heaters, lights etc... the Battery can drain down to 11.4v so i assumed it was the Battery not fully charging and showing a false reading considering the alternator seems to be outputting 14.5v... Well anyway last night i pop over to Halfrauds and pick up a new Battery, fit it myself in the carpark and the moment i start the car i'm met with the red glow of a Battery light.  

Maybe the Battery was not fully charged and only enough to start the car so gave it a drive home where the Battery light stayed off while driving but the moment i stop and idle the Battery light comes back on. Last night i gave up and felt like crying as costs have gone up on everything so i'm struggling to keep up. Honestly i'm at a loss as to what could be the problem. All the wires are tight and clean, the only one i havn't touched is the plug on the side of the alternator as i can't get my hand down the gap to unplug, clean and press back in. I'm not sure what that plug is for but it's the only part i've not touched yet. Can someone confirm if that plug could cause an issue please?  

Does anyone else have some insight in to what else i possibly could do before shelling out for a new alternator? I checked my email history and the Alternator is a genuine reconditioned Denso that's 1 year, 10 months and 2 weeks old.

[ColinBarber]

It sounds like the alternator isn't outputting enough at low speed and as a result has killed your old Battery. Not sure on the plug you are referring to on the alternator, will see if I can find some info.

[MrTrendizzle]

42 minutes ago, ColinBarber said:

It sounds like the alternator isn't outputting enough at low speed and as a result has killed your old battery. Not sure on the plug you are referring to on the alternator, will see if I can find some info.

The plug is the two/four wire plug that plugs in to the side of the alternator located near the main + post. (Plug for the voltage regulator it seems)  

Should an alternator always output 14.5v no matter the rpm? or does the alternator cut off once the Battery is fully charged while in use which explains why the alternator shows an output of 12.5v at idle and when the Battery light is on while the Battery tends to fall below 11.5v and the engine idles rough until you give it a little rev which then registers 14.5v output and the Battery slowly increases it's voltage?

[Spock66]

Maybe the problem is your idle speed is too low, should be about 750 I believe, if your idle speed is only 500 that could explain the Battery warning light coming on.

[Mr Vlad]

Eh up MrT. Sorry to learn about your car issues. 

As stated above 500rpm is too low and no matter what car that'll not be good for it.

I can't remember how to alter the idle revs but it certainly looks like it needs doing.

As for the recon alternator you bought. Personally I'd have gone for a genuine one. If I remember correctly the one I had to get was around £360 or there abouts. Don't know how much you paid for your recon but I bet it was near that.

Regards buying a new Battery. One should Always put it on charge with a smart charger before installing it in ones car. Especially if bought from Halfords. 

[MrTrendizzle]

1 hour ago, Spock66 said:

Maybe the problem is your idle speed is too low, should be about 750 I believe, if your idle speed is only 500 that could explain the battery warning light coming on.

Sorry i should clarify. The idle is 750rpm with the Battery light on, the revs drop to 500rpm and raises as the Battery light goes off for a moment almost like when you turn on the AC you notice the rpm drop slightly.

I've just done the school run and like this morning i've not had the Battery light come on and the idle holds strong at around 750+rpm which is a good sign i hope but still makes me scratch my head a little and worry about potentially only patching the issue with a newer stronger Battery. Will take the car on a long run to Bristol tomorrow with a spare in the boot. Luckily i have RAC roadside+recovery.

16 minutes ago, Mr Vlad said:

Eh up MrT. Sorry to learn about your car issues. 

As stated above 500rpm is too low and no matter what car that'll not be good for it.

I can't remember how to alter the idle revs but it certainly looks like it needs doing.

As for the recon alternator you bought. Personally I'd have gone for a genuine one. If I remember correctly the one I had to get was around £360 or there abouts. Don't know how much you paid for your recon but I bet it was near that.

Regards buying a new battery. One should Always put it on charge with a smart charger before installing it in ones car. Especially if bought from Halfords. 

The 500rpm is only when the Battery starts to charge again almost like the alternator kicking in and the engine dropping the revs a little. It does raise back up and settle at 750rpm but the Battery light comes back on and so the cycle repeats.

Both this morning and just now i've done the school run with zero Battery light so i'm guessing maybe my old Battery was dying and showing a false reading and the new Battery wasn't fully charged when i swapped it over. I'll have to get a smart charger, currently have a lipo charger with Pb setting so will have to invest in one.  

I'm off on a long run to Bristol tomorrow so hopefully any issues are fixed, but if the alternator does let go and is the issue i have the spare Battery in the boot which has enough charge to get the car started and move a few miles before i call out the RAC to recover me home.  

I think i paid around £130 for my alternator, i checked LexusDirect and they quoted £950... It's currently on sale with 20% off 😬 I've found a genuine brand new Denso alternator online for £180+20 postage so if all else fails i'll have to get that. Just sucks as i'm starting to struggle a little and every penny was to be saved for our first ever family trip to France in May which is looking a bit close for comfort if anything else goes wrong. This year i;ve already had to replace the fridge, washer, hoover, Battery and now possible alternator. Stupid sods law!

[Mr Vlad]

What? Lexus Direct are charging £950 for an alternator? That's effin Outrageous. 

I paid a little over £800 for supply and fit at Lexus Stockport. 

Something very very wrong with LD charging that.

[Spark plug]

1 hour ago, MrTrendizzle said:

Sorry i should clarify. The idle is 750rpm with the battery light on, the revs drop to 500rpm and raises as the battery light goes off for a moment almost like when you turn on the AC you notice the rpm drop slightly.

I've just done the school run and like this morning i've not had the battery light come on and the idle holds strong at around 750+rpm which is a good sign i hope but still makes me scratch my head a little and worry about potentially only patching the issue with a newer stronger battery. Will take the car on a long run to Bristol tomorrow with a spare in the boot. Luckily i have RAC roadside+recovery.

The 500rpm is only when the battery starts to charge again almost like the alternator kicking in and the engine dropping the revs a little. It does raise back up and settle at 750rpm but the battery light comes back on and so the cycle repeats.

Both this morning and just now i've done the school run with zero battery light so i'm guessing maybe my old battery was dying and showing a false reading and the new battery wasn't fully charged when i swapped it over. I'll have to get a smart charger, currently have a lipo charger with Pb setting so will have to invest in one.  

I'm off on a long run to Bristol tomorrow so hopefully any issues are fixed, but if the alternator does let go and is the issue i have the spare battery in the boot which has enough charge to get the car started and move a few miles before i call out the RAC to recover me home.  

I think i paid around £130 for my alternator, i checked LexusDirect and they quoted £950... It's currently on sale with 20% off 😬 I've found a genuine brand new Denso alternator online for £180+20 postage so if all else fails i'll have to get that. Just sucks as i'm starting to struggle a little and every penny was to be saved for our first ever family trip to France in May which is looking a bit close for comfort if anything else goes wrong. This year i;ve already had to replace the fridge, washer, hoover, battery and now possible alternator. Stupid sods law!

Brand new Denso £ 180???  Don't think so. Online fake Denso I wouldn't trust anything online. A good quality recon 1 cost me over £300 from Moterfactor.

[ColinBarber]

4 hours ago, MrTrendizzle said:

The 500rpm is only when the battery starts to charge again almost like the alternator kicking in and the engine dropping the revs a little. It does raise back up and settle at 750rpm but the battery light comes back on and so the cycle repeats.

The alternator has a clutch, it is enabled/disabled as required. I suspect when it is enabled there is extra load on the engine which pulls the rpm down and then the idle is adjusted to compensate. I don't think it should be that severe, and I wouldn't expect the Battery light to come on at all - Lexus state that would only happen if the clutch or alternator have issues.

Did you get a new clutch with your alternator, or did you swap that over?

[johnatg]

Have you checked all the earth points for engine and 12v Battery? Make sure all are clean and properly making contact with the body/engine/battery terminal.

[Mihanicos]

A full scan will give a very good idea what to look for.  Clean the throttle body butterfly to restore the engine rpm. Check and clean the mass air flow sensor.

Check for parasitic draw from the Battery, measure the milivot drop across the fuses.

 To pinpoint the cause of the fault you need the circuit diagrams of the car, preferably Alldata, precise, accurate very easy to use. Autodata is also very good.

Chris

[MrTrendizzle]

On 3/1/2024 at 8:36 PM, ColinBarber said:

The alternator has a clutch, it is enabled/disabled as required. I suspect when it is enabled there is extra load on the engine which pulls the rpm down and then the idle is adjusted to compensate. I don't think it should be that severe, and I wouldn't expect the battery light to come on at all - Lexus state that would only happen if the clutch or alternator have issues.

Did you get a new clutch with your alternator, or did you swap that over?

That would explain the rpm drop as the alternator comes on/off. Maybe a possible clutch pully bearing issue rather than an alternator issue as like i've said the alternator charges at the correct voltage and only drops to 12.5v just before the rpm drops which would be the clutch engaging.  

As the rpm drop significantly i would assume maybe the clutch/bearing could be worn out and causing the alternator/engine to struggle at idle. That would make perfect sense.
My long drive yesterday to Exeter (Location changed at last minute) i had zero Battery light the entire journey until i hit Exeter and had to idle in traffic for a few minutes and then it was on/off all the time.
The alternator was a complete unit so i didn't need to swap the pully over. I'll have to look around for a new unit unless a clutch pully is cheap and easy to change compared to the full unit.

EDIT: Just did some research and i think i have the wrong idea of how the clutch pully works on the alternator so swapping that might not be the fix. I'm just going to look at pulling the alternator out and replacing it if a good clean and quick slip test on the pully dosn't fix the issue. Found a video posted by a different member on how to test the pully. https://www.youtube.com/watch?v=fyosuYbPxr4

 

19 hours ago, johnatg said:

Have you checked all the earth points for engine and 12v battery? Make sure all are clean and properly making contact with the body/engine/battery terminal.

I've checked all connections except the voltage regulator plug as i'm unable to get my fat hands down the very small gap to unplug and clean.

[MrTrendizzle]

On 3/1/2024 at 4:14 PM, Mr Vlad said:

What? Lexus Direct are charging £950 for an alternator? That's effin Outrageous. 

I paid a little over £800 for supply and fit at Lexus Stockport. 

Something very very wrong with LD charging that.

Seriously i'm not joking... This has got to be a "We don't want to sell/fit this part" price, or the alternator comes with a lifetime warranty.

[Spark plug]

2 hours ago, MrTrendizzle said:

Seriously i'm not joking... This has got to be a "We don't want to sell/fit this part" price, or the alternator comes with a lifetime warranty.

I fitted a recon which cost just over £300 well over a year ago and have had no problems so far...

2 hours ago, MrTrendizzle said:

Seriously i'm not joking... This has got to be a "We don't want to sell/fit this part" price, or the alternator comes with a lifetime warranty.

On 3/1/2024 at 3:56 PM, MrTrendizzle said:

Sorry i should clarify. The idle is 750rpm with the battery light on, the revs drop to 500rpm and raises as the battery light goes off for a moment almost like when you turn on the AC you notice the rpm drop slightly.

I've just done the school run and like this morning i've not had the battery light come on and the idle holds strong at around 750+rpm which is a good sign i hope but still makes me scratch my head a little and worry about potentially only patching the issue with a newer stronger battery. Will take the car on a long run to Bristol tomorrow with a spare in the boot. Luckily i have RAC roadside+recovery.

The 500rpm is only when the battery starts to charge again almost like the alternator kicking in and the engine dropping the revs a little. It does raise back up and settle at 750rpm but the battery light comes back on and so the cycle repeats.

Both this morning and just now i've done the school run with zero battery light so i'm guessing maybe my old battery was dying and showing a false reading and the new battery wasn't fully charged when i swapped it over. I'll have to get a smart charger, currently have a lipo charger with Pb setting so will have to invest in one.  

I'm off on a long run to Bristol tomorrow so hopefully any issues are fixed, but if the alternator does let go and is the issue i have the spare battery in the boot which has enough charge to get the car started and move a few miles before i call out the RAC to recover me home.  

I think i paid around £130 for my alternator, i checked LexusDirect and they quoted £950... It's currently on sale with 20% off 😬 I've found a genuine brand new Denso alternator online for £180+20 postage so if all else fails i'll have to get that. Just sucks as i'm starting to struggle a little and every penny was to be saved for our first ever family trip to France in May which is looking a bit close for comfort if anything else goes wrong. This year i;ve already had to replace the fridge, washer, hoover, battery and now possible alternator. Stupid sods law!

Brand new Denso £ 180???  Don't think so. Online fake Denso I wouldn't trust anything online. A good quality recon 1 cost me over £300 from Moterfactor.