Alternator? Lights dont get brighter

[mrteach1973]

Hi

I had my alternator replaced with a RTX back on August and I think it is failing again.

Flickering lights, rough idle, Battery light is flashing on and off intermittedly

Does this all make sense?

Anyway been quoted for a LUCAS alternator as the DENSO ones are on back order.

Any one have any experience of these and whether they are worth the effort?

Many thanks

[Linas.P]

LUCAS is quite well known car parts company with long history, as such I would not really be worried about brand. In other hand - I was not aware LUCAS makes alternator for Lexus IS250, I would certainly double-check if that is correct part. 

[Herbie]

I don't know what an RTX alternator is or who makes them, but my first thought is to get it back and claim under warranty as it should last much longer than 6 or 7 months.

Lucas are the 'Grandaddy' of autoelectrical components and have been around for many decades. As long as it physically fits and has the right connections you won't need to worry about it for a long, long time.

[mrteach1973]

Hi

After some advice

I think my alternator is on the way out as when my lights are on full beam they flicker and go bright/dim/bright/dim.

I heard that if you whack everything on inside the car heaters, radio etc and then have yoru lights on and floor it, they should get brighter if the aternator is working well.

 

Does that sound right?

Anyway there was no difference in brightness and the full beam kept getting brighter than dimmer repeat....

Does this sound like the alternator is failing? Or does it point to another problem.

The car seems to rough idle as well 

[mrteach1973]

Should also say that the bumpy idle seems to sync with the lights getting bright and dim.

What does that mean?

 

[mrteach1973]

So when I turn my Lexus IS250 on and put the headlights to full beam, they get brighter than dimmer in time with my engine, as the engine idles.

They arent that bright either.

Do people think this is related to the wiring or maybe the alternator?

Im thinking more the alternator as it seems to happen in time with the jerky idle.

 

Any help would be fab.

Lexus IS250

[ColinBarber]

Possibly just your 12v Battery isn't charged or is not able to hold a full charge rather than assuming an alternative fault.

Do you have a volt meter you can measure the voltage of your Battery?

Do you have a Battery charger?

[m4rkw]

Could be a bad ground, try cleaning the Battery contacts. Be very careful disconnecting it.

[m4rkw]

https://www.digikey.com/en/blog/how-to-properly-clean-battery-contacts

I would start with that as it's pretty much free and if it doesn't work you haven't lost anything.

[ColinBarber]

@mrteach1973, in future please can you refrain from starting multiple threads on the same subject. You have created three which I've merged together.

[mrteach1973]

56 minutes ago, m4rkw said:

https://www.digikey.com/en/blog/how-to-properly-clean-battery-contacts

I would start with that as it's pretty much free and if it doesn't work you haven't lost anything.

Hi. The Battery connectors are really clean as is the Battery terminal...

[mrteach1973]

1 hour ago, ColinBarber said:

Possibly just your 12v battery isn't charged or is not able to hold a full charge rather than assuming an alternative fault.

Do you have a volt meter you can measure the voltage of your battery?

Do you have a battery charger?

Hi What am i looking for in regards to the numbers for the Battery when testing it?

Do I need to do it with engine off and on...with revs or not?

Many thanks for your help.

[mrteach1973]

Just now, mrteach1973 said:

Hi. The battery connectors are really clean as is the battery terminal...

Yeah all good.

[ColinBarber]

4 minutes ago, mrteach1973 said:

Hi What am i looking for in regards to the numbers for the battery when testing it?

Do I need to do it with engine off and on...with revs or not?

Many thanks for your help.

I would measure the voltage across the Battery with the engine turned off. You should see something around 12.4 to 12.8 volts. Then turn on the headlights for 30 seconds and see if the voltage drops under 12 volts. If it does I would charge the Battery before repeating the test. If after charging you see under 12v with the headlights on then your Battery is not in good shape.

If the Battery seems ok then start the engine, you should see the voltage read above 13 volts, and up to 14 volts if you rev the engine passed 2,200 rpm. Then turn on your headlights and rear window heater and make sure the voltage doesn't drop. That will test the alternator is working to a reasonable level.

[mrteach1973]

2 minutes ago, ColinBarber said:

I would measure the voltage across the battery with the engine turned off. You should see something around 12.4 to 12.8 volts. Then turn on the headlights for 30 seconds and see if the voltage drops under 12 volts. If it does I would charge the battery before repeating the test. If after charging you see under 12v with the headlights on then your battery is not in good shape.

If the battery seems ok then start the engine, you should see the voltage read above 13 volts, and up to 14 volts if you rev the engine passed 2,200 rpm. Then turn on your headlights and rear window heater and make sure the voltage doesn't drop. That will test the alternator is working to a reasonable level.

That sounds like great advice. Will borrow one tomorrow from my neighbout and give it a whirl. Do you know what the tester should be set too? As in current? 

[ColinBarber]

4 minutes ago, mrteach1973 said:

That sounds like great advice. Will borrow one tomorrow from my neighbout and give it a whirl. Do you know what the tester should be set too? As in current? 

You need it set to Volts, 20v scale if it isn't an auto-ranging meter. Definitely make sure you don't have it set to current (Amps) or have the lead plugged into the Amp socket.

Like this one:

[mrteach1973]

20 hours ago, ColinBarber said:

You need it set to Volts, 20v scale if it isn't an auto-ranging meter. Definitely make sure you don't have it set to current (Amps) or have the lead plugged into the Amp socket.

Like this one:

So did the tests as instructed.

Without engine on: 12.5  Then with lights on 12.04

With engine on: 14 Then revved 13.7. All the heaters lights etc 13.4...

Not sure what to do now...

 

[ColinBarber]

So there is definitely something wrong. I would expect to see the 14 v to be maintained when the engine is revved and when the lights turned on you may get a drop to 13.4 v for a fraction of a second but it should go straight back up to 14 v.

There is two possibilities. Either the cabling from the alternator to the Battery, or earth connections to Battery body and engine, has resistance in it due to a corroded or dirty connection or the alternator isn't performing as it should.

Not sure how easy it is to do but ideally you want to measure the voltage directly off the alternator and -ve terminal of the battery when the engine is running and lights/rear demister is on - if you see 14 v then the fault is with the cabling, if it drops to 13.4 v then the alternator cannot supply enough power (I assume due to a fault rather than it being the incorrect one for the vehicle).