18 replies to this topic

[JCmini]

998 1991 mini auto.

 

Just started to get this issue while driving my battery light come on and stays on. Then some time goes off. 

 

I fitted a volt meter just to see whats happening.

 

During motorway the light is off and volts read 13.7

When stationary at lights it reads 12.0

 

When i'm driving and the light stays on the it reads 11.5v

 

So with this in mind likely dead battery or alternator?

 

Thanks 

[cal844]

Change the alternator and also check the engine earth is clean

[JCmini]

Well I went to look at the alternator to check voltage. On idle at the alternator it was showing 12.2. I checked at the battery and it was 12.2. blipping the throttle raised the voltage to around 13.8. 

So the alternator seems to work. Its just sometimes when driving the red light comes on and it stops charging. 

 

Interestingly my voltage meter was showing 11.9.  The voltmeter is wired into position 2 (top right of fuse to work with ignition). I checked with my multi meter at the fuse and it was indeed 11.9. 

[Tornado99]

Check battery volts with it disconnected from car. Fully charged should be around 12.5 volts. If reading low Try putting it on a charger overnight to see if it improves. Also check if battery is the type that needs distilled water top up of cells. These will have removable caps on the cells and usually have a vent/spill over into tube connected near top and leading hopefully outside car body.

Edited by Tornado99, 15 November 2020 - 09:19 PM.

[richmondclassicsnorthwales]

Have a read on this article - it should help

 

 

https://www.goauto.c...essive voltage.

[JCmini]

Thanks. for that link. 

[JCmini]

Well i got a new battery and things improved a little. I do occasionally get the red light coming on while driving and I can see the voltage start to drop. Then couple minutes later the red light goes off and the voltage goes back up again.

Does this mean the alternator is on its way out?

[cal844]

Possibly, test it

[Quinlan minor]

I know it's an obvious question but what condition is the alternator belt in?

The voltages listed above are on the low side but, if you're using a dashboard voltmeter, I'd be concerned about the accuracy.

A proper digital AVO meter would be better or you could try one of these:

http://www.sparkbrig...age-monitor.php

 

[Tornado99]

Bad connections, ground points etc can also explain what you are seeing.

[JCmini]

Hi.

The belt seems in good condition.Its nice and tight so no issue with slippage. 

I took the battery earth out and cleaned it so that should be fine.  I did the same with the one from engine block to the back of the stabilizer(left of the engine) Is there any others to check. 

 

On a side note my voltage meter is connected to ignition which in general shows less for some reason compare to if I wired it to permanent live.  So eg when its showing 12.v the battery is actually about 12.6v. 

 

Today I went to drive it and the light stayed on while stationary. I blipped the engine and the light dimmed and then came back on. 

Edited by JCmini, 18 November 2020 - 06:58 PM.

[Tornado99]

Poor connections can occur anywhere between your warning light and the battery. You state there is a volt drop from ign to meter vs meter direct to battery, so your ign switch, or any of the connections that get power to it (fuse box connections for example) could be poor. 

[JCmini]

Ok thanks. 

 

Well it had now developed. When i go to start the car the light comes on. Despite revving the engine the light stays on. It does dim ever so slightly but goes back to being bright red when the revs drop. 

 

I have ordered a new alternator so will see if that sorts it out. 

[Tornado99]

Ok thanks. 

 

Well it had now developed. When i go to start the car the light comes on. Despite revving the engine the light stays on. It does dim ever so slightly but goes back to being bright red when the revs drop. 

 

I have ordered a new alternator so will see if that sorts it out. 

Seems like an expensive way to troubleshoot. 

 

Have you placed a voltmeter right at the alt terminals to determine if its output is in fact low? If it is putting out decent volts at idle (should be 13.5-14.2 normally....which gives sufficient for battery charging to occur), then your problem lies elsewhere. 

[JCmini]

Yeah I put my multimeter at the alternator. It was showing about 12.6 at idle.