Engine running 12.5 volts = alternator not working?

[AlBundy]

As per subject, the battery performance was poor, running down a lot more regularly than it should, and last week didn't start at all.

Removed battery, charged, and it started immediately, so something is off.

When the van is running the battery reads 12.5 volts, and slowly creeps up, 12.51, 12.52 every 10 seconds or so.

My assumption is if it was all working properly the engine battery should read 13+ volts and hold it.

Does it make sense that there is an issue with the alternator, or could it be something else?

[Mocki]

The brush pack in your alternator needs changing i would say .
But first you need to perform a couple of simple tests ……...


Take a voltage reading at the alternator ( using the casing as neg )
If you have less than 14v between the alternator output and the casing , either the blue wire isnt connecting or the brush pack is faulty
If you have 14v on the first test Then take another another from the alternator pos using the van body as neg connection , if there is any difference between these two readings clean the earths , both the actual facings on the alternator to the bracket and the gear box nose earth strap , then take another voltage reading at the battery .
If you have a difference of more than 0.5v between those readings and the readings at the battery it’s connections or wire fault,
Clean earth faces and earth leads .
Thirty plus year old wires go high resistance , sapping your power with in the cables before they even get to the battery


https://brickwerks.co.uk/product/voltag ... use-14-5v/

[davidoft1]

Check the alternator belts tight , does it change if you go over 2500RPM

[AlBundy]

Update on the issue, or non issue (or not an issue worth fixing yet?).

Short journeys the voltage doesn't get up to a high enough value to charge the vehicle battery, but after a few minutes, it does. When I tested it at home, it was usually for a short period, so never really got high enough, in the garage the mechanic couldn't replicate it, so the problem seems to have sorted itself out.

What he did find was that there was a drain on the battery from the Sargent EC155 PCU, the stereo, and the immobiliser which was why the van wasn't starting regularly, it wasn't charging to sufficiently top up the battery, and the drain was causing it to discharge faster than expected.

[keynsham1]

I checked mine qt the alternator and at the battery (1.9DG). I get 13.8V at the alternator and around 13.2V at the battery. I have an aftermarket voltmeter on the dash but it always reads low which is why I checked! It rarely goes about 13V.

My batteries stay charged so I am happy!!