E30 Zone

Hi all,
My e30 318i which is left on a maintenance charger has suddenly developed a fault in that the battery instrument light does not illuminate and the battery is not receiving a charge as I have put a multimeter across the battery when running,also I have checked the instrument panel light and that is not blown but does not illuminate when the ignition is switched on. I have also checked all of the fuses that I know of and these are OK. Can anyone help please.

I would replace the charge indicator bulb - how did you test it? it has a resistor in parallel with it so will show a multimeter reading even if its blown - at least whilst it is in cicuit.

Take the bulb out and stick 12v across it - does it light?

The feed from the bulb "excites" the alterntor - this makes it work - with a dead bulb it doesn't.

I'm sure Brian will add something here or correct my diagnosis

Welcome to the Zone!

Paul

Hi Paul thanks for your reply. I did take the bulb and socket out and put 12v through it and it did light. I have thought about swapping it with the oil light indicator bulb and see if this works which means stripping out the dash again.

Remove the smaller (blue) wire from the alternator, switch the ignition on, do NOT start the engine, and touch the terminal on the blue wire to a good body earth. The battery warning lamp should light. Touch the terminal on the bare alloy of the alternator. It should still light.
If it does for both, the alternator is the problem. If it lights on the body earth, but not the alternator alloy, check whether you have a rubber mounted alternator, and if so, check the condition of its earth lead.

mickes wrote: ↑

Thu Dec 19, 2019 5:08 pm

Hi Paul thanks for your reply. I did take the bulb and socket out and put 12v through it and it did light. I have thought about swapping it with the oil light indicator bulb and see if this works which means stripping out the dash again.

Welcome to the Zone mate and Brian is the one (and Paul.lol) for the electrics.
Pics of your car will be well received mate.

Mart.

Brian, I have done the checks that you said and the ignition lights in both cases so its looking like the alternator. Do you have an idea of what particular component has failed as I have thought of stripping and repairing it myself.
Thanks for your help.

You probably won't even have to remove the alternator from the car. Regulator pack is on the back end of it, held in place by two small cross head screws. Remove it, and check the condition of the carbon brushes.

I have removed the regulator and checked the brushes and there is plenty of 'meat' left on them and they are moving freely,have cleaned everything up and put it back but there still is no ignition light and is not charging.

Had my doubts that it was just worn brushes, since they normally fail by becoming slightly intermittent at first, then gradually getting worse as they wear. I thought maybe a brush had suddenly and completely broken up, although this only normally happens on devices with segmented commutators, such as a dynamo, rather than the smooth commutator of an alternator.
I'd still expect a new regulator pack to put things right though. Unusual for the electronics in it to fail, but not impossible.

Do you think it is worth buying a new regulator then Brian or biting the bullet and getting another alternator?

Assuming you have a Bosch alternator, Google the number on your reg. Should be 1197 311 ***.
Prices start at around £8 and fitting takes five minutes, so I'd definitely try that first.

Managed at last to get hold of a new Meyle regulator,could not get a Bosch, at last and this has sorted the problem so thank you Brian for your help. Glad that I found this forum.

The Meyle regulator is probably the one I would have gone for. Reputable brand, and a lot cheaper than a genuine Bosch one.
It's unusual for the regulator to fail, other than for worn out brushes, which are part of the pack. These are the cause of 99% of charge light problems, but there's another similar thread on the go at the moment, and that doesn't look like it's going to be worn brushes either!