Electrical Glitch

Hello folks, I am hoping that someone might be able to throw some light on a problem I had recently.
I have a 1996 2.5 lit non turbo Duetto.
We were off to the west (wet!) country recently and were on the M25 when the ignition warning light started to glow. (Not full on)
We stopped at the next services and I checked the aux drive belt and various connections under the bonnet to no affect.
I went to check the actual charge rate and realised I had left my multi meter at home.
While waiting for the recovery guy I amused myself by running a separate earth from the battery to the engine/chassis also with no effect.
After 2 hours the recovery guy arrived and put his meter across the battery and with me holding the revs at around 2000 he got a reading of 13volts with headlights and wipers on. So it was charging but not quite as much as it should.
I made the decision to carry on and kept an eye on the warning light feeling a little pleased that I had the old engine without any complicated electronics.
After a couple of days like this, the light went out of its own accord with everything back to normal.
Everything still seems fine but I wonder if anyone has any idea what may have caused the original problem.

Regards

It should be charging at about 14.7v. If its not then either faulty alternator or high resistance contact in the charge circuit. Whatever it is its obviously intermittent and will return at the wrong time!

I would go with Peter and probably lean towards the Alternator; fault possibly triggered by the rain? Worth whipping it off and getting it checked at an electrical auto repair shop. At least it would take it out of the equation.

Blossom wrote:
After 2 hours the recovery guy arrived and put his meter across the battery and with me holding the revs at around 2000 he got a reading of 13volts with headlights and wipers on. So it was charging but not quite as much as it should.

It could be something as simple as worn brushes / slip rings (probably brushes). As the outer brush gets worn down, it will begin to make intermittent contact and this could be the source of your problem.

As Jaytee says, whip it off and have it checked.

PS Is it the original alternator? If it is, then worn brushes start to sound more likely.

Thanks for the words of wisdom. I suspect it is the original alternator and with 102000 miles on the clock I guess it deserves an overhaul.

Regards.

Hi there Blossom, I agree with others and I think you are heading for an alternator change. I have known a battery light to come on in heavy rain. A combination of fan, wipers, lights, heated rear window and a slack belt. The type of belts used are known as Polyvee Belts. They rely on being tight to stop them slipping. You shouldn't be able to twist the belt as far as 90 degrees on its longest run.
As the recovery man did check, the charge rate should be 13.5-14 volts just above idle speed.The alternator has the brake vacuum  pump attached  to its rear end. Don't be tempted to go for the cheap option, alternator only. The seal between the  two units will leak, and more importantly this a part of the brake system and will be as worn as the alternator. You wont stop a Transit with a failed vacuum pump, I have seen the end results. 
Our 96 Duetto has had one alternator fitted in 95,000 miles, I have the bills to prove it. I fitted the new one. Not a bad job if you get the belt run correct.

Thanks Dave 418. I will check out the cost of a new combined unit.

Hi,
The brushgear/regulator on some alternators is only held in with a couple of screws, if its getatable you may be able to just replace that component,
Chris

Yes we did change brush packs on top end cars at the roadside. It had to be the Bosch alternators and difficult to remove at the road side. Saab 9000 were a good example, fitted down the back of the engine.
I would go for a full swap due to the age of the vehicle. What else is worn inside the alternator. I think you would have to remove the vacuum pump to get the brush pack out, potential leaks . Transit alternators were good for fix rates at the roadside, it saved a potential long recovery.

Hi,
Funilly enough I had to change the brushgear on my saab 900 some years ago, I remember the pain quite well,
Chris