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Strange Electrical Problem – Rectifier?


Nifty

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For a while now I’ve had a couple of minor problems with the electrics on my 1.4K SuperSport.

 

It started in June/July time when the Vectra immobiliser decided to cease functioning, fortunately with the engine mobilised. Therefore the light on the dashboard was constantly green. From this point on if the car was left for a fortnight unused the battery seemed to have been drained and the engine would need a jump start.

 

Having enquired about replacing the immobiliser I decided to chance my arm that it would stay as is (mobilised) and I would sort it with other jobs over the winter.

Since this first came to light I have had no other problems and the car has started without problems providing it has been used within the last week or so.

 

Until yesterday…….

 

I started the car up quite happily at 4.00pm and trundled over to Anglia Sevens for a minor alteration to the rear ARB. It started in Mark’s yard quite alright and I drove home. I then left it for about an hour to an hour and a half before jumping in to go to Cambridge. Turn key..click…nothing further.

Try this a few times, start swearing (already late) and climb out and proceed to jump start it from the truck. Fires up effortlessly and off I go.

 

Get to Cambridge (25 + miles) and stop to put fuel in. Go to start again and hey presto no power. Have to ask my passenger to push start. Leaving the garage I notice that the alternator/charging light is on, but dimly so.

 

When leaving the Cambridge meeting I once again have to get the car push started, alternator light still dimly lit when running at revs. Drive to Newmarket and drop off passenger and then head up A11 towards Thetford.

Hadn’t got far up the A11 when I notice that the headlights are somewhat dim and the alternator light is now much brighter – engine is running fine at 4,000 rpm +.

 

( The next bit happens in rapid sequence over the space of less than a minute )

 

Cruising along at between 80 and 90 I overtake a car and thinking lights are now bloody dim, hope I can get back home.

Decide to try mainbeam and flick switch, lights actually dim almost to nothing so rapidly switch back to dipped beam, lights pick up very slightly.

Suddenly no power whilst going up an incline at 80 mph. !!!!! 😳 😳 😳

Pump accelerator a few times but nothing.

Start pulling over towards grass verge to pull up when all of a sudden the engine comes back to life with a clunk (probably just the slack being taken up by engine suddenly relighting) and the headlights are back to full, normal, dipped beam brightness, though alternator/charge light very dimly lit still. *confused* *confused* *confused*

 

The car continues the rest of the 15 miles home in this state (with me driving as fast as I can to try to get the other side of Thetford before it decides to die again).

 

At Cambridge I was describing my lack of power to start the car after it had been sitting unused for a fortnight, then no starting power whatsoever today (yesterday) and the fact that the charge light was now dimly lit.

Someone suggested this mirrored his symptoms when the rectifier/diode pack on his alternator packed up and repair/replacing this would cure the problem.

 

However, in light of the cutting out incident and the just as sudden burst back to life and full brightness would this still be the possible cause of my woes????

I can’t fathom it out myself because if the rectifier was faulty I can’t see it repairing itself just like that???

 

It’s a mystery..can anyone help please??

 

Cheers,

 

Nifty.

 

 

 

🤔 🤔 *confused* *confused* *confused*

 

Edited by - Nifty on 17 Sep 2003 13:36:39

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Nifty

 

The dim alternator light means (as you probably know) that the alternator is not charging the battery. This could be a fault in the rectifier pack, but equally could be a battery fault. It would also account for the dim headlights.

 

The curious bit for me is the sudden loss of power and its equally sudden return. I suspect there is some problem with the battery connection to the alternator. This would explain the dim lights (battery not charging and being drained) and could explain the sudden loss of power. The ECU will only work down to a particular voltage..... about 6v. If the battery drops below this, the ECU will cut out and you will have no ignition or fuel metering - hence loss of power.

 

The reason I suspect a bad connection somewhere is the loss of power while on an incline. It could point to a bad connection moving under gravity up the hill which maybe slightly shorted out and dropped the ECU voltage below its critical limit. If so, it could also explain why it suddenly came on again as the connection moved when you slowed down.

 

Of course this is all an intelligent (imho) guess but it does fit the facts which a simple blown alternator and dead battery wouldn't.

 

Hope this is somewhat helpful.

 

Chris

 

2003 1.8K SV 140hp see it here

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Make sure your battery connections are clean and tight. If you can move/twist them take them off and clean them carefully with a wire brush. You also need to make sure that the alternator connections are secure. I think some cars are wired such that the positive supply to the car goes from the battery to the alternator and then to the rest of the car. So if either wire doesn't make a secure connection at the alternator you car may well exhibit strange electrical problems.
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  • 2 years later...

Blimey .. I was so much younger when I wrote this *tongue*

 

It was the alternator not functioning properly.

I had it revamped and everything worked fine after that .. though the power would drain out of the battery due to the faulty immobiliser which I then removed from the system.

 

Keep off the straight and narrow *tongue* 😬

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