Synergie Battery Light On at Low Revs??

Post by **AirCooledHeaven** » 27 Jul 2006, 18:11

I have a Synergie HDi, just recently the battery warning light has started coming on at anything below 1500 rpm. Above this engine speed everything is fine. The car starts instantly without problems and there are no signs of the battery being low, even though the battery is over 5 years old.

I'm assuming this is a charging problem but is there anyway to diagnose the problem using a digital multimeter? I don't want to start pulling the alternator off if it's a battery problem, nor do I want to fit a new battery and have it sh*gged by a duff alternator.

Cheers

Mark

JohnD · Post by **JohnD** » 27 Jul 2006, 18:45

Have you checked the tension of the belt? It may be too loose.

Post by **AirCooledHeaven** » 27 Jul 2006, 19:08

Ok well I checked the alternator belt and it doesn't appear to be loose, also with the engine running I can see the alternator rotating.

I checked with a voltmeter across the battery and I just had 12.3v at tickover with the warning light on. When I increased the revs the voltage went up to 13.8v and the warning light went out.

But here's the odd thing, after running the engine for a couple of minutes, the voltmeter dropped back to 12.3v and stayed there, even when increasing revs. But the warning light still went out at 1500rpm. When the warning light goes out I can hear a relay click inside the glovebox.

One other thing if it's relevent, when the warning light comes on the aircon panel goes blank, when the warning light goes out the aircon panel is back to normal.

I checked the terminals on the battery and alternator and they are clean and tight.

Any ideas?

THanks

Mark

3eme_attaque · Post by **3eme_attaque** » 27 Jul 2006, 21:24

i was always lead to believe if you weren't getting above 14v with engine running then your alternator is shot (and youve ruled out dodgy wiring). i would assume that your aircon dropping out is due to there not being enough voltage to power it, if your alternator properly goes then the electrical systems drop out one by one... assume the glovebox relay may be related to this...

Post by **Peter.N.** » 27 Jul 2006, 21:31

I would concur. The 'on charge' voltage should be 14 volts +or- a little bit, even at tickover, if it isnt the alternator is faulty. Do check the belt tension though, because even if you can see the alternator rotating, it might not be running at full speed.