Strange electrics!! SORTED cheers guys....

Post Thu Dec 29, 2005 11:49 am

Hi all found a weird problem with my 325 today. As it's cold and gloomy I got in my car and put my lights and heater on full blast. I noticed when sat stationary the heater slowed down as soon as gas is applied it works properly. The car starts with the turn of the key and always has, never had problems with the battery draining either

Any help on this one much appreciated

Post Thu Dec 29, 2005 12:06 pm

nice car mate....

old battery?

i found that the case when there too much draw/drain on the battery when i used to get stationary, with the stereo on loud, headlights and heater.....check the battery voltage - could be weak....as mine was - gave its a top up and a charge.....did fix the dimming problem

Post Thu Dec 29, 2005 1:21 pm

I would say at a guess it may be that your alternator isn't putting out enough amps on tickover and when you pick up the engine revs, the alternator speeds up providing more current output. Just a guess, but i hope this helps.

Post Thu Dec 29, 2005 1:38 pm

Battery is a brand new Bosch, I was thinking the alternator would most probably be the culprite. Any ideas how to check it?

Cheers guys

Post Thu Dec 29, 2005 1:40 pm

Firstly check the voltage across the battery. with the engine off it should be 12. with the engine on it should be between 13-14.5 ish

if both these are clear, its most probably a connection i assume. Turn the engine of locate the alternater and remove the plug. with the engine off check the voltage on the three terminals, they should all be 12v

if one of them doesnt have 12v, follow it and see if its corroded or disconnected from somewhere.

let us know, this is just basic checks!

Post Thu Dec 29, 2005 1:57 pm

i've got a feeling that an alternator can put out 13 - 14 volts, but the ampage may not be enough to run at low revs. The best way is to get an amp meter and check if the output is as the specified amount. On the other hand, it may just be a bit too much running all at once on a cold day. This time of year is always a real tester on any alternator, as most people drive to work with the heater, lights and radio on in the dark and then drive home exactly the same as it's dark when most people leave work. The battery really never gets topped right up and the alternator is under maximum strain.

Post Thu Dec 29, 2005 1:58 pm

Right engine off= 12.60v, engine running = 14.43v. I've removed the airbox to get at the alternator but can only see two seperate cables with rubber boots going to it. Do you mean these and if so how do they come off? don't want to break anything.

Cheers again

EDIT: didn't see your post toptints, which wire do I connect the meter to and I asume you mean with the engine running??

Post Thu Dec 29, 2005 2:05 pm

Not too sure about actually how to test it, as i have took mine to an auto electrician on my previous cars. sorry mate

Post Thu Dec 29, 2005 2:10 pm

toptints wrote:i've got a feeling that an alternator can put out 13 - 14 volts, but the ampage may not be enough to run at low revs. The best way is to get an amp meter and check if the output is as the specified amount. On the other hand, it may just be a bit too much running all at once on a cold day. This time of year is always a real tester on any alternator, as most people drive to work with the heater, lights and radio on in the dark and then drive home exactly the same as it's dark when most people leave work. The battery really never gets topped right up and the alternator is under maximum strain.

its between 13 and 14 when the engine is running, as technically the alternator is powering the car when the engine is on. try revving the engine to get this. 12vs hould read acros the battery with the engine off.

the two rubber plugs hsould just pull off a believe

tbh brianmooore is your best bet in this one, but the voltage readings you gave means the alternater is charging properly so its not that!

Post Thu Dec 29, 2005 2:12 pm

Don't think there's anything wrong. The altenator isn't going to push out it's full output at 750 RPM. I think it's just a case of using more power than the altenator is providing at tickover.

Post Thu Dec 29, 2005 2:22 pm

Brianmoooore wrote:Don't think there's anything wrong. The altenator isn't going to push out it's full output at 750 RPM. I think it's just a case of using more power than the altenator is providing at tickover.

I wont worry about it then, this is the first cold spell were I've had everything on at the same time.

Many thanks to everyone taking the time to advise, Happy New Year