ok, so the battery light on my '84 340 has been going on and off for awhile now.

basically, ive replaced the battery (needed doing anyway) the alernator twice, (first was faulty) and both times the alternators were fitted, the light has not come on for the first couple of drives. The belt tension is correct, and nothing is left on over night or shorts etc. does leaving the car for a few days without running it really discharge the battery that much? i m going to try and get hold of a new negative lead, as its a bit dirty. I honestly couldnt say what it would be. after a longish runnimg time, the battery light does go out, so theres got to be something discharging it.

any help would be awsome.

Cheers

Jon

If you're parking it up for more than a couple of days drop the negy lead off the battery.

yeah, its only a day at most between drives. i'll drive it till the battery light goes off, park it n leave it for a couple of days. see what happens.

A 300 should survive a few weeks or more on a well charged battery. Most cars these days last ok for that length of time and they have alarm systems on all the time.

Have you had any other symptoms other than the warning light, the battery light should go out immediately you start the engine, almost no matter what condition the battery. If it is not going out and you have replaced both there is a wiring problem somewhere, you are losing voltage or something. The voltage at the battery should be 13-14v with the engine running, if thats ok the problem could be with the battery light circuit itself.

Check the condition of the terminal that goes from the alternator back to the battery circuit. If the wire has corroded in the terminal it will give these symptoms. I had it on mine, wire had broke with only a few strands left, batt light was on very dim, but got me home. Replaced offending terminal and everything was perfect.
Adam

Ok, this problem has persisted for awhile now, just took to be norm, until yesterday, when it stayed on and the car nearly died. today i checked and cleaned all the terminals belonging to the battery/alternator circuit, to no avail. i ran the engine idling for awhile to see if the battery light would go out, and it didnt. There are no corroded terminals, everything is tight and not wobbly, and both battery and alternator are a couple of months old, if that.

I'm going to recharge the battery and get a volt metre on it to see if the alternators gone again, (surley not) after that i have no idea. Its really starting to grate now, as i love my volvo, and hate seeing it just as an enormous paper weight.

Lastly, could it possibly be a faulty thermostat by any chance?

I had similar symptoms and it was this.

340GLT wrote:Check the condition of the terminal that goes from the alternator back to the battery circuit. If the wire has corroded in the terminal it will give these symptoms. I had it on mine, wire had broke with only a few strands left, batt light was on very dim, but got me home. Replaced offending terminal and everything was perfect.
Adam

Perhaps if they are not frayed the wires have high resistance? I'd check this.

ugh, guess i'll have to. This'll mean loom taking apartness then?

Not necessarily, just test point to point with an ammeter. First two places I'd test are the battery and alternator Positive wires, then the grounds.

Speedy88 wrote:Not necessarily, just test point to point with an ammeter. First two places I'd test are the battery and alternator Positive wires, then the grounds.

Don't meant to be pedantic but I guess you probably mean Voltmeter or Multimeter. The OP need to measure volts to trace the fault as the battery is not charging, we already know there isn't enough current flowing in the charging circuit. Its volts that drives current and we need to know what is happening to the 14v from the alternator. Either it isn't generating it or it is dropping by the time it gets to the battery.

HOW DARE YOU... Yeah I just have a habbit of calling multimeter ammeters

Ha ha! i know you meant voltmetre the job for tomorrow this is. If i cant find a problem, would a new loom be an option? one from another 1.4 for example? im assuming i'd have to re time it and what have you?

Yeah bit extreme though, I'm sure with some patience you can find the one wire that's buggered and fix that rather than replacing the whole LOOM. You shouldn't have to re-time anything, they're only wires.



Or you could be lazy like me and chuck a battery jumper pack in the boot.

so i spent today going round every connection with a volt metre. everythings consistent, apart from the red small wire coming out the back of the alternator (showing 10 volts), next to the blue and red striped one. also, the battery + and another connection (can't remember exactly) count down from around that value. This has all lead me to believe the alternator has gone again. but 3 times in two months? i just can't beleive it!

If anyone has a spare alternator for a b14.4 1.4 they know is working and could sell me cheap thatd be wicked. i don't want to spend 100 + on a new one and find it wasnt the alternator.

Also, if any peeps have got any more ideas, shoot them my way.

What is the actual battery voltage with the engine running? I presume its low, ie 12.5v or something.

The small red wire goes to the warning light, and the blue/red one should be at battery voltage. There maybe a small ground wire for the field coils so make sure that is solid at both ends (or 0v between the alternator ground and battery ground, a small voltage will indicate a bad ground).

The warning light is part of the circuit and also needs a good connection, according to the circuit diagram there is also a resistor on the dash panel (gauges PCB) which is also needed. What the correct voltage for the small red wire is I don't know off hand, but I suspect this is where your problem maybe, assuming you havn't had 3 faulty alternators. A 360 dash has a white block ceramic 120ohm resistor in parallel with the light, I'd check around this for corrosion and correct resistance.