Battery Light On, But Charging Fine...?

[Bovien 6]

Ok, I have found that good grounding will turn on the light as you say. I have also measured that I have 14.2v @ alternator with engine running and 14.1v @ battery.

This tells me that the alternator is working perfectly, but the signal to the spade connector is bad. I havent't been able to measure any noticeable voltage at the connector, as it is very hard to get proper connection from a multimeter to it. I will test that out tomorrow.

But assuming I can't get a proper voltage at the connecter, I'm guessing I have a fault in the alternator right? And it is probably easier to get a replacement from a breaker for 20£ than to take it off and attempt a renovation, right?

[jackherer 543]

0.1v is actually a potentially significant voltage drop, I'd check the thick wire from the battery to the alternator (via the starter) and the ground wire from the battery to the gearbox (including the battery terminals.) The connections to the alternator, starter and gearbox should all have toothed washers to ensure a good connection.

[Bovien 6]

Ok, been measuring more now,and I'm even more confused:

 

Whit the engine running I have 17.5v on the spade D+ terminal, 14.5v on the B+side of the alternator! same on the battery, so a difference of 3v to the spade plug.

When the engine is off, I have 1.5v on the spade and 12.5v on the battery side.

 

I don't get it. If I connect the spade to the charge B+ on the alternator, the light is off. Why do I have a higher voltage on the spade when charging and a very low voltage whit engine off? Do I just have a bad alternator?

[Weser 30]

Well going from what you have said above and asuming your readings are correct we can now see why you are getting you battery light on. You have like you said a potential difference of 3v going (backwards) across your battery light.

 

I must admit I have never looked at this circuitry on the car or in the haynes so am going from the above diagram.

 

The Battery light will be off when you connect it to the B+ side of the alternator as that is providing the same voltage as the ignition to the battery light so therefore no potential difference causing the light not to come on.

 

I am not sure whether you are supposed to have the 1.5V on the D+ terminal when the car is off. My guess is not but someone can clarify. To me it is pointing to the problem being to do with whatever provides the voltage on the D+ terminal on the alternator. is this the voltage regulator?

[jackherer 543]

I agree with the above, if your meter is accurate (a low battery can cause false readings) the voltage regulator in your alternator has failed. You run the risk of damaging some electrical components and the battery can boil over so you should fix it before you run the car any more.

[Bovien 6]

Sounds Rights to me, that it is a part of the alternator (guessing the voltage regulator is part of it) is at fault. However, the charging voltage to the battery seems very stable @ 14.2-14.4v. It is only the spade to the battery light that measures 17v. So I'm guessing that I'm safe regarding charging the battery and electrics. I've driven several hundred km since the error showed and apparently no issues.

However, I will get me an altinator, I just need to be sure that is the issue

[jackherer 543]

OK, if your battery is only seeing 14v it should be safe. The regulator is inside the alternator, I've replaced them separately on other cars but they don't seem to be widely available for Peugeots. I can't see anything else that could cause over voltage there, it has to be the regulator I think, the only place higher voltages are produced is the alternator and the regulator should stop them reaching anywhere else, including the battery light.

[Bovien 6]

Ok, we are on the same page then. Any idea of which engines the 1.9 shares alternator with? Here in dk, the breakers usually carry 1.0 and 1.3 and diesel, and they are not the same as far as I can figure..

[welshpug 1,622]

Diesel 205 alternators will fit, as will many of the earlier 306/405 possibly 406 etc,

[Bovien 6]

Thanks, I'll look for that

[Bovien 6]

Ok, swapped alternators with one that came from a 1.9 like mine. However, they are not the same. This "new" one has what looks like two D+ spade connectors and my own one only one spade connector.

 

I tried the least rusty one and that seemed to work fine. Then this morning, driving to work, the light came on again after 10 min...... So, now I just switched to the second spade and starting up the engine all looks well, but I can't get down there with a mulitmeter to measure voltage. Access is impossible. So can anyone shed light on what the two spade connectors are and if they are the same?