alternator problem ?

[sandro]

SmileWavmy 928 alternator problem is that it will not charged below 1000 rpm.
i have rebuild it complete but still the seem problem, have anyone have an idea what the problem can be ? thanks

[Danglerb]

Could be a problem with the exciter signal to the alternator. Does the charge warning light come on when the car is started?

BTW generally you need to tell us what model year and Euro or US car you have.

[surfdog4]

second danglerb comment...the light bulb for the alternator warning is part of the circuit..

[Alan in AZ]

Maybe the belt isn't tight enough - it will always slip more at idle - this is the worst case for loading so that it works at higher rpm is no indication. It needs to be really tight.

Alan

[sandro]

Originally Posted by Danglerb

Could be a problem with the exciter signal to the alternator. Does the charge warning light come on when the car is started?

BTW generally you need to tell us what model year and Euro or US car you have.

hay ,it is an 928 year 1982 and a us model

[sandro]

Originally Posted by Danglerb

Could be a problem with the exciter signal to the alternator. Does the charge warning light come on when the car is started?

BTW generally you need to tell us what model year and Euro or US car you have.

it is an 1982 and an us model.
the light does go on ! thanks

[sandro]

Originally Posted by Alan in AZ

Maybe the belt isn't tight enough - it will always slip more at idle - this is the worst case for loading so that it works at higher rpm is no indication. It needs to be really tight.

Alan

i think it is ok but i will check it again, thanks

[sandro]

Originally Posted by Danglerb

Could be a problem with the exciter signal to the alternator. Does the charge warning light come on when the car is started?

BTW generally you need to tell us what model year and Euro or US car you have.

yes it does go on !

[Danglerb]

Make sure the belt is not slipping.

Make sure the contacts are really clean and tight, not just on the alternator but both ends of the motor ground wires.

Pull the alternator and have it tested.

Not saying its the way to go, but I think I will put in one of the Delco CS130 alternators the first time one of mine hiccups. Before changing it though, its good to make sure the rest of the system is working.

[sandro]

Originally Posted by Danglerb

Could be a problem with the exciter signal to the alternator. Does the charge warning light come on when the car is started?

BTW generally you need to tell us what model year and Euro or US car you have.

hay , the model jear is 82 and an us car.
the light does go on .

[Alan in AZ]

Well the question is also - when does the light go on - when you turn the ignition on before start I presume its on - after starting does it go out immediately? does it come on again when the rpms are below 1000 rpm?

If it does - it seems highly likely you need the alternator rebuilt - possibly just new rotor brushes or a new regulator (usually both are replaced together).

Alan

[sandro]

Originally Posted by Danglerb

Could be a problem with the exciter signal to the alternator. Does the charge warning light come on when the car is started?

BTW generally you need to tell us what model year and Euro or US car you have.

it is an 1982 car and the light does go on, thanks. us model

[sandro]

Originally Posted by Alan in AZ

Well the question is also - when does the light go on - when you turn the ignition on before start I presume its on - after starting does it go out immediately? does it come on again when the rpms are below 1000 rpm?

If it does - it seems highly likely you need the alternator rebuilt - possibly just new rotor brushes or a new regulator (usually both are replaced together).

Alan

the light goes on when i turn on the ignition an goes oud when it start and stays oud. when it drops below 12 v the warning light on the middle consle and the oxs light on the dashboart goes on.

[785sp]

Alan, here's a further thought/question. I'm just about to put in a third alternator in a 78, after two rebuilts that lasted about 5 months each. I mentioned my experience to the guy I use to do the regular maintenance on my 'family' cars (being too lazy to change oil in my wife's car, of course), and his first thought was that I had a short somewhere that was killing my alternators (rather than being worthless rebuilts as your prior post suggested). Now, I'm not about to trust the word of an oil change and coolant flush guy, but could he be right? If I have a bad ground or some other short, could that actually burn out an alternator, rather than just impair its function?

[Randy V]

Hay, but does the light go on?

[Danglerb]

Shorts that kill alternators tend to make a show of sparks and smoke, since the alternator is also hooked directly to the battery. Trust me on this one, shorting anything directly connected to the battery on a 928 is an event.

What failed on the old alternators?

[785sp]

Originally Posted by Randy V

Hay, but does the light go on?

Both had the same symptoms: First, the alt dash-gauge started dipping to 10 or 11 at idle up to about 2,500 (the well-known 'exciter' malfunction). Then, the max voltage at the dash started showing a little bit under 12, even though the voltage across the battery terminals was still showing above 13. Then, the alt warning light started coming on and off seemingly at random. Then, the alt warning light came on and stayed on, plus the adjacent oil level warning light came on and stayed on (despite full oil levels). Finally, the alt dash-gauge sunk permanently to about 10 or 11, and then it was all over once the battery discharged about 100 miles later. This sequence has happed twice.

Incidentally, I have already cleaned the mail ground at the rear of the car, and I've already crimped new connectors at the alternator. One thing I haven't done is trace the alternator ground back up, as it appears to go up through the wire harness and then back to the block or engine mount area somewhere, but I may have mis-read the wiring there.

So, two bad rebuilt alternators, or some other problem? Could a bad alternator ground (once I find it) cause the alternator to burn out like this?

[Alan in AZ]

dangerlb is correct - any short that would affect your alternator would have killed a bunch of batteries first and you'd not be able to hold a charge even for a few hours -so its not that.

A damaged battery can cause an alternator to do wierd things and could eventually kill it - but usually damaged batteries die pretty quickly themselve necessitating replacement...?

The alternator is usually grounded by its case and the big bolt to the block - its very unlikely that is loose... yours may be different?

In any case if the alternator lost its ground connection you'd loose charging - but it would be unlikely to damage the alternator.

Go to a different place to get the alternators rebuilt always use a specialist auto electrics place - do not use a chain - they just swap parts...

Alan