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Electrical Problems

mxp01

Platinum Level Sponsor
I recently replaced the generator in my SIV. The take-out generator had "neg earth" stamped on the housing. The replacement generator (from VB) also had "neg earth" stamped on it as well. The car is positive earth.

Since the installation of the new generator the electrical system does not seem to be recharging. The ammeter only reads zero or in the negative. Previously, the ammeter would read positive (indicating a charging condition), but the needle would occassionally swing wildly from side to side, before settling in again to its charging position.

We did try repolarizing the generator, but it did not seem to make any difference. Can anyone provide some direction on this matter?

Thanks,
MXP
 

V_Mad

Donation Time
Check first that the ammeter is wired correctly by switching on a load (lights) and noting that the meter indicates discharge.

If your car is wired for neg earth, and worked OK before, then if the fitting and repolarisation of the generator (to neg earth) was successful, you should now have charge showing. It may not show a charge if the battery is fully charged although most systems do show a charge initially after starting regardless.

To polarise to neg earth, flash connect the field terminal to the battery (neg) supply, several times and make sure there is a spark indicating current is flowing.

Then connect up and run again. If there is still no charge I suspect either the generator is not wired correctly (field, earth and armature must be connected correctly) or it is a dud. You can test the generator with engine running by connecting the battery 12-14 volts (fused!) supply to the generator field, and then if your generator output (armature) is not well above 12 volts its a dud (or not polarised properly).

I am assuming your fan belt, regulator and wiring are still OK of course!

Good luck.
 

Tom H

Platinum Level Sponsor
You do not say why you replaced te generator. I assume it was because the system was not charging. You do not say how you determined the problem was te generator and not the regulator (controller). Could it be that the controller is bad?

Tom H
 
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