Flat Battery Part 2

[Richard Grove]

OK, now I am stuck again.

 

New alternator and battery fitted. When the engine is running I only get 12.6v accross the battery terminals i.e its not cahrging.

 

I have done a continuity check as follows :

 

Ignition switch on. Unplug the connector from the alternator and check for voltage between the 3 pins on the connector and a good earth.

 

The middle pin gives 12.6 volts, the other red wire gives 1.6 volts and the small pin (blue wire) reads 0.

 

I think the 0 on the blue wire means the warning light on the instrument panel has blown.

 

Should the 2 red wires both read 12 volts?

 

Any ideas where the problem might be ?

 

Thanks

 

Richard

[Mat-Moo]

I made a stupid mistake when I wired up my alternator, the huge wire going from it to the battery was a black wire, and I assumed (!) that it was negative. This gave me similar issues, and it wasn't until I realised that it was black sheathing over a red wire as to where my mistake was.

[Longboarder]

Don't run your alternator unplugged to measure voltages. It can blow it. There will be very little output if the blue wire from the warning lamp is not connected as this provides the field current to excite the rotating windings. Connect it all up, clean all electrical contacts and correctly tension the fan belt!!! Make sure the battery is fully charged, start and run at fast idle for 5 minutes and test voltage across the battery terminals again.

 

Nigel

[Richard Grove]

Don't, worry I was not trying to test the voltage with the engine running, just the ignition switched on.

 

Any way problem is now sorted. I can confirm that both red wires at the alternator plug should read 12 volts. After stripping back 12 inches of black insuating tape I fould that the wiring had been cut and simply twisted back together. A couple of years of corrosion on the wires meant a very dodgy connection.

 

Thanks for everyones help.

 

Richard