Alternator charging problem

Post by **Stubee** » Thu May 08, 2008 9:35 pm

Hello, my car seems to have developed a problem with charging the battery, the red ign warning light stays lit after engine start. I thought it was a duff alt so fitted a new one but it's the same. I'm getting the excitation voltage to the small terminal through the ign switch/red light. However I onlty have one large terminal on the alt output and this disappears into the main loom. I get continuity from the spade terminal to the L/H fuse in the fuse box. The bottom being a brown wire, the top pink. Should I then get continuity from here to the solenoid? Another odd thing is I connected a volt meter, +ve to the spare output terminal on the alt and -ve to earth. The voltage was way off the scale, is this right? Off to continue some more fiddling. How easy is to convert back to a dynamo!!?

Post by **polo2k** » Fri May 09, 2008 12:18 am

Sounds like the regulator is having issues. Do a search on here because i cant remember how to test it, I know its covered in all the books.

Post by **Alec** » Fri May 09, 2008 7:09 am

Hello Stubee,

do you have 12 volts at the alternator main terminal with the engine switched off? This will tell you if the alternator is correctly connected. As both alternators have the same problem it does sound as though it is not connected correctly? If the alternator doesn't sense the battery voltage it will over generate.

Alec

Post by **Stubee** » Fri May 09, 2008 12:57 pm

do you have 12 volts at the alternator main terminal with the engine switched off?

Yes there is 12v on the sense line with the engine off but igniton on.

What I did confirm is that there is no continuity from the start solenoid brown +ve wire to the outpput terminal on the alt. I only get continuity to the fusebox.
I will refit the old alt just to check the output as I didn't do this before removal as perhaps I now have two faults. The wiring problem and now a u/s on fit alt? Is it feasable to run a good wire from the alt output to the +ve terminal on the solenoid? Does it have to go through the loom?
Thanks for your help, these wiggly amp problems I find frustrating!

Post by **Alec** » Fri May 09, 2008 1:27 pm

Hello Stubee,

you should have 12 volts at the alternator main terminal at all times, not just with the ignition switched on. Yes you can run a cable outside of the loom, normal alternator connection is to the solenoid battery terminal but it could also connect to the battery as well. The solenoid being an easier connection point.

Alec

Post by **Stubee** » Fri May 09, 2008 10:09 pm

Have just tried slaving a wire direct from the alternator to the solenoid but still the same, but when I check the volts fro the +ve output to alternator casing it's way high

. Didn't get time to swap back to the old alternator so I will do that (could have buggered it if running with no load due to the wiring fault?) Might also look at getting another new one tomorrow. It should be simple really when I think about it, but....

Post by **alex_holden** » Sat May 10, 2008 9:15 am

Yes, I think running an alternator with no load tends to fry the regulator pack.

Post by **Stubee** » Sat May 10, 2008 11:06 am

Result

Fitted the old alternator in conjuction with the new wire direct to the solenoid and all is well. One thing with this alternator is it needs to be at quite fast idle to stay on line. I will probably still get another in case it is on its way out.
Thanks all.