Alternator issue - odd one

Post by **_h_____** » Mon Aug 02, 2004 10:03 pm

Guys,

This one is annoying me. The car is a 1957 2 door with a 1275 A+ engine with an alternator. Been running fine, but I have found on long journeys, the charging light will come on when idling(say at traffic lights).

With the car warm, if I start it at home and dont touch the accelerator then the warning light comes on and stays on. However, once I have tapped the accelerator, the light goes out and even after a long time idling doesnt come on again. These symptons are completely repeatable. It is as though on start up the alternator does not quite function properly.

On first start up (with no throttle and ignition light on), the battery voltage reads 12.20V, after tapping throttle, voltage reads 12.45V Again fully repeatable. So there is some difference.

I have tightened the fan belt, clean wires no change. The idle speed does not seem to change, although I have measured it (just be sound and vibration). Havent yet stripped the alternator to clean the brushes and contacts.

Anyone got any ideas? It never used to do this, and it is very annoying.

thanks

H

Post by **rayofleamington** » Mon Aug 02, 2004 10:16 pm

that sounds like normal alternator at startup. You have to give some revs for the alternator to energise itself, after which it should give a charge continuously.
(One thing that sounds odd is that it only reads 12.45 at the battery - normally it would be above 13)

As for the charging light coming on during a journey... sounds not great.

Post by **salty_monk** » Tue Aug 03, 2004 11:40 am

Sounds like the alternator might be on it's way out to me if all connections are good....

Post by **_h_____** » Tue Aug 03, 2004 8:47 pm

Ray sorry should have added values are tick over, I get nearer 14V when reving.

Didnt know alternators need to energise!

Also the light comes during journeys only at idle. Have checked all the wirng

still pursuing this one.

Post by **Willie** » Tue Aug 03, 2004 8:52 pm

It doesn't appear to be sick from what you say. (is your tickover
a bit on the slow side)?

Post by **Cam** » Tue Aug 03, 2004 9:12 pm

If your tickover is slow (as Willie says) then that could be the cause. If not then the regulator pack on the back of the alternator might be on the way out. I have had these fail loads of times and give symptoms similar to what you describe until finally the ignition light stays on regardless of engine revs. You can change the regulator pack (involves messing in the back of the alternator) if you can locate a replacement, or just get a service exchange alternator.

Post by **rayofleamington** » Tue Aug 03, 2004 9:25 pm

I get nearer 14V when reving.

when you are revving it should go to a stable voltage and not wander - if it drifts up and down a bit, the regulator could be faulty

Post by **Cam** » Tue Aug 03, 2004 9:26 pm

It's supposed to be (ideally) 13.8 volts when revving so 14 sounds OK. If it gets near 15 then something is wrong. Staying at 14 is fine.

Post by **_h_____** » Fri Aug 06, 2004 9:47 pm

Problem is getting worse, so will change the regulator pack (if I can find a replacement) and try that. Otherwise I will have to get a new alternator

Post by **_h_____** » Mon Aug 09, 2004 8:53 pm

Stuck a new alternator on in the end, was the easiest solution. Fixed straight away. Thanks for the help. And for my next problem see the mechanical section!!!!