RMK

To cut a long story short my alternator was acting up and making a slight humming sound when the engine was off which resulted in a drained battery. Installed the new alt and noticed a huming sound again. Ended up messing about with it and discovered that as manual fan switch that a garage rigged up causes the alternator to do this when the fan switch is turned off, but if it is turned on and the engine is off the humming stops.

Any ideas as to what is going on here?

Thanks for any help, as I'm stumped.

Vader

Any resolution? I'd start checking the diodes in the rectifier bridge, and review the wiring for the manual fan switch so it doesn't happen again.

RMK

Thanks for the reply. Still not got it solved yet. This is a brand new alternator that I swapped over before discovering that the fan being switched on stopps the humming noise.

Diodes in the rectifier bridge? I presume that is in the alternator? If so I now think the problem is in the wiring for the manual fan switch. What is the best way to wire a manual fan switch so I can compare it with what has been done to my car?

btw, just went out to the car about 30 mins ago and the battery was completley flat. I had not left the switch in the on position.

Thanks for the help.

RMK

Well from looking at wiring diagram the fan switch should tap into the ground wire for the relay. I'll have a look at the existing fan switch wiring and see where that leads me.