strange problem

[amantedifiat]

Hi all,
Hopefully someone can help me with this electrical issue.
1980 spider. All electrical works fine but sometimes when I put the headlights on they will not work and alternator light
goes on. Switch to parking lights and they work okay. Wipers do the same thing. They will work and then I'll put them on and nothing and alternator light goes on. This is all why the car is running. Lights and wiper will work fine. Stop the car for fifteen minutes and bang no lights or wipers!!!
It comes and goes and is driving me nuts. No problem starting car. Cleaned all grounds, changed negative battery wire and cleaned bolt and surface it mounts too.
What have I missed!!!
Has anyone had this problem?
Any suggestions will be much appreciated.
Thanks

[vandor]

Intermittent ignition switch problem? Try wiggling the ignition switch wires when the lights don't work.

[amantedifiat]

I'll try that tomorrow. Thanks for the reply!!

[spider2081]

also
The alternator light should only come on when the alternator output voltage is less than the voltage on the wire to the alternator from the alternator/battery warning light. The light power gets to the ignition switch on the brown wire on terminal 30 of ignition switch. When the switch is in the "start & run" positions it is switched to the battery warning light and the headlights. The ignition switch has a blue/ black wire on the "int" terminal that goes to C31 the connector behind the switch. In the cars side of that connector there is a blue red and blue wire mating with the blue /black from the switch. The blue wire feeds the headlight switch and the blue red feeds the battery warning light. IF you don't find a connection problem as vandor suggested I would remove voltage regulator from the alternator and inspect the brushes.

[amantedifiat]

Thanks for the reply. I should also mention that this problem occurs when the car is not running???
Mark