Bulb Holder Help!

The tubular portion of the sockets often get corrosion preventing a ground connection.

Might try and clean it up some.

 

I discovered the same problem a couple of days ago. I cleaned it some and put the old bulb back in, it worked temporarily but the next day it was not working again. I used some Deoxit and put a new bulb in, it worked for a day but now today it is not working again. As suggested, I am going to give it a through cleaning.

I have had similar problems on old (1969) BMWs before. They can be frustratingly difficult to permanently fix in my experience.

 

This is not a meaningful measurement when the bulb is removed and the current is zero -- if there is a high resistance somewhere in wiring/connections, this will still measure +12V, but, when you add a current load, the voltage will drop to zero -- i.e., you really need to make the voltage measurement when the bulb is plugged in (which, I know, is not so easy to do).

Some figures describing this are in this thread:
http://www.ferrarichat.com/forum/technical-q-sponsored-algar-ferrari/56353-308-cooling-thermo-switch-problems.html

 

perhaps you're using right side bulbs😀

 

'79 GTS. I've had the same problems with mine. I discovered that the ground connection on the bulb housing/holder is terrible. On mine, it is a braided bare wire squeezed between the bulb holder and the light housing, this does not make a good connection. I'm going back in again to rectify this. Will probably run a new ground and solder it to the bulb holder.