Speedo quits when lights on!!??

warpspd · 03-04-2005, 09:59 AM

I have got a weird electrical problem. My car is a 76 euro carrera.

When I turn the parking lights on, key off, all guages light up
correctly.

Turning on parking lights, key on, all guages light up but
the speedo is dark.

Drive car during the day speedo works fine: odometer rolls over
and mph work just fine.

When I turn my lights on while driving neither the mph or the
odometer work nor the lights in the speedo. If I do this during the day I can be going along the the speedo read mph fine but if I mometarily turn lights on BAM the mph falls quikly to 0mph.

I cant figure this one out. Could it be something in the headlight switch or ignition switch?

jimbauman · 03-04-2005, 10:18 AM

I have the same problem, but at least I know why! Years ago, one of the connections on the back of the speedo came loose, and shorted out, causing the insulation on one of the wires going back into the wiring harness to melt. It's a real mess, and I never bothered to fix it, but the symptoms are the same - when the lights go on, the speedo goes dark and does not work. So, when I drive at night, I don't rack up miles on my car.... Oh well.. So basically it sounds like you have a short somewhere....

JB

warpspd · 03-04-2005, 11:15 AM

I figured it out just now. One of the piggy back connectors
on the speedo broke and left it without a ground. I guess it had just enough ground to glow dim until the key was on. I just happend to be testing out the ground and found the broken
connector. I grounded it to known good ground and the lights
on the speedo got really bright compared to no ground. I am going to buy a new connector and hopefully it will be good to go.
I just got through re wiring my headlights to individual relays. Next step is to get the trunk cleaned up and painted.