When I have my lights on in my 70 Maverick the right turn light in the dash comes on but the left one, the speedometer light, the heater control lights and the gear selector lights stay off. A couple of times they've come on but they always end up going off after a while. Does anyone know which wires go to them and what the problem might be?
I'm pretty sure you're turn signal switch is going bad. Have had the same thing happen before and that's what it took to fix it. Good luck with it.
Take 1 new turn bulb(1157) and change out 1 bulb at a time (check the sockets for corrosion when you change it) then retest. The park lamps use the same ground as the turn signals. If the ground is bad, or the bulb is shorted, or the socket is bad/corroded(likely the problem) one circuit will try and use the other for ground. When the lights are off there may be a ground path through the park lamps, letting the lights work. Lights on and the ground path is now a 12 volt source and 2 12 volt sources with no ground make no voltage. Turn switch is another place to look for corrosion but since the lights and the turn switch are electrically unrelated I would look at the bulbs/sockets first. Another area to look is at the plug at the back of the gauge cluster. Corrosion can build up and cause shorts between grounds, lights, and turn signal circuits. Also, the wires from the rear sockets through the trunk can be damaged by thing being thrown in and tossed around by driving. The wires from the front sockets to the body can be damaged from weather, wrecks, misc. debris, and chaffing on other parts. Lastly, the ground connections(where the grounds attach to the body and body to battery) can be corroded. Unfortunately these cars aren't getting any younger and any of the above can cause the problem.
there are two screws at the top of the gauge cluster, going upward into the top of the dash, usually Phillips drive. Then the cluster will tip out from the top. You will have to reach through the opening and disengage the speedometer cable, and also the main feed plug to the cluster in the center. Might take some finagling to get it out of there with the steering in place, but it can be done..You do not have to remove the dash.
Here's a tech article on the subject. When I did mine I had to release the speedo cable from the trans to get the cluster out enough to remove the cables from the back. http://mmb.maverick.to/showthread.php?t=39013