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Here's the situation--when I turn the parking lights on, the green right turn indicator on the dash illuminates steady, and the right front side parking light does not come on. The front right side marker does come on. The right turn signal works--the dash right turn indicator light and the turn signal bulb flash, as normal. It's not the bulb as I've just installed a fresh one. The terminals in the bulb socket were slightly corroded but I've cleaned them up with a bit of emery cloth. My DMM quit working on me, just as I began to troubleshoot. I'll have a replacement here on Monday. Now when I resume the troubleshooting on Monday, how should I proceed. Suggestions/recommendations will be greatly appreciate.
I suggest replacing the bulb in the right front side marker lamp and also check the ground wires thoroughly on it and the turn signal. Seems to be bleeding over. Good luck.
Your turn signal switch may be shorted if you find no problems with the bulbs or sockets
When the turn signal switch shorts out on those old ones
They do weird stuff like hit the brake and the RF turn signal illuminates
The wrong bulb also causes similar malfunctions
Like a single bulb in a 2 wire socket
Make sure the bulb is grounded inside the socket. There should be a thin metal strip down in the socket that accomplishes the job. Usually after 40 some years that metal strip corrodes. A dab of bulb grease might help. As a last resort you might have to replace the socket itself. Most of the auto supply places have them and you're only messing with 3 wires. Easy peasy.
Chiming I’m on the ground comments. I recently had odd electrical behavior in the cab. Dome flicker. Radio reception suddenly would go out. Dim gage cluster. I checked my grounds. Battery to block ok. Block to firewall….. corroded. I pulled the ground and replaced with a 4 gauge cable. All issues resolved. This is unlikely your issue but it is a worthwhile first step.
This is a common issue on 70's Ford's when you turn on the park / head lights to have the dash turn signal light up and stay on till you turned on the turn signal and it works as it should.
If you turn on the park lights at night and check the lights on the side that the dash light is on you may find 1 light a little dimmer than the others.
IIRC it was always a front light (park / turn) not the rear because the way the turn signal / brake lights work.
The issue is a bad ground on the side the dash light light is on. One of the outside lights ground is back feeding thru the dash light making it come on.
Dont only look at the light bulb sockets but also the ground wires where they screw to the body. Remove the screw and sand the body & wire end and put back together. While at it check the ground from battery to body to make sure it is good also.
You have a body ground from battery dont you? Battery to motor, motor to frame, motor to body (firewall maybe).
Dave ----
X10 on Dave’s comments. Below is a pic of my firewall ground used by the cab electrical. I cleaned it up and that resolved most issues. It’s your easiest upstream consideration. Don’t spend time downstream until you validate grounds.
Firewall ground wire. 12”. 47 years old. In need of TLC.
This is a common issue on 70's Ford's when you turn on the park / head lights to have the dash turn signal light up and stay on till you turned on the turn signal and it works as it should.
If you turn on the park lights at night and check the lights on the side that the dash light is on you may find 1 light a little dimmer than the others.
IIRC it was always a front light (park / turn) not the rear because the way the turn signal / brake lights work.
The issue is a bad ground on the side the dash light light is on. One of the outside lights ground is back feeding thru the dash light making it come on.
Dont only look at the light bulb sockets but also the ground wires where they screw to the body. Remove the screw and sand the body & wire end and put back together. While at it check the ground from battery to body to make sure it is good also.
You have a body ground from battery dont you? Battery to motor, motor to frame, motor to body (firewall maybe).
Dave ----
Thanks, Dave; I think you have diagnosed my problem correctly. I have the OEM dual battery set up on my truck. I have all the grounds you mentioned, but I will definitely check all of them, and clean as necessary. Don't know what I'd do without the always helpful advice from my fellow forum members.
