[gmc73]

Hi,, am installing new wires in the headlight switch, a 73, in my 73gmc truck. The problem is that the rear parking lights stay on. i have pic of the switch. Hope this helps. Thanks frankyjoe

[Cape Cod Bob]

The switch I used had the terminals marked. I would just take the wire off the switch that goes to the rear park light and put it on the same terminal that has the front parking lights on it.
That is. , if the front park lights stay on when the switch is pulled to the headlight position.

[Hoptup32]

I'm not exactly sure what is causing your problem, but the headlight switch requires two power sources, the headlights, dome light, dash lights and front parking lights receive power from terminal 928. The rear parking lights should receive fused battery power from terminal 959, which your diagram is showing handwritten as "Power feed for fuel pump switch"

[66GMC]

FREE Wiring diagram from Autozone

See Figure 7 for 73-76

[gmc73]

Originally Posted by Cape Cod Bob

The switch I used had the terminals marked. I would just take the wire off the switch that goes to the rear park light and put it on the same terminal that has the front parking lights on it.
That is. , if the front park lights stay on when the switch is pulled to the headlight position.

bob, the rear parking and rear turn signals stay on with headlite sw off. Thats my prob. i bought a new hdlte sw. and was tested at the auto store. It seems i am getting direct power thru these wires. tested by my trouble lite. There is no key in steering col. ign. Should the hdlte sw control this pwr to these wires?
thanks for any help gmc73

[Cape Cod Bob]

Disconnect the wires going to the rear lights at the switch and check them for a back feed. If they are clean , disconnect them at the taillights and check for grounds.and not grounded the problem is in the switch OR where the wires are connected to the switch. Follow 66gmc diagram or this link I posted. Just keep trouble shooting until located. Wires crossed up, harness misswired at factory, short circuit in harness etc.
http://www.goindesign.com/w4r/EZ2Wire-Manual.pdf

[gmc73]

bob, the scenerio now is 1 filament litall the timewith batt neg attached. no sw on. ? is the taller filament the turn signal iin the rear tail lights lamp. when trouble lite testing the rear r and l turn signals are lit all the time. at the steering col harness there is constant power thru the l and r turn signals wires. still truble lite testing rear ground wires.
hope this helps gmc73

[Cape Cod Bob]

Not sure which filament is which. The brighter is the brake/turn
The only circuit that should be HOT when the key is off is the brakecircuit and the headlight circuit.
I suggest pulling the turn signal flasher out, the hazard flasher out. These are separate circuits from the running lights. Then see what you got. There is something crossed up and believe me it will be simple. I have overlooked simple things and torn stuff apart only to find it. Then slap myself.
If the lights go out when you do this then look in those circuits for the feed and if it is wrong.

[EOD Guy]

I noticed on your dia that you're useing the org wire from the light switch to pwr the fuel pump. Unhook the fuel pump and see if that solves your problem. You might be getting a back feed from the fuel pump.

[gmc73]

Hi bob, there is short in the steering col harness the rear turn sig were on all the time. The taller filament is the stop light. Have to replace cancelling cam. thanks for your help. will let you know what happens.