Headlight/Dimmer switch ohm test

[eltigrez]

Can anyone tell me how to ohm test my light switch and dimmer switch on a 69 Rallye Dash? When I turn on my headlights it blows the 20A tail light fuse. I have isolated the rear harness, unplugged cig lighter and ohm tested pink wire to headlight switch and cig lighter wire and they test good. Pulled the dash, all looks good. WonderIng if my switch or dimmer is bad.

 

[Pops1967GTX]

nm9stheham FABBO wrote this and I used it to troubleshoot.
You can test the switch out of the car per this info, and use it to know when/what should be connected.

B1 (Battery 1) should connect to H (Headlights) when the switch is pulled all the way out. There is an internal circuit breaker between these 2 contacts; those can fail open occasionally.

B2 (Battery 2) should connect to R (Rear? Red? the tailights anyway) and to P (front Parking lights) when the knob is pulled to either the 1st or second positions.

B2 also feeds the dimmer rheostat in the switch; the resistance from B2 to I (Instrument lights) will vary from maybe 15-20 ohms down to near 0 ohms as you rotate the knob.

D (Dome) should connect to the switch's metal case/body when the knob is turned all the way to where it 'clicks' to turn on the dome light


Repairing Headlight Switches And Horn Relays - Hot Rod Network

Make Your Gauges Like New Again! - Hot Rod Network

 

[oldbee]

Sounds like you have a dead short after headlight switch and if you unhooked rear harness at left kick panel then you know it's not in there rear.

 

[Pops1967GTX]

Check the factory wiring harass AT “welded splice” where wires branch off to the ignition switch, light switch, and the fuse box. You might find your problem there....

 

[oldbee]

You did say that "tail" fuse is blowing; that wire is purple and feeds 4-way flashed, stop light switch and up to hdlight switch with a lead going from there going to factory tach.

 

[oldbee]

But upon further looking, that purple wire is hot all the time. Does it blow fuse when in 'park' position, first detent?

 

[eltigrez]

Thanks for all the replies... Keep em coming The car is a 4 speed no park position. I'm blowing the 20A tail fuse. If I'm quick I can see the tail lights glow before the fuse blows. Yes, I disconnected the tail harness and it still does it. I dont get it, there are only 2 wires to the circuit. Taillights and lighter. When I put in a new fuse the lighter works. Splice possibly. Will a switch or dimmer do this? I checked the ohms on the dimmer and headlight switch. Dimmer seems to change resistance when you rotate the wheel. Light switch maybe a little.

 

[oldbee]

I meant the parking light position on hdlight switch. Unhook your tail harness behind the left kick panel, then everything rearward is out of the picture.

 

[eltigrez]

Yup, pulled the plug for the tail harness. Still blows

 

[eltigrez]

Sorry, I misunderstood. YES, blows fuse in when headlight switch is in park position.

 

[Shorthorse]

I could be way off on this but after looking at two different wiring diagrams (none designated as "rallye dash" if there is a difference) it appears looking backwards that the black wire from the tail lights is common at the light switch connector (B2 as Pops said) with another black wire that goes to the dash light dimmer switch. At the dash light dimmer switch connector, that black wire is spliced/common to a yellow tracer wire. The yellow tracer wire then goes to the front parking lights and the lights on warning buzzer.
It suggests to me that the front parking lights would also be inoperative and there's more circuit to look at. I'm not sure why the fuse says "tail lights".
Just guessing here.

http://www.mymopar.com/downloads/1969/69BelvedereGTXSatelliteRoadRunnerA.JPG
http://www.mymopar.com/downloads/1969/69BelvedereGTXSatelliteRoadRunnerB.JPG

http://www.mymopar.com/downloads/1969/69BelvedereGTXSatelliteRoadRunnerFull.pdf