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Electrical question.

2307 Views 66 Replies 12 Participants Last post by  Snulma1
I have an electrical problem I’m trying to wrap my head around.
Dissasembled my dash to replace my gauge cluster, redo the radio, repaint, and then replace my heater core and wiring.
Swapped out the gauge cluster, and tested the lights with them all working. Then plugged back in the wiper switch and seated cluster as well as screwed in.
Went to check the cluster one last time and they lit up but then went dark.
Thought that may be the battery was low, so pulled it out and placed on a charger for two hours. Placed back in and the lights lit up and the wipers worked but then everything clicked off again.
I’m assuming there’s a short somewhere but not sure where to start. Does anyone have any suggestions? 
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Sorry 68 convertible with 200 ci engine.
I forgot I also swapped out the starter solenoid too.
I’m far from an electrical expert but if you had a short I’d think it would blow a fuse and it would not have relit the 2nd time at all. Maybe a loose connection somewhere would be my first guess.
I was thinking that too but same as you, I'm no electrical expert
Does the 68 have the two resetting circuit breakers in the headlight switch like the 65/66? If so you probably have a short and it keeps tripping and resetting?
How would I know?
Also, something weird, walked away from the car to take care of other things came back up route one hour later and found the headlights on. However, the keys were out of the ignition, and the headlight switch was all the way in/off.
Any ideas?
Pinched wire behind the cluster?
I know I probably need to take the cluster back out, but it took so much effort to finally get it in. It breaks my heart to remove it again
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For the 7 cluster lights, check the 2.5A fuse.
The headlights don't need the key on, but they do need the knob out. Check that the knob shaft is engaged with the switch, but it sounds like a bad light switch, which could also cause a problem with the cluster lights.
I will check the fuse tomorrow, but it is a brand new headlight switch. I installed it three weeks ago.
is there anyway to check it?
If I may,
I had a similar problem after I installed my Dakota Digital cluster.
Mine turned out to be one of the main connectors on the firewall going to the engine bay. I thought it was all the way seated, but it was only partially seated.
Just a thought,
So you’re saying that it wasn’t seated all the way in the cluster?
If the instrument cluster lights DON'T work but the horn DOES work then it's NOT the headlight switch.
Hmmm. I’ll have to check that. Explain to me how that works?
What Woodchuck is saying is that they are both powered by the same circuit breaker inside the light switch. But there is still a switch that could also be defective in "On" or "Park" (circled in yellow).
View attachment 865340
So I pulled the cluster and made sure everything was seated and a good ground. So far everything is working.
But what’s weird is if I pull the light switch to the first stop, the dash lights and the marker/fog lights light up. But if I pull to the second stop, the dash goes off and the headlights come on.
Is that normal?
No. The instrument cluster lights should stay on in both "Park" and "Head" mode. Make sure you have the correct headlight switch as some are "pinned" differently. It sounds like the cluster lights are getting power from the "park" feed. Are the parking lamps on with the headlamps?
No they are not. And neither are the taillights.
Then I'd pull the headlight switch and test it with an Ohmmeter against the wiring diagram. If it appears correct then I'd check the "pinout" of the headlamp switch plug.
I’m sorry still sort of a newbie when it comes to electric. I have a multimeter (7 Function Digital Multimeter)
I can pull the headlight switch but not sure how to do the remaining.
Grab your multimeter, set to the 200 Ohms scale, put the RED test lead on the "B" (battery) terminal on the switch, move the switch through its positions and check the other pins with the BLACK lead as shown below.

View attachment 865402
Is there a specific reading I’m looking for?
As close to zero as possible.
Sorry, I didn’t follow the directions the first time.
Everything has continuity in the proper positions, except for D1 and D2, which have no continuity at all.
Sine "P" did not change it sounds like you have a "bum" switch. "P" should be near zero with the switch in the first pulled position. D2 should be near zero with the knob turned all the way CCW into the detent.
I went back and retested, realizing I didn’t follow the directions properly. Only D1 and D2 don’t have continuity I’m assuming that still means bum switch.
Sorry, Look for continuity between D1 and D2, with the knob turned all the way.
There’s only continuity between D1 and D2 if it hits the point where the courtesy lights should turn on
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There’s only continuity between D1 and D2 if it hits the point where the courtesy lights should turn on
I assume that means the switch is operating properly. So what would be my next step?
Exactly WHAT stops working properly when you have your issue? Just the instrument cluster illumination or more?
The marker lights and the cluster don’t work when the headlights are on.
When you say "marker" do you mean the front side marker lights or the front parking lights? The front parking lights do NOT work with the headlights, only in the "PARK" (1st) position. If the cluster lights work in the "PARK" position but shut off when you pull the switch to the "HEAD" position then either the switch is defective or the plug is wired improperly.
Sorry I meant the parking lights.
So since the cluster turns off when in the head position, and we tested the switch and it has the proper continuity it must be a wiring issue right? Any tips on figuring out where the issue lies?
Check that the BLU/RED wire is properly located in the headlight plug in the slot matching up with the "I" position. If it IS, examine the rheostat and its contacts that something isn't moving when the switch is pulled out all the way.
Rheostat makes good contact through CW and CCW rotation and into contact point. I looked at the Blu/Red wire and it’s seated properly with a clean contact point.
If I follow the discussion properly, you have an open in the wire somewhere in the highlighted area. Disconnect battery cable, with headlight switch on you should have continuity (almost 0) between A (or B) and R. Where are you located? depending on where you are I or someone I know may be able to help you. I'm in NC.
View attachment 865889
Just to make sure I understand, if I use ohmmeter on the wiring harness for the light switch and test between A(or B) and R I should have continuity?

I live in northern NJ. Anyone near and willing to help would be appreciated!
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