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The headlight switch needs a separate ground, do you have #7 installed?
The tail lamp fuse sends power to the instrument light fuse, are they both good?
If the instrument fuse blows only the dash lights will go out.
If the tail light fuse blows both the instrument lights and the tail lights will be out.
Also is the green wire at the headlight switch plugged in properly?
I read something today that later model C3 instrument lights went out if tail light bulbs were blown. Any truth to that?
The headlight switch needs a separate ground, do you have #7 installed?
The tail lamp fuse sends power to the instrument light fuse, are they both good?
If the instrument fuse blows only the dash lights will go out.
If the tail light fuse blows both the instrument lights and the tail lights will be out.
Also is the green wire at the headlight switch plugged in properly?
Fuses all replaced. Checked each w/multimeter and all have continuity. Green light wire plugged in correctly
The dash lights gets their power in a convoluted way-
Green wire comes from the tail light fuse to the headlight switch reheostat- back down to the 1/2 size "inst lps" fuse - changes to gray and then goes up to the dash lights.
If you have an OEM radio- that should light up too- it's on the same circuit.
You need to check for power at the fuses -
if you have power at tail lights but not the inst one- you have a bad connection in the fuse box- rehoestat- or connection at the headlight switch
If you have no power at the tail lamp fuse- probably need to pull the fusebox and check for corrosion behind it
I was set to do that last night but I think I may have found the culprit. I checked all the fuses ,except the little 5 amp fuse. I never though that it was for the lights. I was worried checking the one that said gauges. When I tested it, it was blown. I bought some on my way to work today and can't wait to get home to see if that fixes. it. I will feel so stupid if that fixes it. I will let you all know. If not I will check the harmonica.
Last edited by RobMc1963$; Feb 2, 2021 at 01:27 PM.
UPDATE: Replaced the 5 amp fuse and most of my lights cam on. Two on Speedo side and twin the Tach side did not. Took the m apart and redid to make sure connections were good. Still do not work. Pulled common ground apart and made sure all grounded and it was. Still did not work.
Here is the weirdness. When I hit brakes four dash lights come on. Two on Speedo side and two on tach side. No running or brake lights on rear. When I click turn signal several lights on dash light up poorly on Speedo cluster. Right turn signal several light up brightly.
I never did anything to any of this. All I did was cut grey bulb holders out and added a two wire LED bulb holders.
I had dim brake lights before.
Any guess?
The 'harmonica connection' is at the lower part of the column did you check for power there?
I figured out the majority of power issues but if you looked at my update seems may have purchased a possessed auto. Would a reversed harmonica”ncause these issues?
If you have somehow connected the harmonic connector wrong- you'd have way more issues than what you are seeing. But do check and see if it is plugged in correctly.
The front and rear turn signal lights are on a separate circuit when they come out of the steering column harmonica. The indicators in the dash are fed off the front lights
I'd disconnect the 12 pin harness for the rear (right above the fusebox- below) and see what happens.
You need to "divide and conquer"- to narrow down the issue.
Sounds like it might be a bad bulb - maybe a single filament in a dual filament holder - no ground on the front lights- who knows?
If the turn signal switch has been replaced the Harmonica Connector at the bottom of the steering column will not mate up Evenly with harness connector. Go to Willcox technical section and there is a guided that shows the correct pin placement for replacement Harmonica Connectors. The turn signal lights run through the turn signal switch/harmonica connector.
I read your statement about adding new bulb holders (for new LEDs) that have TWO Wires. The positive wire from the new bulb holder should connect to the GREY wire, and the other wire will should connect to Ground. The metal housing of the tac/speedo are the Common Ground for all the illumination bulbs.
UPDATE: Replaced the 5 amp fuse and most of my lights cam on. Two on Speedo side and twin the Tach side did not. Took the m apart and redid to make sure connections were good. Still do not work. Pulled common ground apart and made sure all grounded and it was. Still did not work.
Here is the weirdness. When I hit brakes four dash lights come on. Two on Speedo side and two on tach side. No running or brake lights on rear. When I click turn signal several lights on dash light up poorly on Speedo cluster. Right turn signal several light up brightly.
I never did anything to any of this. All I did was cut grey bulb holders out and added a two wire LED bulb holders.
I had dim brake lights before.
Any guess?
The first thing I would do is to check the ground wires and bulb connections for the tail lights
I also have a 73 coupe, my suggestion, get rid of all that burned,crusty, rusty, harness and put in a new wire harness. I got a universal 21 circuit harness cost me 80$ it comes with all instructions every cable is color coded, upgrades the old glass tube system and it can be done in a weekend. Cheers!
I also have a 73 coupe, my suggestion, get rid of all that burned,crusty, rusty, harness and put in a new wire harness. I got a universal 21 circuit harness cost me 80$ it comes with all instructions every cable is color coded, upgrades the old glass tube system and it can be done in a weekend. Cheers!
That would be great. Where did you get it, if I may ask?
I read your statement about adding new bulb holders (for new LEDs) that have TWO Wires. The positive wire from the new bulb holder should connect to the GREY wire, and the other wire will should connect to Ground. The metal housing of the tac/speedo are the Common Ground for all the illumination bulbs.
I did check that out from another helper. They are correctly hooked up. Most of the dash lights are working except for 2 on each side. One is the light blue for the turn signal and the other is a grey wire dash light.
That would be great. Where did you get it, if I may ask?
Good old Ebay of course. However do a search and order items by price, you will see 4 different ones, the one I got looked better quality than the rest and upon delivery it didn't disappoint at all, However they all seem to be listed for gm and Ford, I'll attach the link to the one I got it comes with warranty the fuse base is good quality and everything is clearly listed, there is one that has nothing listed on the fuse base another one you can tell is cheap because you can barely see what's written on the fuse base and last, has one round relay and this one has 2. Also good thing about this is you can upgrade all your lights, radio, add electric fan, pump etc with no fear of any short circuit and you will know where everything is hook up, I also got a 73 factory wiring harness diagram and tried to follow it as best as possible. Some modifications need to be done but nothing you cant if you have some basic electrical knowledge. Cheers!
Love to hear a little bit more about the modifications that you had to do. I have average skills with adding ends. My soldering is week. Also had did you not get wires mixed up? does it come with harmonica connector? Anything that it couldn't do? Any further info appreciated.
Last edited by RobMc1963$; Feb 3, 2021 at 02:29 PM.
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