Question: 1979 Dash Main Wiring Harness (w/Power Door/Locks or Wipers)

[KauaiCorvette]

My 1979 Corvette is in very original and well maintained condition, but... like several other posts I have been reading, it has interior light problems. The fuses seem to be in good condition, but all of the dash lights with the exception of the right turn indicator are not functioning. :confused Also, the courtesy light timer needs to be replaced as it has failed, but the courtesy lights it controls do work.

For the dash light problem, I am considering replacing all of the bulbs with a complete bulb kit from Zee ($35.), but I suspect more is happening. Possibly old wiring causing the problem. Has anyone replaced their Dash Main Wiring Harness before? How much trouble was it to replace? In this 32 year old Corvette, even though it has only 25K miles on it and been garaged, many wires seem brittle. As long as the replacement isn't too difficult, I can do this myself. At least that is what I am telling myself. :W But at $915.00 I would like to know what I am getting into first. Anyone?

 

[6880 Mike]

Do your instrument panel lights dim up and dim down when turning the headlight knob?

 

[KauaiCorvette]

Hi Mike,

Thanks for the reply. The dimmer control on the headlight switch doesn't work either. The only dash lights that function are the right turn signal flasher and the parking break light. Everything else is dark. As I mentioned in the post, I also need to replace the courtesy light timer, but it's lights still work. I checked the all of the fuses and they looked good, but I will replace them anyway to be sure. I was considering the new dash harness just because the wiring is 32 years old. But I do not know if I will need to remove the dash to do so. Any ideas you have would be appreciated as I really want to see the instruments at night.

 

[6880 Mike]

Sounds like you need a headlight switch and not a dash harness.

 

[KauaiCorvette]

Ya know Mike, I am glad you said that cause I was just thinking about that earlier today. But if you hadn't said it, I probably would have dismissed the thought. That's why I like this forum so much. People with experience helping others.

Mahalo!

 

[madrivers1]

Was it the dimmer switch?

I have replace my once already 10 years ago in my 79'. Now the dash lights will not come on. But I can use the dimmer to turn on the dome light. Just wondering if the dimmer switch fixed your issue. Like you I have check all the fuses.

Thanks,

Brian

Hi Mike,

Thanks for the reply. The dimmer control on the headlight switch doesn't work either. The only dash lights that function are the right turn signal flasher and the parking break light. Everything else is dark. As I mentioned in the post, I also need to replace the courtesy light timer, but it's lights still work. I checked the all of the fuses and they looked good, but I will replace them anyway to be sure. I was considering the new dash harness just because the wiring is 32 years old. But I do not know if I will need to remove the dash to do so. Any ideas you have would be appreciated as I really want to see the instruments at night.

 

[KauaiCorvette]

Hi Brian,

No, it was not the dimmer switch. It was the Center Console Circuit Board. These are amazingly fragile in old Corvettes. It controls all of the center gauges and lights. My corvette had the original stereo replaced with a CD stereo deck long ago and it is my feeling that the shop that did it caused the Circuit Board to be damaged. The damaged circuits were easy to identify. I then replaced it very inexpensively through Willcox. Once replaced, all of the dash and center console lights now work as well as a couple of the center gauges which I previously thought I would need to replace.

I also replaced a few of the bulb holders and all of the bulbs while I was in there so I would not need to go back soon. I'll wager dollars to donuts that you have a similarly damaged circuit board. Check out Willcoxcorvette.com in the Forum Specials and look under "Forum Dash Printed Circuit Board" for more information. There is a second Tach/Speedo Circuit Board, but I did not need to replace mine, as my Tach/Speedo both works. When I replaced the Center Console Printed Circuit Board, the dash lights at the Tach/Speedo began to work. Although there are also light circuits on the second board, replacing the center Circuit Board seems to have a connection to the Tach/Speedo side. Anyway, everything is working just fine now. I hope this was helpful. I was very happy not to have had to replace the dimmer switch because it seems like a lot of work.

 

[SVO]

To answer your question about replacing the main harness, it's a major job to do so. Your looking at pulling the dash, instrument console and console to replace the harness. But in my experience, if someone hasn't been under the dash hacking & cutting the harness or if there hasn't been an electrical event that let the smoke out of the wire, the dash harness tends to be in pretty good shape.

 

[Manu79c3]

1979 dimmer switch wiring riddle

Hi all, i read this thread with interest as i have recently acquired my first corvette, a 1979 c3. The dash lighting does not work, and i noticed a few issues with The steering column. So the dimmer actuator that was missing is now ordered. However, looking under the dash, i can't see any loose connector in the wiring that would plug into the dimmer switch mounted on the column. Reading your thread, i clicked that my dash mounted headlight switch actually has a turning knob. So, my question is :

Is the dash dimming on 79s via the dash knob, and the column mounted switch was redundant on the model ? Which would explain why i don't have a plug on dash wiring,

Or

It's via the column switch, my wiring has been savaged (there are a few loose wires under there :-( ), and the rotating knob is for something else ?..

Any guidance to a beginner appreciated! Cheers.

 

[Antz81]

The rotating knob on the light switch is the dimmer for the dash lights. If rotated far enough you should feel a click which will bring on the interior lights (and spare wheel light)
The dimmer actuator on the steering column is for the headlights. Its mounted on top of the column so may be a little hard to spot it and any wiring for it.

 

[bill81vette]

Welcome to CAC!!!
enjoy!!!

 

[Manu79c3]

Thanks heaps Antz81 and Bill81, this clarifies a lot. I'll chhase the dash dimming from another direction now. Forgive my ignorance (again), but im a little confused by headlight comment : are you saying that the dimming switch on the column that's actuated by turn lever via the dimming rod is for the headlights themselves ? Does that mean i can dim the headlights when they're up ? I don't get why, first car ive seen withit, any chance you can explain the logic behind that feature? Thanks again guys.

 

[Antz81]

Thanks heaps Antz81 and Bill81, this clarifies a lot. I'll chhase the dash dimming from another direction now. Forgive my ignorance (again), but im a little confused by headlight comment : are you saying that the dimming switch on the column that's actuated by turn lever via the dimming rod is for the headlights themselves ? Does that mean i can dim the headlights when they're up ? I don't get why, first car ive seen withit, any chance you can explain the logic behind that feature? Thanks again guys.

The dimmer switch on the column alternates the headlights between hi beam and low beam. nothing fancy.

 

[Manu79c3]

Eeeer, on mine, that's done via a foot switch. I was wondering why the wiring to the foot switch looked non standard, sound like that's the odd one out. Would also explain why i can't find the connector, already in use! So foot switch would be for earlier years correct?
Nothing like a good forum to stop the head scratching and make real progress, thanks so much!!

 

[Antz81]

Eeeer, on mine, that's done via a foot switch. I was wondering why the wiring to the foot switch looked non standard, sound like that's the odd one out. Would also explain why i can't find the connector, already in use! So foot switch would be for earlier years correct?
Nothing like a good forum to stop the head scratching and make real progress, thanks so much!!

Foot switch? That's a new one. Definitely a bubba job there. It should be controlled by pulling back on the turn signal lever. (This applies to all c3s 77+)

 

[Manu79c3]

OK, thanks for confirming Antz81 ! Explains some of the non standard wiring. I definitely want to return it to its standard configuration, but I have had some bad news today ; i thought i had sourced the dimmer rod actuator which is missing in my car, but the supplier that had it listed is telling me none available (the part I call actuator is the plastic part that fits between lever pivot and dimmer rod).

Does anybody know where i can source one from ? neither Ecklers nor Corvette Central have it listed either. Any suggestions from anyone please ?

Good learning for me here - Thanks again.

 

[Les Fetherkile]

Sounds like a bad headlight switch.

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