Dash Panel Issue

[Classics Fan]

Before I pull the dash panel in my 71 Jimmy I’m hoping someone has some ideas of what to look for to fix the problem I’m having.

When I bought the Jimmy in late 2018 it had an intermittent problem where, when the headlight knob was pulled out, the panel lights would go dim, the high beam indicator would illuminate when the headlights were on low beam (and would go out when they were out on high beam), and both left and right turn indicators would glow. In this condition when the turn switch was flipped in either direction the corresponding dash indicator would flash off and on (normal operation is the indicator is unlit until activated and then flashes). Until recently a rap or two with knuckles on the top front center of the dash panel would fix the problems. However this isn’t the case any more. All the conditions I’ve described are now constant and not intermittent.

My thought is either the printed circuit has a problem, there’s some sort of short in the circuit, or a bad ground. Anyone run into this before? Thoughts, ideas or suggestions?

[franken]

There should be a ground jumper from the headlight switch or the PCB to the dash. It's been many years since mine was apart so I don't remember exactly where the jumper attaches.

[Classics Fan]

Thanks for the heads-up, franken. Seems like a possible likely source of my problems. I’ll look for this ground when I have time to pull the dash in the next couple of weeks.

[1970cstblazer]

There is a clip-on ground wire in the vicinity of the rear of oil pressure gauge. That's the only one I recall on my 1970 Blazer.

[hemi43]

This truck is over 50 years old. Do yourself a favor and buy a new harness.
I still shake my head how people will spend $50K restoring a vehicle and not upgrade the wiring. The insulation on those wires is long past it's due date.
I hope your truck has fire insurance.

[Classics Fan]

Originally Posted by hemi43

This truck is over 50 years old. Do yourself a favor and buy a new harness.
I still shake my head how people will spend $50K restoring a vehicle and not upgrade the wiring. The insulation on those wires is long past it's due date.
I hope your truck has fire insurance.

How difficult is it to replace the harness on an assembled vehicle? My impression is this is best done during restoration when it is disassembled.

[Classics Fan]

Originally Posted by 1970cstblazer

There is a clip-on ground wire in the vicinity of the rear of oil pressure gauge. That's the only one I recall on my 1970 Blazer.

I’ll look for this. Thanks!

[1970cstblazer]

One question I have with new reproduction harnesses for these trucks. Do they use a soy based insulation that attracts rodents to gnaw and chew the wiring like vehicles made for the last 30 years?

[1970cstblazer]

Originally Posted by Classics Fan

How difficult is it to replace the harness on an assembled vehicle? My impression is this is best done during restoration when it is disassembled.

Frankly, it really isn't too bad. The forward light harness and under hood engine harness are pretty easy. The dash harness requires the cluster and glove box to be removed to gain access to all of the retaining points and connections.

[hemi43]

Originally Posted by Classics Fan

How difficult is it to replace the harness on an assembled vehicle? My impression is this is best done during restoration when it is disassembled.

Very easy. Taking out the old one is the difficult part. If you don't have any stubborn screws or connectors, the dash wiring can be replaced in an afternoon.

[hemi43]

Originally Posted by 1970cstblazer

One question I have with new reproduction harnesses for these trucks. Do they use a soy based insulation that attracts rodents to gnaw and chew the wiring like vehicles made for the last 30 years?

That was years ago and hopefully they learned their lesson.
If you use a quality harness like American Autowire you will have no issues.
I would recommend upgrading the switches that come with some of the kits because I've had a few issues with them over the years, especially with the floor dimmer switch.

[Classics Fan]

So to close this thread: today I pulled the panel, replaced all the original incandescent bulbs with new LEDs, and made sure the two ground screws on the printed circuit were clean and tight. There is a ground wire from the back of the panel to the metal dash. One end looked suspect so I replaced that. The end result when everything was put back together is a brightly lit panel that functions as it should. Thanks to everyone who contributed with suggestions on what to look for!

[1970cstblazer]

Good deal