Dash lights and instruments

Brian VT · Dec 14, 2021

My dash blinker lights work. The high beam light works. The battery picture light (lower left bar of lights) works.
The voltage gauge seems like it might be working. The fuel gauge is either full left or full right. The oil pressure and tach. guages do nothing. The heater/AC lights (in the center dash panel) don't work either.
The headlight switch turns on the headlights and will turn on the dome light if turned past the "click".

I removed the instrument cluster hoping to just change some bulbs and at least be able to see my speed at night.
Nope. All 4 bulbs are fine.

Could a bad headlight switch connector/plug affect all/most of these, including the heater panel?
Might the headlight switch itself be a culprit? What's the scoop on prices/brand of these? I'm seeing prices from $9 to $68.

Farmer Rock · Dec 14, 2021

Sounds like the headlight switch. I got my last one from Rock Auto, and I think I paid under $20 for it and it seems just as good as the stock ones.

Rock

Brian VT · Dec 14, 2021

Thank you.

franklin2 · Dec 15, 2021

On most of those cluster lights I find the bulbs are good also. You just have to push the bulb in and out a couple of times and it will start to work. Years of corrosion on the contacts I suppose.

catbird7 · Dec 15, 2021

Money well spent is the heavy duty headlight wiring harness from LMC. Wiring and electrical stuff is my weak area however even I had no problem installing it. Another good move is the 3g alternator upgrade. Both simple and both offer huge improvement over stock. The wiring harness will eliminate short service life of both the headlight switch and dimmer switch.

IDIBRONCO · Dec 15, 2021

I have to agree here. I had the same experiences including being a big electrical dummy (my description).

Brian VT · Dec 15, 2021

I will look into that in the future. Thanks.
For now I'd just like to know if my cluster is fried or if it's just the switch.

franklin2 · Dec 16, 2021

Brian VT said:
I will look into that in the future. Thanks.
For now I'd just like to know if my cluster is fried or if it's just the switch.

Your cluster is just a common mounting point for lots of different circuits in the truck. Besides poor connections and crumbling plastic, it never really "fries" or burns out.

There is a common blue with red stripe wire that comes from the headlight switch that feeds all the back lighting in the dash. You will find this wire running everywhere, and there is also one blue/red wire that feeds the large plug that is plugged into the cluster. This wire feeds all the backlighting in the cluster.

All you have to do is go buy a testlight, clip it to a good ground, and then with the headlights on, probe the blue/red that leaves the headlight switch and see if you have voltage. Make sure you twist the knob around to make sure it's on max brightness.

Brian VT · Dec 17, 2021

Yay. It was the switch. I now have dash lights (and the hvac console lights). Tachometer still doesn't work so that's my next project.
The headlight switch shaft fought me pretty well. I'm guessing it was happy being in there since 1987 and didn't want to come out.

Farmer Rock · Dec 17, 2021

Brian VT said:
Yay. It was the switch. I now have dash lights (and the hvac console lights). Tachometer still doesn't work so that's my next project.
The headlight switch shaft fought me pretty well. I'm guessing it was happy being in there since 1987 and didn't want to come out.

Glad you got it sorted out!
As for the tach, check the tach sender on the timing gear cover in front of the injection pump. Make sure those two wires aren't touching. If they aren't, you more than likely have a bad tach sender. I just replaced the sender on my 93 with one from my parts truck since the new units are pricey.

Rock

Brian VT · Dec 17, 2021

I had removed that tach. sender and tested it based on something I searched and found here.
I think the post said that if it had continuity then it should be okay. And it was.
I put it back in and did notice when I was screwing it in that a bit of fluid/bubbles was coming up through where the wires exit. I don't even know which fluid is in there.
I now have lights on the cluster but tach. still not working. I don't know if that slight leak at the top of the sender is the culprit. But I guess that's a story for another thread.

Farmer Rock · Dec 17, 2021

That would be oil leaking out of the tach. You can use rtv or a new o ring.

Rock

Brian VT · Dec 17, 2021

The O-ring looked ok and I smeared it with some oil before reinstalling. It's not leaking around the threads. The bubbling was coming up amongst the wires where they come out the top. I think the material that the wires come up through is called potting?
Anyway. I wouldn't think that would affect the signal being sent. But I am wrong often.

snicklas · Dec 17, 2021

Yes, that is the problem. Those are the signal wires, and the oil is shorting them out. Looks like that sensor will need replaced. But, hold your hat, they are cost more than you might think....

Dash lights and instruments

Brian VT

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Farmer Rock

just a fella' without a 10mm socket

Brian VT

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franklin2

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catbird7

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IDIBRONCO

IDIBRONCO

Brian VT

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franklin2

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Brian VT

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Farmer Rock

just a fella' without a 10mm socket

Brian VT

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Farmer Rock

just a fella' without a 10mm socket

Brian VT

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snicklas

6.0 and Loving It!!

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