Dash lights not working

[Bullett]

I am putting a new Skool dash guage assem. In my 62' c10. I am planning to use the original dash light circuits to feed the lights on my new gauges, problem is, none of the light bulbs work except for 2 of them. These 2 lights are the only 2 in the cluster that have the black plastic sockets. The rest are all metal type bulb sockets. The 2plastic ones that work go to a couple idiot lights in the factory cluster, don't remember which ones. These 2 bulbs stay lighted up 24/7, wether the light switch is on or not. They eventually drain the battery. O.k., back to my questions, why do these 2particular bulbs have a plastic socket compared to all the rest having steel sockets? What would be a best guess as to why the dash lights won't light up? The fuse in the fuse box looks good. All the rest of the lights on the switch work fine (headlights, tail lights, parking lights). Could the switch be bad even though the rest of the lights, except dash lights, are working? The wiring under the dash has certainly been whacked and hacked over the last 51 years but I didn't see anything real obvious. Any suggestions? Thanks

[ray_mcavoy]

The bulbs in the metal sockets receive their ground connection through the metal cluster housing. So they won't work if the cluster housing doesn't have a good ground connection due to surface rust, paint build-up, etc.

About 4 of the bulbs in the metal sockets will have gray wires ... those are the ones that illuminate the cluster. They receive power through the rheostat (variable resistor) that's built into the headlight switch. That is supposed to allow you to brighten/dim the cluster lighting by rotating the headlight knob. And yes, it is possible for just that section of the headlight switch to be bad and allow all of the other lights to work. Often it's just some dirt/tarnish on the rheostat windings so try cleaning them with some electrical contact cleaner.

A bad cluster ground or dirty/tarnished rheostat are just a couple of things that could be preventing the dash lights from working though. There could also be a bad connection somewhere in the circuit (rust/corrosion on the fuse clips for example). Or a broken/damaged wire. Using a test light or voltmeter to check for power at various points in the circuit is a good way to track down the problem.

As for the reason why some bulbs are in plastic sockets, it's because of the way those particular warning/indicator lights are wired. Many of them have a pink +12V supply wire that should only be live with the ignition on. The other wire usually leads to a switch that activates the light by completing the circuit to ground if the oil pressure is too low, engine temp is too high, etc.

[Bullett]

Awesome explanation, I have a better understanding now. I just sprayed the rheostat and the plug in connectors on the switch with lectra clean, I will let it sit for a bit and then see if it helped. I will also put some di-electric grease on the connectors. The more I touch the light switch, the more I'm thinking it is original equip. And maybe the issue. The plastic seems very brittle. I will post my progress, again, thanks for the explanation.

[Bullett]

After spraying with lectra clean and let sit for a while to dry, I had dash lights for a couple seconds and then they were gone and never to return. I am pretty much convinced it is the switch and I just ordered a new one. Should be here Wednesday. Now trying to figure out how to remove the old switch.

[ray_mcavoy]

Originally Posted by Bullett

Now trying to figure out how to remove the old switch.

Pull the knob all the way out to the "headlights on" position, reach up under the dash and push in on the little release button. That button should be on the side opposite the wiring connector. While holding that button in, you should be able to finish pulling the knob & shaft assembly straight out of the switch. Sometimes it takes a little wiggling or twisting to get it to pull free.

Once the knob & shaft are out of the way, you can unscrew the retainer nut that holds the switch into the dash. And finally, unplug the wiring.

[Bullett]

Great, thanks Ray. I screwed around with the dang thing for 20 minutes and still couldn't figure it out. Always much harder when you have yourself crammed under the dash, upside down. hee hee.

[Bullett]

Wired up my new cluster tonight, hopefully I have it wired correctly.


Just waiting for my new light switch to show up, then hopefully it will all come together. Do have another question though: the fuel sending unit currently has a wire that goes to the fuse block, can I just tee into that wire and run it to my fuel guage?

Thanks...bullett

[ray_mcavoy]

Originally Posted by Bullett

Just waiting for my new light switch to show up, then hopefully it will all come together. Do have another question though: the fuel sending unit currently has a wire that goes to the fuse block, can I just tee into that wire and run it to my fuel guage?

Lookin' good!!

Yes, you could tap into that junction point on the fuse box for the fuel sending unit wire.

However, you might not need to run the wire all the way down there ... the dash harness should already have a wire that runs from that point on the fuse box up to the socket where the original instrument cluster used to plug in. So you could plug the new fuel gauge sender wire into the appropriate terminal on the OE cluster socket.

[Bullett]

Originally Posted by ray_mcavoy

Lookin' good!!

Yes, you could tap into that junction point on the fuse box for the fuel sending unit wire.

However, you might not need to run the wire all the way down there ... the dash harness should already have a wire that runs from that point on the fuse box up to the socket where the original instrument cluster used to plug in. So you could plug the new fuel gauge sender wire into the appropriate terminal on the OE cluster socket.

That's a good point, just find the fuel sender wire in the original cluster and use that, will do. I'm slowly catching on with the wiring theory. Thanks again.

[ray_mcavoy]

You're welcome! In addition to the fuel sender wire, the original cluster socket will also provide you with the following wires that should come in handy for connecting in your new gauges.

These color codes are assuming your '62 originally had a warning light style cluster (not the optional full gauge cluster).

On the 4-terminal plug:

Dark Blue = RH turn signal indicator.
Light Blue = LH turn signal indicator.
Light Green = "COLD" light ... won't need this with your gauges.
Brown = fuel sender (this is the one that leads down to that tap point on the fuse box).

On the 6-terminal plug:

Light Green = headlight high beam indicator
Dark Blue = "OIL" light ... can be re-purposed for your oil pressure gauge sender wire. The end out on the engine will need to be moved over to the new sending unit of course.
Gray = cluster illumination ... can be used for the lights in your new gauges as you were originally planning.
Pink = +12V switched feed from ignition ... can be used to power the new gauges. Note: this wire isn't protected by a fuse from the factory so adding an inline fuse might not be a bad idea.
Dark Green = "HOT" light ... can be re-purposed for your temperature gauge sender wire. As with the oil gauge, the end out at the engine will need to be connected to the new sending unit.
Brown = "GEN" light ... won't need this with your gauges.

[Bullett]

Well, I definitely have the factory harness, all the colored wires are right on with what Ray said. unit
I installed the new temp. Sending unit that came with my new gauges. I went to swap out the oil sender and found they had a diff. Thread size.


I am assuming 1has metric threads and 1has standard. Tomorrow when I have more time, I will measure the threads and thread pitch more accurately to see exactly what I have. Seems to be about .022 difference in size. I am hoping the oil sender that was on the motor is going to work with the new guage. If not, gotta devise a plan B. Ray thanks for breaking down the colored wires and what they do. That makes this job all that much easier. Hoping my new light switch comes in tomorrow.

[Bullett]

Oh, BTW, my truck has a crate 350 engine, not sure why the oil sender threads are diff.

[Bullett]

O.k., after I got to measuring this morning, threads on both oil senders appears to be the same. The used sender measures a bit smaller just from being used.

[Bullett]

Good news and bad news. Bad news first, appears that I bought a new light switch that I didn't really need, dash lights still don't work. Good news is, through all my flailing around, I figured out when I hold most any of the dash lights up against the metal trim ring on my ignition switch, they light up.

I am assuming this points to a grounding issue. If so, what is the best way to ground the dash light harness? Thanks for any help....Bullett

[ray_mcavoy]

Originally Posted by Bullett

... I figured out when I hold most any of the dash lights up against the metal trim ring on my ignition switch, they light up. I am assuming this points to a grounding issue. If so, what is the best way to ground the dash light harness?

Yes, if you are going to use the original metal sockets they need to be snapped into holes in a grounded metal panel.

However, from your earlier pics it looks like your new gauges have their own light sockets & associated wires. So you could eliminate the original metal sockets and splice the stock gray wire(s) to the illumination wires on your new gauges. Then connect all of the bulb ground wires from the new gauges together and hook them to a convenient ground point somewhere under the dash.

[Bullett]

Oh, o.k. I'm learning. So the metal socket light bulbs originally got their ground from the grounded dash panel they sat in. I had planned on cutting off the sockets and using the gray wires to power up the lights in my new gauges, but I guess I was thinking that before I could do that, I had to get the old lights to work first. So it sounds like as long as my new dash has a good ground, I should be good to go. I should hopefully get a chance to do this tomorrow, I will post a couple pics of the finished product. Thanks again Ray.

[Bullett]

I have everything hooked up. Yeah! , all the gauges appear to work. The bad news is that none of the gauge lights work.?? I used the gray wires that had lighted bulbs in them before I cut the sockets off.

Not really sure what to do from here. Any suggestions appreciated. Thanks.

[Bullett]

Oh, forgot to add, the high beam indicator light works but the blinker indicator lights don't. I am guessing because the original dash didn't have blinker indicators? As someone mentioned, I could probably chase the wires that go out to my blinkers on the hood but won't pursue that until I get everything else working.

[ray_mcavoy]

Since you've already established that the gray wire(s) are providing power as they should, it sounds as though you may still have a ground problem with the lights.

The only other possibility that I can think of would be if your new gauges have LED lights instead of regular incandescent bulbs. With LEDs the polarity is important ... they won't work if the positive & negative are reversed.. The positive side should be connected to the gray wires and the negative to ground.

Edit: just noticed your update ... The fact that the high beam indicator works is a good sign and means that it must have a good ground. Did you connect all of the gauge light grounds to that same point?

As for the turn signal indicators, did your original cluster plug have the light & dark blue wires on the 4-terminal connector or were those cavities empty? If those wires were present, they should already be tied into the front turn signal lights. That's assuming the wiring hasn't been altered though ... might be worth tracing those wires back to make sure they're still connected on the other end.

[Bullett]

The lights only have 1 terminal for the lighting. If I take the wire I have on any of the gauge light terminals and unplug it from the gray wire and then touch it to the power terminal, with the key on, that specific gauge light will work.

[jtrichard]

do you have a test light? best way to check if you have power sounds like you have a ground problem still ......as for turn indicator i believe that OEM had one only for both sides

[Bullett]

I put my volt meter on any of the gray wires, with the light switch on, and even the key turned ahead, there is no power to any of the gray wires. I will take another good look after I have dinner. The gray wires had power. The only thing I did that throws a wrench into it is that I removed the previous volt gauge that was mounted to the underside of the dash. That gauge seemed to have more wires attached to it as I would think needed.

[jtrichard]

you could have popped the dash fuse in the block

[Bullett]

Would there still be power to the ignition terminal of the gauge if I popped a fuse? Isn't that the same fuse?

[jtrichard]

this might help looks like they used 2 wires left and right to a single bulb for turn indicator http://67-72chevytrucks.com/vboard/s...d.php?t=509522