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Old 03-13-2019, 01:28 PM   #1
Coalkracker
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Help with dash lights

Im trying to knock off the checklist one by one on my 70 c10 that i bought a few years ago and the next thing i need to figure out is my dash lights. The gauge lights, turn signal indicators, and the heat control do not light up. Where do i start trobleshooting this? The switch or the fuse panel? The headlights dont work too so im hoping just the switch but i dont want to rule anything out.
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Old 03-13-2019, 02:13 PM   #2
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Re: Help with dash lights

Maybe the dimmer switch?
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Old 03-13-2019, 04:38 PM   #3
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Re: Help with dash lights

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Originally Posted by Coalkracker View Post
Im trying to knock off the checklist one by one on my 70 c10 that i bought a few years ago and the next thing i need to figure out is my dash lights. The gauge lights, turn signal indicators, and the heat control do not light up. Where do i start trobleshooting this? The switch or the fuse panel? The headlights dont work too so im hoping just the switch but i dont want to rule anything out.
The first place to start is acquiring a year specific wiring diagram that illustrates wiring color codes. Given the amount of circuits that are involved, there is probably more than one problem. The first electrical items to check is always the fuses and grounds... As an example -- the dimmer switch has nothing to do with the dash light failure. Except for a faulty cluster ground, the dash light failure has nothing to do with the turn signal indictors.
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Old 03-13-2019, 04:43 PM   #4
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Re: Help with dash lights

I wasn't sure if it would affect the dash lights, but it will cause the headlights to not work
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Old 03-13-2019, 04:45 PM   #5
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Re: Help with dash lights

I checked the fuses and nothing was blown. I am not getting power to the fuse for the dash lights with the key on.
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Old 03-13-2019, 06:33 PM   #6
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Re: Help with dash lights

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I checked the fuses and nothing was blown. I am not getting power to the fuse for the dash lights with the key on.
Key doesn't have to be on for the dash lights to work.. Do you have a wiring diagram?? I'm not the type who "spoon feeds" information. My teaching method requires RTFM technique..

Here's a clue to dash light operation.. Although the dash lights operate from the headlight switch, they don't receive power from the headlight circuit. But a certain switch does have to be "turned on" before you will see power on the dash light fuse.. The wiring diagram will sort this out for you..
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Old 03-13-2019, 07:30 PM   #7
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Re: Help with dash lights

I have A diagram but im not sure if they were wired the same for all years and if they werent then im not sure what year its from.
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Old 03-13-2019, 07:33 PM   #8
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Re: Help with dash lights

I can see that the gauge lights are running off of the grey wire from the fuse panel. But im not sure where the power comes from to give the grey its power on the other side of the fuse.
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Old 03-13-2019, 07:42 PM   #9
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Re: Help with dash lights

Actually now that im looking at it my cluster harness does not match my diagram i have.
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Old 03-13-2019, 10:01 PM   #10
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Re: Help with dash lights

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I have A diagram but im not sure if they were wired the same for all years and if they werent then im not sure what year its from.
The wiring is similar from year to year, BUT there are differences.. Determine the year you're working with and get the corresponding diagram.. Grey is the color of the dash light circuit for most years of all GM products.. Referring to the proper diagram, trace the wire (no matter the color) on the other side of the fuse that has the grey wire on it.. I know where it goes, but, as I said-- I don't spoon feed.. You'll not learn a thing unless you dig into it yourself.. Turn on the dash lights (even if they don't come on) and check for voltage at the other end of that wire feeding the dash light fuse.. Do that and come back and tell me what you find..
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Old 03-13-2019, 10:08 PM   #11
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Re: Help with dash lights

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I can see that the gauge lights are running off of the grey wire from the fuse panel. But im not sure where the power comes from to give the grey its power on the other side of the fuse.
Think about what you just said (typed).. You know the answer, you're just not seeing it.. When everything is functioning properly, what does one do to make the dash lights come on??? the power for the dash lights comes from whatever device is activated..
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Old 03-13-2019, 10:18 PM   #12
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Re: Help with dash lights

Sounds like your hinting toward the headlamp switch?
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Old 03-13-2019, 10:30 PM   #13
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Re: Help with dash lights

One thing i did notice after i took my gauge cluster out this evening is that i had voltage on the grey wire. I grounded my meter to steel, not the ground wire in the cluster harness because i wasnt sure which one was the ground. So possibly the ground wire in the cluster harness is my problem?
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Old 03-13-2019, 11:00 PM   #14
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Re: Help with dash lights

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Sounds like your hinting toward the headlamp switch?
BINGO!!!! Now, you said some other lights don't work either --- headlights I believe.. Do the the tail lights work??? If so, that rules out a loss of power to the headlight switch.. If the tail lights do not work, then check for battery power (not switched but protected by a fusable link somewhere under the hood) to the headlight switch.. If you have power to the switch, the problem is under the dash or possibly a defective headlight switch.. Don't just run out and buy a headlight switch.. Find the actual problem and fix it.. Just like the charging system problem you had --- a possible corroded connection....
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Old 03-13-2019, 11:07 PM   #15
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Re: Help with dash lights

Yes the tail lights work.
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Old 03-13-2019, 11:23 PM   #16
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Re: Help with dash lights

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One thing i did notice after i took my gauge cluster out this evening is that i had voltage on the grey wire. I grounded my meter to steel, not the ground wire in the cluster harness because i wasnt sure which one was the ground. So possibly the ground wire in the cluster harness is my problem?
I missed this post of yours on my last read.. Yes, you're correct, it could be a bad ground connection.. In my first post in this thread, I alluded to checking fuses and grounds as the first first step.. You can "rig up" a temporary cluster ground wire for test purposes.. Get a piece of 16 - 18 ga. wire about a foot or so long.. Attach an open ended terminal eye on one end and a small alligator clip on the other.. Loosen one of the screws that attach the printed circuit to the cluster housing.. Select a screw that passes through one of the traces.. Loosen the screw and slip the terminal eye under it and tighten (do not over tighten.. Attach the alligator clip to a suitable bare metal location.. If the factory ground is bad, your temporary ground hookup will provide a ground path and the dash lights should now work..

I don't like the factory ground for the cluster.. It's comprised of a wire with a "J" clip on the end.. the "J" clip is attached to the edge of the steel dash on the edge of the cluster opening.. Given 40 - 50 years of vibration, rust, and general poor design, the ground becomes ineffective.. Loss of ground paths account for about 80% of the electrical problems in old vehicles..
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Old 03-13-2019, 11:34 PM   #17
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Re: Help with dash lights

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Yes the tail lights work.
OK.. This tells us the headlight switch has power to it.. At this point I wouldn't condemn the headlight switch.. As I previously stated, you have more than one problem. I'm leaning toward more corroded connections and poor/missing grounds. Let's get the dash light problem solved, then we'll move on to the other light problems..

While you have the cluster out, check the printed circuit "fingers" where the harness plugs into it.. Polish and tweak the contacts on the harness plug, making sure you have tight and clean contacts.. A pencil eraser makes a good polishing tool for those fingers on the printed circuit...
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Old 03-14-2019, 10:21 AM   #18
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Re: Help with dash lights

I checked the ground and its fine. Lights still didnt come on. I found a few bulbs that were burned out, one bulb holder has a broken contact, and a few other bulbs have corroded terminals coming out of the glass. One bulb holder is missing also. I have to go to the parts store and get some bulbs and hopefully bulb holders but i doubt they will have those.
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Old 03-14-2019, 10:59 AM   #19
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Re: Help with dash lights

Well ive gotten 3 bulbs to work so far...
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Old 03-14-2019, 01:53 PM   #20
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Re: Help with dash lights

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Well ive gotten 3 bulbs to work so far...
While we're at it, let's get the nomenclature correct.. It's not "bulb holder", it's bulb socket.. You're making good progress.. Using a small pick or screwdriver, gently lift the contact tabs a small amount on the bulb sockets and polish them with fine sand paper or a pencil eraser. Also, polish the printed circuit trace where the bulb sockets make contact with it. This will create a nice tight connection for the bulbs.. Just remember --- all the bulbs are not dash lights.. Some of those bulbs are for turn signal indicators, warning lights, and one is the hi-beam indicator.. Clean and polish all of them.. No telling how old those bulbs are.. I suggest you replace all of them..

You're doing good work.. When you get all the dash lights working, we'll move on to the next problem...
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Old 03-14-2019, 02:07 PM   #21
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Re: Help with dash lights

I had the parts store order me a few sockets since a few were in bad shape and broken. They are only a buck a piece so no big loss. I will have them tomorrow. I replaced the bulbs with some led's since i have a bag of them already. Cant see what they look like yet though because its too bright outside. If i dont like them i will get the filament type. I already polished everything on the printed board so i should be good to go with that. I think when i hit the turn signal i did not get an indicator lit up but cant confirm that right now. Once i get home i will mess with it some more.
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Old 03-14-2019, 02:33 PM   #22
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Re: Help with dash lights

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I had the parts store order me a few sockets since a few were in bad shape and broken. They are only a buck a piece so no big loss. I will have them tomorrow. I replaced the bulbs with some led's since i have a bag of them already. Cant see what they look like yet though because its too bright outside. If i dont like them i will get the filament type. I already polished everything on the printed board so i should be good to go with that. I think when i hit the turn signal i did not get an indicator lit up but cant confirm that right now. Once i get home i will mess with it some more.
As I stated before, Let's tackle and solve one problem at a time.. Get the dash (gauge illumination) lights working properly, then we'll move on to the turn signals..

This is just my opinion on LEDs.. Personally I don't like them, but to each his own.. I'd suggest you get all the lights working with conventional incandescent bulbs first. Sometimes certain LEDs can be problematic.. Get the circuits working first, then make the switch to LEDs.. This could prevent a lot of "tail chasing" on your part..

I'll be spending a lot of time today working on my truck.. However, I'll periodically check in on your progress..
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Old 03-14-2019, 02:57 PM   #23
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Re: Help with dash lights

X2 on the led's get them working first with regular bulbs then switch.
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Old 03-14-2019, 05:29 PM   #24
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Re: Help with dash lights

Ok so i have all of the gaige lights working. I have the flashers working too. Also the turn signals sort of work. They work when you move the handle up or down until it clicks then they go out. Im hoping the switch may just need to be cleaned but im not sure how to get into the column yet.
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Old 03-14-2019, 06:07 PM   #25
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Re: Help with dash lights

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Ok so i have all of the gaige lights working. I have the flashers working too. Also the turn signals sort of work. They work when you move the handle up or down until it clicks then they go out. Im hoping the switch may just need to be cleaned but im not sure how to get into the column yet.
It could be the steering wheel is setting just so and the cancel cam is turning off the turn signal switch.. Rotate the wheel a few degrees and see if the turn signal switch holds position.. Don't remove the wheel to do this.. Just turn it a few degrees just as you would while driving down the road. The switch isn't very "serviceable", meaning you can't disassemble the switch for cleaning.. If this doesn't get the turn signals working, let's leave them for a while as you may be looking at inner column work.. Let's move on to those pesky headlights..
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