Lost gauge lights and taillights

So, in constantly fooling with this truck , 87 GMC, I have managed to lose gauge lights and taillights. Headlights work, blinkers work, brake lights work. What did I unhook?

I hate to do this to you, but you checked your GAGE/IDLE fuse and your T/L CTSY fuse, yes? Assuming that’s okay, there maybe a pinch, fray, or some other kind of wiring mutilation in the taillight portion of the harness, specifically the running lights. Jerry’s looking so you’re in good hands.

Probably just blew the T/L CTSY fuse.

Heck I hope thats all it is, I will check tonite,just thought it was weird all other lights working.

Ok, so , found out tail light fuse blown, replaced it and that fixed that, but still no dash lights. Now, I installed an aftermarket radio about time this happened. I bought a harness specifically for our year trucks, but there were 2 wires not used off original harness, an orange and a brown wire, that plugged into old radio. Is this possibly my problem , and if so, what do they connect to? Thanks

Layne02 said:

Ok, so , found out tail light fuse blown, replaced it and that fixed that, but still no dash lights. Now, I installed an aftermarket radio about time this happened. I bought a harness specifically for our year trucks, but there were 2 wires not used off original harness, an orange and a brown wire, that plugged into old radio. Is this possibly my problem , and if so, what do they connect to? Thanks

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I want to say that orange was what they used for all the courtesy circuit power. (i.e. back lighting, dome light, cigarette lighter, ect.)

Hi I have the same problem except my T/L CTSY fuse melted in the fuse block. I was thinking of running a separate line through the firewall with a 20 amp inline fuse holder.

Jake Bouchard said:

Hi I have the same problem except my T/L CTSY fuse melted in the fuse block. I was thinking of running a separate line through the firewall with a 20 amp inline fuse holder.

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my T/L CTSY fuse melted in the fuse block.


That's exactly what fuses are designed to do.

Seriously, I'm sure you mean that the plastic casing (i.e. the colorful part that houses the fusible strip and associated stabs) somehow got wicked hot. So hot, that it "became as one" with the surrounding area of the fuse block. That should not ever happen.

There is either:

1. Something really wrong with your fuse block, or

2. You were sold a defective fuse (which BTW, would be the basis for a very lucrative lawsuit), or

3. Your are not being totally forthcoming with the facts. Look up the word "disingenuous". Never mind, here is the definition: not candid or sincere, typically by pretending that one knows less about something than one really does.

Can't you take something... like a little screwdriver and pick it out. Even if it comes out in a less than delicate manner - and the area around the slot looks bad when you're done - it doesn't matter. The front face of a fuse block's molded plastic case only serves to provide access to those copper clips (sometimes referred to as tulips) that the fuse stabs into. Also it is for printing the name of the circuit(s) the fuse protects.

As a rule, those female clips are set far back from the front face of the block that accidental contact with them is not possible - or at least very difficult. All the real work goes on in the back of the block. That is where the clips are securely held in their assigned places and the associated wiring is connected to them.

First of all, you have to see what you are dealing with. Just do it - get the remnants of the fuse case out of the slot and inspect the clips. They will almost surely be able to still accept the fuse stabs. If they seem to have lost a bit of their clamping power, take the little screwdriver (the same one that you used to remove the melted fuse case) and bend them inward towards each other.

If however, you do decide to pick the melted fuse casing out of the block, and find that the clips are severely damaged (burnt/melted to the point where they are not serviceable or able to hold a fuse), you have to find out what happened to cause that damage. Fuses hardly ever continue to allow that much current flow - to the point where they get so hot that they melt. Something happened with wiring behind the fuse block - not in the load side.

Good luck - and come back tell us what you are planning. Some of these guys are nice, and they'll help you figure out how to do a proper and safe repair.

Just getting back to this after working on a blinker problem. So back to the orange and brown wires that plugged into back of original radio. As I said before the harness I got to plug into new radio didnt use the two wires, and if the orange wire controls ctsy lights that may be what is keeping dash lights from coming on , but if it is, Im not sure what to do with that info. where would I reconnect wire ?? I hate wiring

Layne02 said:

Just getting back to this after working on a blinker problem. So back to the orange and brown wires that plugged into back of original radio. As I said before the harness I got to plug into new radio didnt use the two wires, and if the orange wire controls ctsy lights that may be what is keeping dash lights from coming on , but if it is, Im not sure what to do with that info. where would I reconnect wire ?? I hate wiring

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You didn't indicate what aftermarket H/U you are installing. But there is an international standard for aftermarket H/U wiring colors that should apply.

You probably already figured out the speaker wiring, so this will only deal with the remaining leads. On the truck side, other than the two speaker connectors (4 leads each), there is one connector with 3 leads (YEL, BLK & GRY) for switched power/ground/backlighting. There is also a 2 pin connector (ORN & BRN) that GM used to keep constant power on the clock. The BRN lead in the 2 pin connector was for clock illumination - it isn't necessary with modern head units. Don't connect it.

Here are the cross connections:

1. YEL (H/U) is constant hot from battery. Power for clock, radio presets, preferences, etc. Connects to ORN in harness

2. RED (H/U) is switched accessory power. Enables the H/U to power up when you push the ON button - and the key is in RUN/ACC. Connects to YEL in harness

3. BLK (H/U) is ground connection. Connects to BLK in harness.

4. ORN (H/U) is for illumination. Connects to GRY in harness.

5. BLU (H/U) raises power antenna when H/U is on. N/A - don't connect.

6. BLU/WHT (H/U) power to external amp. Probably N/A - don't connect.

A handy chart:


As far as your lack of cluster/HVAC control panel lighting, check the 5A fuse labeled INST LPS (top row 3rd, column inboard). If it is good, turn the parking lights on and use a VOM or test light to check for voltage into the fuse (line side should be the LH clip, but check both). If there is voltage there, check that the lead for the instrument lights is firmly plugged into it's socket. Those are the first steps.