No dash lights

[Logan306]

I have a 1994 k1500 I have no dash illumination lights, gauges work dummy lights work, hvac and radio. Fuse is good bulbs are good what could it be?

 

[Road Trip]

I have a 1994 k1500 I have no dash illumination lights, gauges work dummy lights work, hvac and radio. Fuse is good bulbs are good what could it be?

Greetings Logan306,

Welcome to the GMT400 forum! I'll give you a taste of how they document that illumination
circuit in the FSM (Factory Service Manual) ...followed by some troubleshooting tips. And at
the end I'll show you where the manuals can be downloaded for free.

****

Alright, I opened up the .pdf file for the '94 Electrical & Diagnosis FSM, and found this first
diagram to be helpful:

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My initial takeaways are:

* The gauges are powered by the 20 amp 'GAUGES' fuse. But the 'illum lights' get their power elsewhere.
* Looks like I need to chase down the "Instrument Panel Dimming" circuit for more info?

The next thing I found was a quick blurb about the Dimming Circuit:

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* OK, so the 5 amp "PNL LPS" fuse is what feeds this circuit? If you haven't already checked this, then see what you got?

Now if the fuse if blown, we need to figure out why? Or, if the fuse isn't blown, then where to next?

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Power flow is: 20A 'PARK LP' fuse > Light Switch > Adjustable Dimmer Switch > 5A 'PNL LPS' >
(S)plice 217 > C203 > Instrument Cluster Printed Circuit > Illumination Lamps > C203 > (G)round 202.

Alright, now you can make some careful observations to help narrow down exactly where this
circuit is broken. For example, if I read your problem description correctly, the lights on the radio and
the HVAC controls still work, even though the illumination lights in the instrument panel don't.

If this is correct, then it tells me that power made it all the way down to Splice 217, through the
working radio & HVAC lamps, back through the Ground splice S207, and finally G202.

So why did I drag you through the circuit feeding the working lamps? A: Because if you go back to
the circuit above, it neatly brackets where you need to look the closest. (S217 to C203, tracing the
printed circuit to the bulbs in question, back to C203, and over to the ground Splice 207.

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And here's some wiring diagram detail on connector C203:

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NOTE: If the gauges are working properly, then this means that the '150' ground circuit for the illumination bulbs is good?
If so, then I would be focusing on the +12v side of this circuit.

****

The above should give you a good starting point on troubleshooting the missing lights.

But there's a lot more info where that came from. If you don't already have the '94 Service Manuals,
then please go here and arm yourself for success: '88-'98 Service Manuals

Let us know what you discover, so that others troubleshooting a similar issue can learn from your experience.

Best of luck!

Cheers --

 

[Logan306]

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I’ve since taken the cluster off and found that’s the circuit is a bit melted can I fix this or do I need to get a new printed circuit for the cluster?

 

[Road Trip]

I’ve since taken the cluster off and found that’s the circuit is a bit melted can I fix this or do I need to get a new printed circuit for the cluster?

If it was me I'd try to fix that trace first, and only if that didn't work my backup plan would be to purchase a new printed circuit.
Here's a closeup of the area marked up to show where I would cut the damaged trace out of the circuit, and
how I'd route a short piece of 18-gauge wire from bare copper to bare copper:

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Instead of trying to work through the clear nonconductive layer, I would instead take
a small bit of 2000 grit paper & burnish both exposed copper contact pads where the
wire is going to go. Clean afterwards with a Q-tip and denatured alcohol.

Strip the wire on both ends, pre-tin both ends, and the pre-tinned wire should solder neatly
to the traces quickly and without any heat damage. (Make sure to position/solder the wire in
such a way as to leave enough physical clearance to avoid interference with installing the bulb
carrier or inserting the main connector into the cluster socket.

NOTE: I don't normally see damage like this, so I wouldn't risk using these same bulbs post-fix.
(Are the bulbs correct but the trace was scratched by the PO? Or is there an internal short
inside one of the bulbs causing excess current to overheat the weakest spot in the printed circuit?

Instead, I would order a 6-pack of the correct bulbs and start fresh with all new.
FWIW, here's what I found on my '99 instrument panel. Yours might be different, but possibly you
can get some additional info out of this: Replacing illumination bulbs on my instrument cluster

****

The backup strategy if it won't fix (or you decide to just go with new parts) would be something
like this: '92-'94 printed circuit for sale.

Thanks for your status report with the clear photo of the failure. Be sure to come back and
post your final fix for others to learn from.

Best of luck.

Cheers --

 

[Logan306]

I will give that a try thank you