cluster lights not working?

[carlisle72]

hello,
just replaced the circuit board for my instrument cluster. gauges are working but none of the bulbs. tested and have power in wire harness going to the cluster but no lights working? Any suggestions to what to look for? oh, old one was working but looked really worn, so i replaced it. should have left well enough alone. i even put the old one back on same problem.

1972 chevy
thanks

ps check fuses look good

[Longhorn 70]

Headlight switch? Fuse?

[shawno72]

Probably one of the bulb holders isnt seated right. Make sure you ground the circuit board to the rear tin. My new circuit board wasn't missing the hole for the screw like my original one had.

[carlisle72]

headlight switch is new, fuses look good. the new circuit board had all the same screws the old one had. is there a way i need to ground the circuit boad to the tin?

[shawno72]

Only with the screws from the old one.
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[AirSpeed]

Have you tried turning the headlight knob? Maybe the dimmer is turned off, try turning the knob all the way.
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[carlisle72]

yeah dimmer is not off. hazard lights/flashers won't light up either. i've tested with my test light and i've got power on the circuit board at the bulb, like at the hazard lights, test lights up everytime it blinks but bulbs not lighting. seems like it could be a grounding issue, but i can't figure it out.

[Longhorn 70]

for grins clip your test light to ground and the probe end to a metal spot on the cluster.... see what changes or if the test light glows..

[carlisle72]

i just ran the test light to the ground side and nothing, it didn't light and the bulb didn't light either. i'm so lost and aggravated with this.

[Longhorn 70]

I am betting that if you did the probe between a ground and the metal on the panel and nothing lit, grounds aren't your problem.

If you had a bad ground and had the lights on and connected that way, you'd see a glow in the test light filament as there would be a difference in potential. If you have a volt meter you can verify that too... Red to panel ground and black to good chassis ground. You should see just a few millivolts. There should be a black 18 ga. wire on the panel that is ground too.

I'd still check the light switch...........for grins.

[VetteVet]

With the light switch on check for 12 volts on each end of the panel lights fuse in the fuse panel. Make sure the headlight switch knob is fully on bright.

If you get 12 volts there then check the gray wires on the cluster plug on terminal 8 for 12 volts or bright test light.

If you get 12 volts there then check for 12 volts between the gray wires and the black wire on terminal 7. This is the ground wire to the cluster. If you get these numbers then the power feeds to the cluster are ok and Your circuit board and cluster are probably not grounded.

look at the picture and just to the left of the cluster plug in you can see a small screw. This grounds the circuit board to the cluster and then you have to ground the cluster to the cab at a good ground for the lights and gauges to work. There is another one that is just above the speedometer on the right as well.




Here is the wiring to the gauge style cluster plug.

[wgr2112]

Is the back panel of the cluster painted? Shouldn't be an issue but the paint MAY prevent good metal to metal contact.

Just a thought.

[carlisle72]

Originally Posted by VetteVet

With the light switch on check for 12 volts on each end of the panel lights fuse in the fuse panel. Make sure the headlight switch knob is fully on bright.

If you get 12 volts there then check the gray wires on the cluster plug on terminal 8 for 12 volts or bright test light.

If you get 12 volts there then check for 12 volts between the gray wires and the black wire on terminal 7. This is the ground wire to the cluster. If you get these numbers then the power feeds to the cluster are ok and Your circuit board and cluster are probably not grounded.

look at the picture and just to the left of the cluster plug in you can see a small screw. This grounds the circuit board to the cluster and then you have to ground the cluster to the cab at a good ground for the lights and gauges to work. There is another one that is just above the speedometer on the right as well.

Attachment 1086624


Here is the wiring to the gauge style cluster plug.

Attachment 1086625

don't have a volt meter yet. i did use the test light and got a good light at the panel fuse and the gray wires. not quite sure what you mean about between the gray wires and the black ground wire. nothing on test light on the ground wire. have a ground wire running from housing to clean ground and still nothing.

[slikside]

Subscribed.
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[tsali39]

Same problem here. I have two lights ( speedo ) but no lights at the gas gauge. I am about to led the whole unit and be done with it!

[VetteVet]

If you look at the second picture in my post above You can see the gray wires and the black wire in the cluster plug. You can check power on the gray wires with your test light by going between the gray wires and any ground, with the headlight switch on.

There are no lights for the fuel gauge. It gets it's light from the 2 lights on each side of the gauge in the cluster. The two lights below the gauge are for the temp light and the brake warning light which have their own power sources.

Here is another diagram of the circuit board. The orange wires are the grounds for the dash lights and the gray wires are the power wires.Notice that the gray wires go to no.8 on the terminal connector and the grounds go to no.7
These are the two points I was talking about checking for 12 volts on the plug.

[carlisle72]

yeah i got power at the points you stated. when using my test light i used the black wire as a ground and tested the gray wires and got a light, so it seems the black ground wire is grounded.

[VetteVet]

If you've got power at the cluster plug on the gray wire then the only thing left is the plug and pins on the cluster. Unless the lights are all bad or their sockets are not making contact with the circuit board. If your gauges are working then the cluster is grounded so the power pin must not be making good contact. VV

[carlisle72]

thanks longhorn and vettevet for all your help. a word to the wise, if you ever replace your light sockets on your instrument cluster make sure the connectors are not totally laying flat. hahaha, after all that work and testing stuff and tearing into everything the connectors on the sockets were not bent upwards and making connection to the circuit board. but i learned a few things about chevy instrument clusters and tearing into a dash so atleast i learned something. thanks again guys.

Paul

[Longhorn 70]

Good job Paul! Glad you got them going.

[wgr2112]

Good to know!

I have a large pile of bulbs and sockets. I've tested all of them and they can be finicky about the way the bulb sits in the socket as well.

[dirish]

I learned alot!
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[Longhorn 70]

Just for grins I was going to add this image but since it was solved.....

It may help some to get LED lights to work. I made it for my reference. I marked polarity on it in thoughts of making my own LED bulbs. I didn't think they'd be as cheap as they are on eBay. Go figure..... Here it is.