Instrument Cluster Gone Haywire

[Chicago Bluesmobile]

Tonight I reinstalled my repaired instrument cluster (bad speedo head) on my ‘74 Monaco and everything went great. I inadvertently touched the limiter while the car was running and noticed a quick flash of light from the cluster. Now when I turn the lights on the fuel gauge stops working, the ammeter light comes on, both turn signal lights stay lit and it looks like the drivers side of the cluster doesn’t light up.

Turn the lights off and everything goes back to normal.

Did I fry the voltage limiter or fry the circuit board?

 

[Davea Lux]

Voltage limiter only runs the gauges on this application, the gauges get their ground from the various sensors they are hooked to You would appear to have a bad ground to the cluster. Cluster lights are seeking a ground and the idiot lights are supplying it thru their filaments. Check the plug for the cluster if that is ok, you may need to pull the cluster and start looking for fractures in the circuit board, it will likely be found on the ground side of the dash light circuit. You can also grab a set of alligator clips and ground the cluster case to see if the idiot lights go out, this will usually confirm a bad ground.

Dave

 

[Chicago Bluesmobile]

Thanks Dave. Seeing as the cluster was working perfectly fine with the lights on until touching the limiter against the circuit board, I’m pretty sure I created a fracture in the circuit board. Pulling it back out tomorrow. Sigh.

 

[Justin Plant]

If you did fracture the board, its still available. I sourced one from a supplier on eBay. I don't remember the company name though.

 

[bigmoparjeff]

Sounds like you lost one of your grounds on the board and the electricity is finding alternate paths to ground causing things to light up that shouldn't be lit.

Also be wary of cheap LED bulbs. They can partially short out and cause strange electrical issues.


Jeff

 

[CBODY67]

On one of my cars, years ago, the body shop used butt connectors to reconnect the rh frt turn signal bulb wiring. Worked fine, but suddenly I started seeing a blowing indicator for that light on my instrument cluster. It would come and go, too! Finally got new plug-together connectors on that circuit and all worked well again.

Electrons will always seek the closest ground available, which can cause some flaky results, by observation.

CBODY67

 

[74Monaco CHP]

Thanks Dave. Seeing as the cluster was working perfectly fine with the lights on until touching the limiter against the circuit board, I’m pretty sure I created a fracture in the circuit board. Pulling it back out tomorrow. Sigh.

I put an entire new made modern circuit board in mine. The aux gauges would not work and I have a second. I found out that they went to ground. I added the proper new electronic voltage limiter.
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Pardon Our Interruption...

 

[CBODY67]

Did you rebuild or new-build the circuit board?

Just curious,
CBODY67

 

[Vinny]

Tonight I reinstalled my repaired instrument cluster (bad speedo head) on my ‘74 Monaco and everything went great. I inadvertently touched the limiter while the car was running and noticed a quick flash of light from the cluster. Now when I turn the lights on the fuel gauge stops working, the ammeter light comes on, both turn signal lights stay lit and it looks like the drivers side of the cluster doesn’t light up.

Turn the lights off and everything goes back to normal.

Did I fry the voltage limiter or fry the circuit board?

View attachment 733517

View attachment 733518

It sounds like a ground is missing.

 

[Milo]

I seen a guy solder a brake in his circuit board and that was a few years back and still working