What the heck is this on the back of my instrument cluster? (1 Viewer)

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Oct 15, 2022
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Saint Simons Island GA
Trying to figure out why my fuel sender isn't working and discovered this. Any ideas? Some sort of resistor?
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Looks like some sort of PO wiring hack job to me. Poor job of scraping "Grounds" for the instrument light bulbs. You should be looking for the wiring diagram that correct for your year, model and market. Search around here, there are threads for the amp meter / fuel gauge step down power supply.
 
Just guessing. Appears me that long yellow air is going to one side of your temperature meter. Further - it appears to me that circuit going to that long yellow wire and its bolt - have been physically separated ( open circuit).

The other end of that box has a discolored white/black wire —- that looks like it was soldered to the circuit board. Which just above that solider joint another line was scared into the circuit line.

If your temp gauge works - that box is either pushing the voltage up or down.

That is a mess.
 
Looks like some sort of PO wiring hack job to me. Poor job of scraping "Grounds" for the instrument light bulbs. You should be looking for the wiring diagram that correct for your year, model and market. Search around here, there are threads for the amp meter / fuel gauge step down power supply.
I put a 5” wire shunt on my amp meter for a 65 amp alternator
 
Just guessing. Appears me that long yellow air is going to one side of your temperature meter. Further - it appears to me that circuit going to that long yellow wire and its bolt - have been physically separated ( open circuit).

The other end of that box has a discolored white/black wire —- that looks like it was soldered to the circuit board. Which just above that solider joint another line was scared into the circuit line.

If your temp gauge works - that box is either pushing the voltage up or down.

That is a mess.
For sure PO hacking. I'm replacing the entire harness on my rig as there is evidence of a fire, missing fuses, and now, looks like the cluster. Yay!

I have an external temp gauge that I wired in, using a seperate sending unit- the cluster gauge reads much higher than my aftermarket. I've confirmed my aftermarket gauge is closer to reality with a laser thermometer. No idea what the PO was trying to do here.

I did get a really good deal on the truck, but had I known and done a better job of diligence, I would have prepared myself for this sort of ****ery.
 
rare person to pull the gauge cluster when buying a FJH40. I've got three things left on my rig that I need to get my arms round before I chase the hills. these old trucks always have a story.
 
That looks like an aftermarket 7v regulator. $57 from NAPA so don't toss it.

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The fuel gauge has a 7v regulator in it that will fail, people add an external regulator for the fuel and temperature gauges. This detail is usually not on the electrical schematic but have seen it in an FSM.
 
here:

1720558827058.png


from this awesome thread:

 
I didn't realize the instrument cluster wasn't 12volts ( sorry about the double negative). so, I suppose I can understand using a 7 volt regulator; but, way insert that device into and onto the circuit board. there are easier and less destructive ways to accomplish that work around.

The cold solider joints directly the circuit board still bug me.
 
My 7v regulator failed years ago and have been using a 7808 3 pin regulator attached to the back of the cluster for several years. 50 cents vs $50.
 
I have a couple of devices from Amoron, they let me regulate the voltage down to what I want. The goal was power my electric gloves(7.something V) off the 12 volt system, that way I could use the gloves batteries when away from the vehicles Elsie, F150 or the 4 wheeler.
 

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