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-   -   Yet another fuel gauge question (http://www.ifsja.org/forums/vb/showthread.php?t=187395)

Bkgw 06-24-2019 06:53 PM

Yet another fuel gauge question
 
I just re installed my 82 wagoneer fuel tank with brand new sending unit and the gauge still is not working. I cleaned the groumd at the rear of the frame and gauge still reads empty. I am not good with electrical diagnosis at all. I tried to ground the it from the sending unit directly and nothing. The gauge always reads empty. I replaced the 3a fuse and no change. The temp gauge doesnt seem to work either. I pulled the cluster and tightend things and the circuit board looks good. Any ideas on what else to try?

tgreese 06-25-2019 11:53 AM

Before going into specifics, I recall the TSM has instructions for testing the fuel gauge. It's in the Electrical section. If the gauge does not move off of empty, the sender circuit could be open, or the gauge itself could be kaput. You can test each of them separately with your multimeter and a few resistors. The manual calls for a fancy tester, but it's just a few resistors and a switch to switch between them. Easy substitution. You can unplug the wire to the gauge under the car where it branches to the fuel tank, or you can disconnect it at the bulkhead connector under the hood.

joe 06-25-2019 12:00 PM

There's an instrument/gauge trouble shooting section in the TSM. I'd start there. NOTE: "I'm electron impaired" so just guessing here but since your temp gauge is also inop I'd start testing there. There's a CVR (constant voltage regulator)built into the temp gauge that drops the voltage to the gauges. Don't remember the exac drop but it's down from 12v to 8-9v(?) or so. If that's fried I'd suspect no juice to the gauges. Haven't had that issue on a FSJ but have on a CJ where the CVR is built into the fuel gauge. At the time a new OEM gauge from the Chryco dealer solved my prob.
Did I mention I'm not an electrician but I'd start with testing input and output voltage at the CVR/temp gauge and work downstream?

tgreese 06-25-2019 12:21 PM

Both CJs and FSJs have the CVR in one of the gauges, in the fuel gauge and temperature gauge resp. Nominally the CVR makes 5 volts to run the gauges at that reduced voltage. If that's the problem, I'd suggest searching for threads here about replacing the Jeep CVR with a 7805 or 7806 integrated circuit. I've done this to my J20; pretty easy and it works great.

ShagWagon 06-25-2019 04:04 PM

Wiggle the connection ring on the back of the board. See if the gauge moves at all, and check the pins by touching them and making sure none have loose solder connections.

Bkgw 06-25-2019 07:41 PM

Ive played around with the main round plug on the back, Ill have to test the gauges in a few days to see if theyre dead or not. Everywhere I look in the engine bay I see cut wires, unplugged wires etc so who knows whats going on in the dash. Previous owner put in a retrosound stereo and may have messed something up to. When I replaced the fuse there was a 30 in where the 3 belongs!

ShagWagon 06-26-2019 08:10 AM

Pull out the instrument panel. Touch each pin to see if it

Pull out the instrument panel. Touch each pin to see if it’s loose. It’s common the solder breaks at the base of the pins. Trace the circuits and see if any are broken or corroded and that you are getting power through it. It’s not that hard to pull out. Replace all the bulbs while your there.


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