Fuel/Temp Gauge problems

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imabigbangkindaguy

imabigbangkindaguy

10 Year 15 Year
Joined
Dec 2, 2009
Threads
48
Messages
532
Location
Ft Worth, TX
Hey All, I am having an issue with the two gauges. They will work fine on start up, but about 3-5 min into driving anywhere they will both slowly die at the same time. Occasionally I can see them fluxuating, both at the same time. When I am out running errands and taking the 40 on quick little trips, the two gauges will not work at all. If I go somewhere and let the 40 sit for an hour or so, the gauges will work at first, but then die after a few minutes of driving. I checked that both gauges are getting power, contacts are clean, both sending units are functional and less than 2 years old. My rig is a 76, 12 volt, Non-Californian FJ40.

What could it be???
 
I found a couple of different threads about this subject, however all were resolved with a simple cleaning of the contacts.

I wish it was as simple as a bad ground. But hey it still could be. Improper ground contancts (of my own laziness or stupidity) , were the bain of my teenage years, always followed up with a ghostly image of my father telling me to check all my connections before the job was done...

One thread said something about the fuel gauge having a volatge regulator?? I know that the Fuel and the temp gauge share the same power circuit, but why would they both fail in the drive? I dunno, somebody please help me out!
 
Check the wiring harness ground. It connects to the inside of the right frame rail beneath the gas tank. If I recall correctly, it's a white wire with a black line.

On top of that clean the fuse contacts.

Good luck:)
 
Checked the ground wire, and I cleaned the connection, even though it was nice and shiny, and still I am getting the same problem... Will work on start up then after a few minutes, just drops to nothing, any ideas??
 
OK, took out the gauge cluster and cleaned every contact point. They were pretty much already shiney to begin with, put the cluster back in, and the same thing.

WHERE SHOULD I LOOK NEXT??????????????????????????????????????????
 
imabigbangkindaguy said:
Hey All, I am having an issue with the two gauges. They will work fine on start up, but about 3-5 min into driving anywhere they will both slowly die at the same time. Occasionally I can see them fluxuating, both at the same time.
Click to expand...

I'd venture that you've got a broken wire (or worn wire insulation) that's gets hot an sags or deforms and breaks contact.

I once had a glass fuse that was burned out but worked when cold. Once the fuse got hot (bad internal connection) it would deform the interior metal strip and the fuse would act like it was bad. Whenever I stopped to test it the fuse would cool down and test out OK.

Are the gauges on the same fused circuit?
 
Hmm, interesting about the fuse, I will check that in the morning.

My understanding of the schematic and the circuit board, is Yes they are on the same fused circuit. so hopefully it will be that simple, and I just have one of those tricky fuses.
 
I think this is a problem to do with the vr or vl , voltage regulater or limmitter that is built in to keep them from fluctuating.
Do a search it has been posted before.
They do share the same positive feed , so the grounding comes from the sending unit per gauge so bad ground will not explain this problem. They are not getting the regulated V is more like it.
I don't fully understand it to give you a clear answer .
Try another cluster if you can find one intact and cheap.
 
Those are my thoughts as well. There seems to be and issue with the power consistantly getting to, or staying at the fuel gauge. Yeah, a new stock cluster or even stock cluster parts I think is out of the question. I will check the fuses later see if perhaphs there is a fauty or tricky fuse like Numby pointed out. May be time to get an aftermarket gauge cluster... I have really been drooling over the one Teletak, keeps saying "Coming Soon"

FJ40 DIGITAL INSTRUMENT PANEL - Teltek U.S.A INC.

But that is only if I cannot fix or source the problem of the stock gauge cluster.
 
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