1979 D-100 225. Gauge inoperative. It's not the under vehicle ground wire. What should I check next? Thanks.

You'll have to acquire the wiring schematic and follow the wire from the tank to the gauge and see if its:

The lead wire
The guage itself
THe cluster has corrosion/breaks in the leads
The firewall plug if it goes through there

Good luck,

-D.Idiot

Is the engine temperature gauge also dead?

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Too many people who were born on third base actually believe they've hit a triple.

How do you check the gauge? It says in the FSM that the resistance should measure about 9 ohms when full. What does this do to the voltage that hits the signal input on the gauge as far a voltage goes. It also says in the FSM that 12 volts will kill the gauges.

Sam

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I use a 9 volt battery with a couple of jumper wires attached one to each pole of the gague, If the gague moves up you have ruled it out as the source. I am pretty sure I learned that right here.
Charlie

The temp. guage works. Also, any thoughts on the in-tank sending unit?

Whoops!! I misspelled GAUGE.

You can check the in tank sending unit. Put your ohm meter between the signal post and ground. Also, check the ground. PUt your ohm meter on the outlet tube, and a known good ground somewhere on the car. The bell should ring, or whatever audible signal your meter does. It should read 9 ohms when it is full of gas. Mine reads 10.

The reason I know this is that my gauge does not work either, and I have been trouble shooting it. My gauge is an auto meter after market gauge, which is advertized as 73-30 ohms, Ford/Chrysler style. The meter responds to ignition voltage by rising to the "E", but does not move above empty. My checks have determined that the sending unit is fine. My next check is to locate the dark blue wire in the body/harness plug behind the driver's side kick panel, and see if it shows 10 ohms between it and ground as well. If it does, then I will know the wiring is good through the passenger compartment. I don;t know how the signal wire is routed on a truck. It may enter through a bulkhead connector. I would be seriously tempted to run a new wire that by-passed that connection. But check it out first. As much as i dislike the bulkhead connectors on these old Mopars, they usually work OK for non critical connections. That is, connections where ae precise voltage does not have to be maintained.

Then, I may put a jumper wire from the blue wire to the feed post on the gauge. If this does not show a response, then I will know the gauge is bad. I suspect a wiring problem somewhere. But the last time I went through this kind of exercise with my Accel ECU, it turned out the wiring was fine, and the ECU was the problem. There is a chance that this meter needs some sort of interface unit, in spite of the fact that it is advertized as Mopar,Ford. I will give them a call soon. Good luck on yours.

Sam

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