Hi folks, could use some ideas. Two of my gauges either don't work or are flakey. The temp. gauge doesn't register anything unless you run the motor to get it up to operating temp. (180 degrees or so) AND then turn the engine off and restart the truck, then it sort of clicks over to the correct temp.

I bench tested the fuel gauge and it worked correctly, pegging to full with 3 volts of current.

I have not replaced any of the wiring but have either cleaned or replaced connections to everything and have replaced the fuel sending unit, previously.

So I am thinking the CVR unit, but haven't read anything that says when it fails the gauges simply don't work, although I have read the gauges will go kind of wild when these units are ready to fail. I should mention that the fuel gauge worked for a little while when I first got the truck but was never accurate.

It would be nice to replace the yard stick I use now to check the tank so any help is appreciated.

 

B9MZ-10804-C .. ICVR ~ Instrument Cluster Voltage Regulator (Motorcraft GR-508) / Obsolete ~ Available NOS & from auto parts stores.

Misc. applications: 1961/66 F100/1100 / 1965/66 Mustang / 1966/77 Bronco.

When the ICVR begins to fail, the needles of the fuel and temp gauges do the "hula" swing wildly back/forth on their own.

When the ICVR fails, these gauges no longer work.

The temp gauges on these trucks have never read correctly since day one. The usual reason why the fuel gauge doesn't work...is:

The float is made from two pieces of copper soldered together. Solder breaks down, gas seeps in, float settles to the bottom of the tank.

 

Thanks, the sending unit is new. I'll post once I discover the problem. I'd like to think it's the ICVR but the gauges never did the "hula" - they just stopped working.

 

Check the voltage coming from the regulator. It's a mechanical unit - a bimetallic spring is inside those little charmers. So it sort of averages the voltage down to around 5 or 6 volts, something like that, by ON/OFF every second or whatever. The gauges are slow to respond anyway, so this works. Lots of these VRs get replaced, when they work OK.

The TEMP gauge on these has always (apparently) been pretty vague from the factory. My 64 too, when I got it would barely crack 160 indicated, if that. Of course I "knew" it was a weak thermostat, hm, well then a voltage regulator problem. Then it "had" to be a sending unit problem. It will almost hit 180 now.

The fuel gauge is a different deal. Ground the sender hot wire at the tank and observe the gauge. It should peg FULL after a few seconds. That means the gauge and wiring are OK. If the sender is new you can easily calibrate sender and gauge indication by means of a set-screw securing the float arm to the sender. hope this helps.