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bradnree
12-29-2006, 10:34 PM
When I use a test light on the wire in the trunk, in the gas tank sending unit access hole, the shining light is really just a red glow not a full bright light. Is this normal ??. The gas gauge does nothing when I hook it up and move the sending unit "arm". What's the fix ??........Brad

Rosstude
12-29-2006, 11:04 PM
The sender varies the resistance to ground, your test light will tell you nothing. If you have a multimeter, you can use it, on the Ohms scale, to check resistance of the sender as you move it. Also use the multimeter on DC voltage to check if there is voltage (6volt?) at the gauge head, you could use your light for this. The gauge has 2 wire connections, 1 voltage -on with key, and 1 to the sending unit.
So, when testing with the sending unit out, one must ground the sender well, in addition to leaving the wire hooked up. You can also remove the wire from the sender (make sure it isn’t touching ground), and turn the key on which powers up the gauge, and then touch the wire back at the sender to ground, the gauge should go to Full when the wire is grounded, and to empty when not grounded. Do not leave the wire at the sender grounded for too long, or leave the key on too long, just to be safe.
Hope this helps

[img=left]http://i52.photobucket.com/albums/g27/Rosstude/11-27-061.jpg[/img=left]
Ross.
Riverside, Ca.
1957 Provincial X2
1958 Transtar

bradnree
12-30-2006, 01:25 PM
I tried a multimeter on ohms, the numbers on it don't settle down and constantly change. I tried several hookups and grounding. None of the dash gauges "jump" when I turn on the key...............Brad

Rosstude
12-31-2006, 12:40 AM
You may want to start on the instrument panel, checking for voltage. If your meter is digital, they can seem “jumpy” compared to an analog.

[img=left]http://i52.photobucket.com/albums/g27/Rosstude/11-27-061.jpg[/img=left]
Ross.
Riverside, Ca.
1957 Provincial X2
1958 Transtar

gordr
12-31-2006, 02:55 AM
quote:Originally posted by bradnree

I tried a multimeter on ohms, the numbers on it don't settle down and constantly change. I tried several hookups and grounding. None of the dash gauges "jump" when I turn on the key...............Brad


Brad, make sure you aren't using your multimeter's ohms function when the gage circuit is powered up, meters can get fried that way.

Also, disconnect the wire (orange, IIRC) from the sending unit before trying to measure the resistance of the sending unit, and then measure from the sending unit terminal to the round disc of the sending unit top. Clean off rust in a spot first.

The best field test for a gas gage problem is like Ross suggested; turn on the ignition, and connect a good ground to the sending unit wire for a few seconds. If the gage goes up to Full, and beyond, then the gage itself is probably good.

If the gage passes that easy test, then you have one of the following problems: bad sending unit, bad grounding of the sending unit to the fuel tank, or bad grounding of the tank itself to the frame. The sending unit HAS TO "see" a ground in order to work! It could not hurt to make up a short wire with a ring terminal on each end, and put one end under the head of one of the sending unit mounting screws, and the other under a sheet metal screw into a clean hunk of body metal somewhere handy. I had to do exactly that on my old Suburban.

If the gage still refuses to work with a good ground to the sending unit, then it is time to remove the sending unit. That's the best time to check it with an ohmmeter, as you can move the float arm through its range, and watch for points where the ohmmeter jumps to "infinity". I really prefer an analog meter for this chore; digitals are lousy for monitoring trends in anything.

I have seen sending units where the rivet joining the external terminal to its internal counterpart has corroded away.

Gord Richmond, within Weasel range of the Alberta Badlands

bradnree
12-31-2006, 08:40 AM
getting an analog meter this a.m., good bye digital......Brad

bradnree
12-31-2006, 02:29 PM
I bought an analog multimeter and performed the above tests, both the gauge and sending unit work...Thanks...Brad