The following is a resend and credited to Bill Hanlon:
Hope it helps---The ground is an important element ......
You can't use the volt/ohm meter to verify the gauge, but you can use
it to verify the sending unit.
1. Disconnect the wire from the terminal on the tank's sending unit.
2. Connect the meter between the terminal on the tank's sending
unit and a GOOD ground (clean with a little sandpaper) on the tank.
3. Set the meter to a low ohms scale. The TF trucks read around 30
ohms when "full" and near zero ohms empty. If the reading is wrong
fix or replace the sending unit. In mine, the brass strap that
connected the actual variable resistor at the bottom of the sending
unit to the terminal on the outside of the sending unit was broken
and was easily repaired with 100 watt soldering gun.
If step 3 checks out good, you can figure out where the wiring is going
wrong by making a test rig that consists of a length of 18 gauge wire
attached to an alligator clip on one side of a 15 ohm resistor with
another length of wire attached to a sharp pointed device (I used a
large paper clip and ground a point on it). Exactly 15 ohms is not
important, 10 to 20 will do.
4. Disconnect the gas gauge wire where it attaches to the tank.
5. Hook the alligator clip to a good ground in the truck.
6. Turn on the key, but you shouldn't have to start the engine.
7. Touch the pointed end of the test rig to the gas gauge terminal
that goes to the gas tank. If the gauge reads still reads
full, the problem is in the gauge, the grounding of the gauge
or the power circuit supplying the gauge. If the gauge reads
around half full (or half empty if you are a pessimist) continue
probing the gas gauge wire as it makes it's way towards the tank.
When you reach a point that the gauge no longer reads half full
as you probe the wire you have gone past the open (break) in
the wire.
At 06:39 PM 7/8/99 -0700, you wrote:
>One final cry for help before throwing in the towel. I'm on my 5th gas
>gauge, and just unpacked my second sending unit from Chevy Duty. So far
>nothing close to working gas gauge.
>
>Question on the sending unit:
>
>How can I tell if the sending unit is working? When I hook up the ohm
>meter, with one lead to the terminal and one to the sending unit for a
>ground, I get an indication of continuity, but there is no variation when I
>move the float up and down. This is the same thing that happened with the
>previous sending unit, that I thought was bad. Is there a way to hook it up
>so that when I move the float up and down, the ohm meter will correspond?
>
>Question on the gauge:
>
>My ohm meter shows continuity from one post to the other. Does this mean
>the gauge is good? Before I buy yet another gauge, can I hook up my new
>sending unit to another gauge, and somehow see if it is going to work once
>it's installed in the truck?
>
>Thanks!
>
>Smokey
>'50 3600 5-window (The one with the gas can in the back)
>
>oletrucks is devoted to Chevy and GM trucks built between 1941 and 1959
>
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