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Old February 25th, 2019, 05:14 PM
WE7X WE7X is offline
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Join Date: Sep 2013
Location: Issaquah, Washington
Truck: 1970 GMC RM-7500 based Motorhome
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Default Re: What did you do for your GMC today?

I have not had one out of a P/U for many years, ( Mine are HD industrial aftermarket tanks on the RM7500 chassis, but as I recall there are two small tabs that the float arm bump up against at the upper and lower limits of the travel.
With the sender out of the tank, it should be possible to move the arm through the range of travel, to be sure you are getting the full resistance of the expected range ( 0 to 30 ohms; or 15 to 90 ohms) as specified for the correct sender.
If you are getting the correct range of ohms readings then the gauge may be the problem, but usually it is the sender that causes trouble.
Tank senders that have sat unused for a long time, can sometimes develop an open circuit. I saw one case many years ago, where a sender was 'dead' between about 1/4 and 1/2 tank. The gauge would work normally down to about a half tank, then suddenly go to 'E' for a while, then return to reading correctly for the last 1/4 tank.
It was a bit disconcerting when you suddenly saw it registering empty; and had to mentally stop and think if it was a true reading or just the dead spot.
Rod J
Issaquah, WA.
1970 RM-7500
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