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philbirkeland
05-06-2010, 11:41 PM
I have converted my 2R10 pickup from 6V positive ground to 12V negative ground. I am considering either an Autogage or VDO gage set, to include a fuel gage. Both companies sell fuel gages to match a number of different fuel level senders, as to resistance empty and full.

The thought came that I might be able to reuse my existing sending unit, even though it is designed for 6V positive ground. All the gage sees is two terminals with a variable resistor (potentiometer) connected between them. The gage doesn't know polarity or voltage, only resistance. I can't get the sender out to measure the empty and full resistances, because the floor access hole is about 2" offset from the sender flange. To get the sender out, I either need to drain and drop the tank (ugh!) or take a nibbler to the floor panel (not very neat and shipshape, so also ugh!). Access to the two electrical terminals for the gage wiring is good, even through the offset holes, so I don't need to get the sender out for wiring up the gage.

In theory I could drain the tank to measure the potentiometer resistance empty and then fill the tank to measure the resistance full (a lot of work!). If somebody out there already knows the resistances full and empty, my job gets much easier! If you know the resistances, please post them. I will be most grateful.

Best, Phil.

Philip W Birkeland
1950 Studebaker 2R10
<jeanbirkeland@mac.com>
253.564.9109 h
253.279.9724 c

gordr
05-07-2010, 09:26 AM
Phil, you have the old-style two-terminal sending unit. Practically all modern dash gauges are "single-ended." Your sending unit is a potentiometer with the wiper grounded, and the two ends connected to the works in the gauge unit. So the resistance on one side increases as it lowers on the other side, with movement of the float. Modern sending units are "single-ended"; they have a resistance element with a grounded wiper, and it's resistance simply lowers as the float rises.

Now you might be able to use simply one end of the current sending unit, but I don't know if its resistance range compares even to that of the later single-terminal six volt sending units.

If you are going twelve volts anyway, I'd say drop the tank, and install a new sending unit compatible with the gauge you plan to use. Chances are the old sending unit is about worn out, anyway, and if it worked at all, it would be inaccurate. Gives you a chance to inspect the interior of the tank, and clean it if necessary, and to clean and paint those areas above and beside the tank that can't otherwise be reached. Do save the old sending unit, because somebody else may need it.


Gord Richmond, within Weasel range of the Alberta Badlands