The Stovebolt Site Forums The Shop Area The Electrical Bay Fuel gauge problems

Have a '49 3100 6v. When a 30 ohm sending unit is installed, the needle on the gauge only moves about the width of the needle near the empty hash mark when the float arm is operated from stop to stop. When hooking up a 240 ohm unit, the needle operates accurately but in the opposite direction. Float up, needle down; float down, needle up. At the half way spot, needle reads half full. Gauge is original.

Can I switch the leads on the back of the gauge without damaging the gauge? Or, could I use a Ford product as I believe they are wired opposite from GM products. In other words, grounding the gauge wire at the sending unit will peg the gauge full on one make (can't remember which) but peg the gauge empty on the other make. Hope someone can help.

Dave

Don't switch the leads, it will fry the fuel gauge. When I hook my 30 OHM fuel gauge to a sending unit that is not matched for the gauge, a 78-10 OHM for example,the needle moves backward as you describe, that is why the two units need to be matched in OHMS. I have been troubleshooting my own gauge and discovered it was grounding its posts to the holes in the gauge bucket so be sure when you tighten the posts to the housing that they do not touch the bucket. http://s23.photobucket.com/user/littlebuddytoo/media/48Chevy/Bucket.jpg.html I had to put a tiny bit of shrink tube at the bottom of the post to keep it from touching the other metal. I would say, check and recheck your grounds also.

have not seen a Philips head on the back of a fuel gauge before?

That's because I put it there to keep the two halves together when I re soldered the coil
wires.

To littlebuddie and DADS50:

I finally came up with a solution to my gauge problem. The answer is a bit lengthy and didn't want to type everything twice, so I'll have you go over to forums.aaca.org/ to see the answer. When you get there, click on "Technical" and look for the thread titled "fuel gauge wackiness 1949 Chev 1/2 ton PU." My username is "davidyavidy." You'll see the answer there.

Again, thanks for all your input.
Dave

Ever heard of copy and paste? As much as I am interested in what you figured out, I am not interested enough to jump through all of your other site loops.
Carl

Was your 30 ohm sending unit new or old? Did you bench test it for functionality? Just curious. Let us know how the upside-down 240 ohm switcher-roo goes as your tank empties to see if the unit is registering correctly.

My 30 ohm sending unit was brand new out of the box (from Jim Carter I believe). Using a multimeter, I had 1 ohm on the low end and 33 ohms on the high end. After flipping the rheostat on the 240 ohm sending unit, I had readings right at the empty/full hash marks when the float rod was at the extreme ends of its travel. With sending unit installed, I had a full tank reading. I'll be surprised if I get anything other than an empty reading when the tank is empty.
Dave

Hearing about copy & paste and knowing how to use it are two different things for this dinosaur. Sorry for my lack of knowledge. However, another responder by the name of "tclederman" did insert a link to the other web site, so I clicked on it and it worked for me. Hope it works for you too.
Dave