Armchair electrical engineers: tank gauge readings

[patrickdotryan]

Hi guys. I read the gas gauge tech article, which is awesome. But with my multimeter I want to check my readings. They look way off. Can someone please help? The tech guide says at full I should be getting 8-12 ohms at full and 70-73 ohms at empty. I show .051 at full and .114 at empty. I am using the same multimeter scale setting as shown in the article (2k). Is my gauge faulty or is it my brain? Patrick

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[HIO Silver]

The difference between your readings looks about right.

Try a lower setting for more accuracy.

[patrickdotryan]

Thanks HIO. Just tried it on the most accurate setting and got close to the same results with the decimal point shifted.

About 40-50 when full and about 110 when empty. That seems different from the tech article range of 10-12 full and 60-73 empty.

My symptom is when the tank is full it only shows just over 1/2.

Thoughts?

[fijidad]

Thanks HIO. Just tried it on the most accurate setting and got close to the same results with the decimal point shifted.

About 40-50 when full and about 110 when empty. That seems different from the tech article range of 10-12 full and 60-73 empty.

My symptom is when the tank is full it only shows just over 1/2.

Thoughts?

Interesting...I have the same issue on my '71 F250...tank full & reads about 1/2 full. Occurs on both tanks. I haven't tried to fix it, but will be interested in what comes from your post. Regards, Dan

[patrickdotryan]

Anyone else have any ideas? Dan, I pulled the little sender unit apart and cleaned it but it all looked good in there. The little contact was tracking on the curved coil exactly where it looked like it should be.

All I can surmise from my readings is that if the tech article is correct and if say 10 is full and 70 is empty, my full reading of 40 is somewhere in between that so maybe it explains why at full I only show half a tank.

But I'm guessing. Might be a few weeks before I get it back and powered up to see if the cleaning did anything but I suspect not.

Patrick

[1972hiboy]

I think your going to de dealing with a fine balance of adjusting the IPVR and the guage itself to abtain the correct reading. There is a really good thread on this but I have to find it. So your guage reads only half full with a full tank. at half a tank does it read empty on the guage or does the guage accuratly go to empty when the tank is really empty?

Edit, found it. not sure if this is the article you were reading but this has aot of good infor in it.

http://fordification.com/forum/viewtopi ... fuel+guage

[HIO Silver]

Ever take an old the sender apart?

The resistive wiring is "wound" (hence, "windings") around a non-conductive bar and the float arms wipes its brush along the windings to correspond with the fuel level.

Over time, the windings can get bunched up at the bottom with no or few windings near the top. On my Mustang the first 1/2 tank indicated drops real fast and then slows down because the windings are so tightly bunched together.

[patrickdotryan]

Thanks HIO. I did actually take it apart and (unfortunately?) the windings looked really good and well spaced out. The little contact that rides along the coil looked good too. I couldn't see anything physically wrong the the internals of the sender. The readings still don't look right to me, but that is from a sample of exactly one! Patrick

[patrickdotryan]

Also thanks Highboy. I haven't had a look at the actual dash gauge because I'm pretty sure that the temperature gauge has always read correctly. If I recall, adjusting the mechanical part of the gauges, all gauges go up, so my tank may read full, but then my temperature will look too hot. I guess I can wait until everything is back and running with the rebuilt motor to see about the temperature. I have a new water temp sending unit and my cooling should be all good so I'll have a good baseline.

Cheers,
Patrick