1939 Dodge D11 gas guage inop

[Guest Mark in FL]

I am having an issue with this 1939 Dodge D11 Business Coupe. Fuel tank rusted through. Tanking sending unit was shot. Open circuit. This sender uses two inputs. Purchased new sender from Andy Burnbaum. Sender works as it should 0-35 ohms on one pin and 35-0 ohms on the other. Removed gas gauge from dash and connected units together with new wires. Making sure to connect properly as this a positive ground vehicle. #1 terminal on gauge to #1 terminal on sender, etc. Sender and gauge both grounded properly. Gauge would only read empty or full. Nothing in between. I cleaned gauge contacts which are part of the works on the front side to no avail and also tried the calibration procedure I found in a 1939 Plymouth workshop manual I found online which matches the vehicle I am working on. Same issue. I ordered an NOS gas gauge from Andy Burnbaum. Matches exactly. Connected as before with same results. Connected in vehicle with same results. I am a tech of 40+ years and this isn't rocket science but this has me baffled. Any help would be appreciated. Thanks

[JACK M]

On my 47 Chrysler I had the same results on the bench.

But it works in the car with real gasoline.

Go figure.

[garyp1]

I also have a 39 business coupe are you doing a restoration on it?

[Kevin bc]

Hi guys

For what it is worth. My gauge was very frustrating for a long time. I'm also a tech of 40+ years, and it baffled me for 6 months or more I reckon

Don't know if your gauge is the same as my 1930 DC with 2 coils , but if it is then when you have the gauge out of the car bench testing it then the case of the gauge has to be earthed to the power supply, as the second coil is hooked up to earth or the case of the gauge, and if you just connect to the terminals on the gauge then the 2nd coil is open circuit, (which if I remember correctly gives you either F or E) so you would also have to make sure the gauge is well earthed when in the car.??. You can see my type of gauge in a Dykes manual on page 652 AC type. Another thing I found was that the tank from full to empty did not use the whole range of resistance, mine being up to 130ohms, ,and I could get it to work out of the tank but not in the tank. it was either F or E. After a lot of cog adjusting I have been able to find a medium using about 50ohms where Empty is Empty, and  a 1/2 F tank is around the middle & the F reading is ??? which I guess does not have to be real accurate. E is the critical factor

Good luck

regards

 

Kevin BC

[Guest Mark in FL]

Thanks guys for the responses. Sorry to be so tardy. Just received a couple of comments and got my computer back up after Hurricane Matthew. I took Jack M's advice and tried the sender in the tank with gasoline since it didn't work properly on the bench and I could find no issues with it. Seemed to work great. The car has since been traded off by my boss/owner of the Mazda dealership I have worked at for nearly 40 years. He traded the '39 Dodge Business Coupe (a nice car which may have been nearly all original), a '49 Military Jeep which was in incredibly great shape, a 1921 Dodge Brothers 4 door convertible (another great car with very interesting mechanicals, like the "silent starter" which used the huge generator to crank the engine) and a 1968 cloned Hemi Charger and some cash for a gorgeous 1929 Packard 626 Speedster Runabout. This car was a Pebble Beach Concours car. Thanks again!