[DufusDave]

I recently upgraded my gauges with some new "Auto Meter"; have found the gas gauge shows empty when I still have 5+ gallons left. (It's better than the old one which didn't work anyway.)
A little investigation showed me that the sending unit in the tank registers from 0-30 amps (pre 1965 style) while the gauge looks for 0-90 amps like newer vehicles.
Can I just add a resister in somewhere to compensate or do I have to look for a sending unit to match that will fit my tank? Has anyone else had this problem?

 

[roger1]

I recently upgraded my gauges with some new "Auto Meter"; have found the gas gauge shows empty when I still have 5+ gallons left. (It's better than the old one which didn't work anyway.)
A little investigation showed me that the sending unit in the tank registers from 0-30 amps (pre 1965 style) while the gauge looks for 0-90 amps like newer vehicles.
Can I just add a resister in somewhere to compensate or do I have to look for a sending unit to match that will fit my tank? Has anyone else had this problem?

First of all, resistance is measured in ohms not amps. But, we all knew what you meant.

No, you can't put a resistor in there to make it work. Autometer should have a 30 ohm gauge unless you have one of those combo units.

Otherwise, you are going to have to do something custom with your sending unit. They just don't make one that is 0-90 ohms.

 

[jwmbishop]

Depends on exactly what the roblem is. Three things - a mismatch as you found, tank shape, or bad sender.

0- anything is just that - so if a 0-30 guage and a 0-90 sender - you won't get it to match Did your investigation include actually reading the ohms at the guage end of the wire - or just getting the ratings form the parts descriptions? I would verify the ohms all the way through the curve before deciding what to do. this requires pulling the tank and mocking up each 1/4 of tank level (or starting at pump starve empty and reading every 1 gallon put back in to "see" the ohm curve - but then if you "discover the solution" you are left with a full tank at 6 some odd pounds per gallon to mitigate before pulling it)

Tank shape with a sender/float that does not match could have the float sitting on the middle of the tank bottom while there is still fuel at the low point - bad readings would be impossible to fix without pulling the tank and doing some bending of the float arm, by then a new sender to exactly match the guage would be in order.

A bad sender - as you noted it did not work before - a bad sender can go (for example) from 0-10 skip 10 -20 as a dead spot and then pick back up and read 20-90. Keep this in mind! This should be obvious when the guage seems acurate for most of the decrease then accelerates suddely to E.

I chose a dakota digital - the guage itself has a customizeable curve that I was able to match to my odd shaped tank - and related custom shaped float arm.

http://www.justgastanks.com/store/index.php?main_page=product_info&products_id=1353 0-90 sender

 

[mickym521]

I have the same gage and the same problem. I have checked the ohms, grounding, adjusted the float arm and adjusted how the stock tank fits. I got tired of pulling the tank and decided to live with it as is. I know that when the gage shows E that I have about 5 gallons left and the it is tme to stop and take a break.

 

[acardon]

A 0-90 gauge and a 0-30 sender should still show empty when the tank is empty. If you still have 5 gallons, the sender is indicateing zero ohms before the float gets to the bottom of the tank.
What Autometer gauge do you have?