fuel gauge problem

so i have made my 1953 chevy 12 volt and the fuel gauge reads full and have put a drop voltage on the gauge and still reads full.does any one any help in this matter cause im at a loss,i thought i have tried everything.please help.
thanks

 

Sounds like the sender side is grounded. Pull off the sender wire and test it with a test lite. It should glow and the guage will start to climb. Then try touching the sender wire to a known good ground, it should then go straight to full. If it doesn't react at all, check the wirte for continuity (breaks). If that checks out test the guage itself with a ohmeter, could be the guage is junk

 

thats the problem that it constantly reads full

 

Check with you're local parts store for ohm rating for you're car. Early chevys were I think 0-40 ohm. Later(early-mid 60's)gm switched to a 90ohm. figure out what yours is and run an ohm check. Usually it's just a loose connection, if not its most likely the sending unit. But in old cars you can never rule out the gauge, so start with one end and work towards the other.

 

your gauge uses a sender that has 0 ohms empty and 30 ohms full

 

I am using a boat sender to replace my stocker, $25. I don't know if voltage matters, since it uses resistance to figure?

 

I could'nt remember weather it was 30 or 40.

 

How are you dropping the voltage? If trying to use a resistor, that may be the problem. You might use a "chopper" like what came stock on Fords from about '57 until the '90s, or you can find a true constant voltage regulator (CVR) - I'm using one from Moser Electronics - it was about $.10 - yep, ten cents.

It absolutely matters because of ohm's law. If you keep your resistance the same, but double the voltage, the current will double and your gauge will read incorrectly...

 

You mean that it stays on full even with the key off? Wouldn't that indicate a faulty gauge?

 

sorry,the key is on and the gauge reads full


by the way thanks for everybody's help

 

I got the same problem,I hooked up gauge&sender before I put the tank in and every thing worked,after I put it in the car shows past full all the time,hadn't had time to work on it yet,only run out of gas one time.

 

Absolutely correct on the ohms law and your situation. You simply cannot put a dropping resistor in series with the fuel gauge unless you know the resistance of the coils in the gauge. Then you can use the ohms law formulas to calculate the proper resistance, and don't forget the wattage of the resistor too. That, along with the resistance of the sender will cause the gauge to do weird things.

I agree on getting a constant voltage regulator and wiring it in series with the gauge. This will at least solve the gauge voltage problem, the sender still would need to be addressed.

 

Naw, sender should be fine. Basically, you're isolating the system and running it on 6V (or 7.5V like most CVRs put out). The sending unit typically completes the circuit to ground via a potentiometer (variable resistor)...

Naturally, the sender must be matched to the gauge though...which is probably what you're saying!

 

The gauge has two terminals, which did you connect the (drop-voltage) resistor to?

 

i connected the drop voltage to the power terminal

 

Yes, this is what I meant, sender unit resistance must be matched to the gauge, but before doing this, make sure you do have 6-7volts at the gauge, no matter how you want to drop the voltage. I am pretty darn sure you will have more than that if you just use a dropping resistor type reducer, this is why a CVR is a better approach.

 

Get a 30 ohm sender, I went through this with mine using a boat sender.