VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Gas Gauge Issue

Hey All,
I have a strange issue with my gauge, I get a correct reading however it is only for a second or two as I turn my ignition key off. When the key is on I get no reading, when the key is off, again no reading. I know the terminals are correct I just don't understand why I only get a reading for a split second. Anyone have a similar problem?

Thanks,
-Davis38

Sounds like a loose wire issue. Start at the back of the gas gauge and with the iginition on, there should be 6V in and 6V out of the gauge. Then go to the tank variable resistor and see that you have 6V in. Somewhere along the line you are loosing your connection.

If you don't hold 6V at the gauge check the connection at the iginition switch. All this is assuming a stock wiring system.

Good Luck,
Brian

Yeah, I must be having the same problem...Loose wire...Thanks for the key switch idea...Would be the LAST place I'd look...Now, it was about six months ago I changed out the sending unit...Including a new/extra ground wire...And I'm sure I couldn't have "fouled" that operation up...BUT, my key switch was dangling below the dash for a while, while I was installing new choke and throttle cables...SO...Thanks, for your guidance...Kevin

If you still have a problem try this site.

http://www.fifthaveinternetgarage.com/tech_tips/tech_tips_gas_gauge.html

Thanks, Keith...That a great tech tip article...I'll post on what it is I found...When I find it...It's starting to bother me, this "reads one second"...Goes "dead" the next, then back on...Then off. I have to take my eyes off the road for to long to see how much fuel I have...lol

Sounds like a bad (intermitant)electrical connection, may even be at the sender unit in the tank especially if it occurs at or about the lower level of fuel. Try wriggling the wiring harness between the ignition switch and the tank while someone is watching the guage.

Tony

Hello,
my Gauge Needle is shacking all the Time. Can that be a Ground / Mass Problem too? The Sending Unit is new.

A float member floats in the tank on the fuel. This actuates a lever moving a contact over a rheostat. Two coils in the dash unit work an armature attached to the indicating needle. The position of the needle varies according to the current flowing through the coils and this, in turn, is regulated by the float controlled reheostat. All steel parts of the tank unit are cadmium plated. The rheostat or resistance coil is chromel wire wound on a celeron core and the remaining parts are brass, thus making the entire assembly completely rust proff. The outer terminal of the dash unit marked "ignition" is connected by a wire to the ignition switch so that the gasoline gauge is operated only when the ignition is turned "on". The center terminal, marked "tank" is connected by a single wire to the terminal on the tank unit. THE RETURN CIRCUIT IS THROUGH A GROUND AS BOTH THE DASH UNIT AND TANK UNIT ARE GROUNDED IN THEIR RESPECTIVE LOCATIONS. When the gasoline tank is empty, the floats are at their lowest position and the rheostat or resistance in the tank unit is completely CUT OUT, which results in one of the coils in the dash unit being completely "shorted" out and the other coil attracts the armature and the indicator points to "empty". As fuel is added in the gasoline tank the float raises and resistance is continually added to the circuit of one coil, causing it to become weaker; and the resistance is gradually cut out of the other coil, making it stronger, hence, the indicator will move in exactly the same ratio toward "full" on the gauge. The same action is reversed as fuel is consumed. Owing to the design of the gasoline gauge, current consumption is very low, between 1/16 to 1/10 ampere. Repair as follows. Pointer will not move...break in line between dash unit and ignition switch. Gauge shows "empty" all the time (moves slightly when ingition switch "on".) break in line between dash unit and tank unit. Shows full all conditions. Break in line between dash unit and tank unit. Note: The return circuit is through a ground as both unt dash unit and tank unit are grounded in their respective locations....make sure the tank unit has a return ground as you just replaced it. Note: High Restandce "open line" is a wire that is broken but has no indication on the outside (good insulation can fool you). Found by pulling on the wire a section at a time and see if it breaks apart. Good luck and double check your grounds.

Exactly...But, what's ticking me off is I replaced the old sending unit and added a ground at the tank...This is what I get for my trouble...! You know, the car had sat for so long...I think I had this problem before I started this project...And that's why I changed sending units and added a ground...I guess I just hadn't found the what I thought was the problem after all...Checking the key switch and gauge are next...

Thanks for all the help, guys...I think it's important to talk about the problem before just "diving-in"...We get a better understanding of the problem we're trying to tackle...Kevin

Ground...
seems most gas gauge issues are a bad ground.
Ground the sender and the gauge.. that may fix it!

Just out taking the '48 for a "spin" and remembered about the possibility that my "problem" could be a loose wire on back of the key switch...So, I reach under the dash and just touched the wires to the key switch and that's it...! I watched the gas gauge fly all over the place...Problem solved, loose wire to the key switch...Thanks Guys...Kevin