As some of you know, I'm finishing up a CJ3A for my wife.  I got all the electrical done this weekend.  I drained the battery down pretty well while working out some lighting/grounding issues.  I was happy to see the ammeter start to function correctly after polarizing the generator/regulator.  When accelerating, the ammeter needle jumped to the positive which indicates the system is recharging the battery.  Excellent.  When I turned on my headlights, and only at an idle, the ammeter dropped to the negative.  Good.  Just what I hoped to see.

But then I noticed the oddest thing.  The fuel gauge was mimicking the ammeter.  For every movement on the ammeter needle, the fuel gauge needle did exactly the same thing.  I'm mystified.

Any ideas on what I did?  Or what may be going on?

This is a 12v reproduction ammeter and fuel gauge.  Pretty sure I hooked up the Walck's harness correctly.  Everything else works perfectly.

Hawk   

Hi Scout,

I did add an additional ground to the sending unit plate.  (Seen below)  The newer fuel gauges have 3 contact posts.  One for power (+), one for the sending unit (in the center marked 'S') and one for the ground (-).  There is no wire included for this 'ground' in the Walck's harness...and no reference to it in their instructions, but I added a ground wire on my green Willys (which works fine), so I added the same wire to this one. 

That's a good question Randy.  I don't know yet.  I haven't run it long enough to fully charge the battery.  There is about a 1/4 tank of fuel, but the fuel gauge doesn't drop much below 1/2 tank, but climbs to about 3/4 full as I accelerate.   Pretty much like the ammeter.

The fuel gauge is the type that you can fine tune with a small screw driver.  I haven't done this yet.  I guess I'll fill the tank,  try to eliminate the extra ground wire, and maybe disconnect and reconnect the feed wires to see if this 'shocks' it into reading accurately.  This is strange.

I keep thinking about this...Thinking out loud now...

Normally power goes to the gauge and then to the sender and then to ground...

Now you have power to the gauge, then power to the sender, and then ground directly back to the gauge....

Maybe grounding the gauge to the frame, and then the sender to the frame would break the loop?

At least now the faster you go the further you can go!

" but climbs to about 3/4 full as I accelerate."

I think there is a long description of how to test and adjust the voltage regulator in the manual...

I tried it once and gave up almost immediately..

There is a shop here that is supposed to be able to adjust regulators, but they wanted the generator too..

I found it easier and cheaper to buy a new regulator..

I suppose the sending unit is 12 volt or does that even matter?

My "Ford" kit car used a Motorcraft 12 volt alternator. The Smiths instruments I used were originals. They were "over ridden" by the mass voltage that they were not used to having. LOL, English  I had to install a resister to drop the voltage feed down so the gauges weren't pegged when I reved up the engine. Maybe this same idea would help your gauges. Oilly

Tim,

I remember having an issue with my new gauge as well. On the back of my gauge there were 3 connections. I purchased the gauge from KW and when I called them to see if they could help with my problem they told me to run a ground wire to the body from the back of the gauge. I believe I connected the center post to ground. Do you have 3 connection posts on your fuel gauge? If so this may be the culprit.

Just a thought here, you can pick up some pretty decent gauges at a reasonable price from most auto parts stores.  Replace the gauge you are struggling with just to see if this will eliminate the problem.  If the new gauge works right you will know if its a gage problem, if it goes wonky as well you will know its a sender/ wiring problem.  Might help you focus the problem solving.