Fuel gauge not reading properly

If the cluster or the sending unit's body (removed) ever (even momentarily) lose ground while it's internals is connected to 12 volts, normal connections while the key is turned to the "on" position, the "CVR" or constant voltage regulator will short out or fry.

The CVR is a small device built into the fuel gauge which works reduces the voltage from 12 volts down to approximately 5 volts to operate the fuel and the temperature gauge.

The original Stewart- Warner gauges seemed to be more bullet proof than the newer replacements.

This reduction is achieved through tiny fingers lifting up and down off of the 12 volt system, much like an old Ford's voltage regulator for an alternator. The 5 volts is transferred via the heavy jumper bar between the two gauges.

I found this to be the weakest part of the fuel/ temperature gauge system. Even a little moisture can destroy the CVR, with a CJ, that's not hard to come by!

So many folks consider both of these gauges as being in non-working order to be a "given" with a CJ.

After lots of thought and experimentation and frying many gauges I found a reasonable solution to the 5 volts required to operate both gauges!

Resurrection of the old fried fuel gauge will not usually happen. Sometimes the temperature gauge is still usable.

Now in more modern times the temp and fuel gauges are still sold in pairs.

I have found that my solution to this problem is to install the new gauges into the cluster but not using the traditional 12 volt connector to power the CVR.

Instead, "that" 12 volt connection will power the new 5 volt solution which will power the gauges.

This time, "my" 5 volts will back-feed the gauges and the original built in CVR will not even be used at all!

So the biggies in my system are:

Where the terminal on the gauge says "Not Used", that wire will now power the cigarette lighter inner terminal (which will power the USB adapter).

In the end, I taped the cigarette lighter holder and USB adapter together and they now reside in the dash behind/ near the cluster.

The only glitch between the original way and my way is the needle response is a little slower (but not real slow!) When powered up. On the up side, the needles do not seem to bounce or fluctuate as they did originally.

Any questions?

I hope this helps you out, especially my pics!

There's nothing like spending money on several sets of gauges and still having negative results when everything seems to work against you!

Keep us posted with progress!

The Medic

Sometimes I get carried away knowing what I meant, but leaving others still in the dark!

My 1st line in my response should have been:

If the whole cluster or the gauge within it is removed ever (even momentarily) and "ground" is lost ground while it's internals are still connected to "live" 12 volts, while normal connections are still intact while the key is turned to the "on" position, the "CVR" or constant voltage regulator will short out or fry.

What I've seen the most of is the whole cluster being removed while power is still hooked to it.

Pic 2 is tests you can do to check things out.

Let us know how it's going.

The Medic