The only problem you would have with installing a mechanical gauge, is that you need two - one for each side on the 239. You could use two of them and either mount one below the dash or both in the cluster and move the amps down below the dash - something like that.

But basically it's a matter of removing the innards from the stock electrical gauge, buying a new mechanical gauge - remove the new works from the new gauge and install them in the stock case.

The reason I asked if the other gauge worked before is I'm wondering if you have flip flopped your wires going into and out of your voltage reducer.

You see, if the power drops the needle down to "C" and has a mild short or the reducer stops working, it blows a fuse or the regulator shuts down, then the power shuts off and the needle will travel back up to "H."

So, check the fuse again too.