78 volt / amp gauge question

[Mbeef61]

I just picked up a 78. Gauges all work but are really rough. Has volt gauge.

I found locally a really good shape cluster that is in much better shape but has amp gauge.

Can I just swap my volt gauge into this better cluster? Am I missing something?

I know there is more to it going from amp to volt and have read up on that, but since I am already volt is it as simple as just swapping my working volt gauge in place of the amp gauge on the better cluster? Anything different in the circuit behind the gauge face?

[ray_mcavoy]

Unfortunately, it's not quite that simple.

The switch from ammeters to voltmeters resulted in some changes to the printed circuit on the back of the cluster. I don't think the studs on the back of a voltmeter will even connect to the correct clips if you simply stick a voltmeter in place of an ammeter.

Also, your 78 will have an electric oil pressure gauge. The 73-75 clusters (years that originally had ammeters) all have mechanical oil pressure gauges. That makes for even more differences in the cluster pin-out and printed circuit on the back.

I think there are places that sell gauge face decals you could use to restore the appearance of your existing working gauges.

Or you could swap in a later year gauge cluster ... up through 87 plug in the same (gauges, not idiot lights). I think 88 & 89 R/V series clusters plug in the same too (90-91 are different because of electric speedometers though). Needles & fonts look different on 80+ but the electrical pin-out stayed the same. I think the temperature sending unit has a different resistance curve on 79 or 80+ so that would need to be changed.