Two Tiny Electrical Gremlins

[87MJTIM]

Why do you have to isolate the whole cluster? All you need to isolate is the voltmeter + sensing lead. For the HOs, it's easy; just locate and cut the sensing lead at it's PDC fuse and extend it over to the main PDC feed MAXI fuse, which is ignition switched. That way the VM sees pure charging voltage from the alt before it gets loaded down by all the branch circuits. 

 

Maybe it's tougher with the Renix system since they have no PDC, but by using the method it should be doable.

 

you are correct: no PDC in a Renix.

 

The whole cluster is powered by one wire (Wht/Blk) from the fuse panel.  I don't see a way to isolate the Volt meter from the other cluster gauges.

[HOrnbrod]

You're missing the point. The voltmeter does not use the "cluster" 12V power. It's a stand-alone independent gauge; pull it from the cluster and hook up a 9V battery to it's terminals (observing polarity of course) and it will indicate 9V if it's accurate. It has it's own sensing positive input wire that passes through the cluster harness connector, then goes into the engine harness where it terminates on the fuse block. You have to ID this wire, disco it from the fuse block where it connects to the "gauge" fuse, then re-terminate it upstream so it can sense charging voltage before the branch circuit devices that drag the charging voltage down. From the little I've seen with Renix vehicle schematics, it will probably ohmed out to find a suitable sensing point that is still a switched ignition point. The Renix era wiring diagrams I've seen just don't go into enough detail to isolate the voltmeter sensing lead. Maybe the regulation 88 FSM schematics will show this, I don't know. The Chrysler FSM's sure do.............

 

Anyhow, good luck, I'm done.   :thumbsup: