Voltmeter installation on 88 924s

[matt1415]

I want to replace my clock with one of the factory voltmeters out of the cars that were not optioned for AC. I want to know if you guys have any suggestions on what to do with the wiring. I know the easiest way would be to wire it in series with the oil pressure gauge but my concern is this would only show me the system voltage and not direct voltage from the battery. Unfortunately both the clock and cigarette lighter run constant with ignition off which is a shame as they also both use direct power from the battery. I don't want to have to splice into the ignition switch or run any new wires directly off the battery/alternator. I would like to try and utilize what I already have at the centre console to power the voltmeter with ignition on.

[TheSecondChris]

Cool idea about adding that gauge in place of your clock. Does your clock not work or do you just want a volt gauge instead?

Another option would be to use the wiring for the radio since there is a wire for switched power that you could use, however the oil gauge should also show you battery voltage as I don't think it has a different system voltage. I'm surprised the cigarette lighter is not switched - I'll need to check that on my car.

[murrayg]

I wired mine into the cig lighter. It is not switched, so it always displays battery voltage. It draws essentially no current, so it doesn't drain the battery if the car sits for extended periods.

Gord.

[matt1415]

Originally Posted by TheSecondChris

Cool idea about adding that gauge in place of your clock. Does your clock not work or do you just want a volt gauge instead?

Another option would be to use the wiring for the radio since there is a wire for switched power that you could use, however the oil gauge should also show you battery voltage as I don't think it has a different system voltage. I'm surprised the cigarette lighter is not switched - I'll need to check that on my car.

Clock actually works fine but between the nav and the radio I could do with something a bit more useful to me.

[smokin_944]

Just curious Gord, where did you source out the volt gauge? Is it similar to the Porsche gauge? I also have an early car and would like to ensure that it fits the console in the same place as yours...

[onZedge]

I replaced my factory clock with a VDO Voltmeter.
According to the factory wiring diagrams, the Oil Pressure Gauge and Voltmeter use the same switched +12VDC wire. Circuit 15 (switched by ignition), black wire. Use the brown ground that originally went to the clock.
I also put a digital voltmeter directly on the battery and adjusted the new in-dash voltmeter to match.

[matt1415]

Originally Posted by onZedge

I replaced my factory clock with a VDO Voltmeter.
According to the factory wiring diagrams, the Oil Pressure Gauge and Voltmeter use the same switched +12VDC wire. Circuit 15 (switched by ignition), black wire. Use the brown ground that originally went to the clock.
I also put a digital voltmeter directly on the battery and adjusted the new in-dash voltmeter to match.

Thanks for the clarification on the wiring. How easy is it to calibrate the voltmeter?

[onZedge]

IIRC there was a hole in the side of the gauge case that allows access to the adjustment potentiometer screw.

[ecostellodo]

I found one at a Porsche dismantler