Hello,I'm installing a Volt meter in my 71 cutlass S with 350.My question is do I go from Horn relay to gauge and other side of gauge to Battery?.What about the idiot light.Thanks for any help.Tom

 

For the voltmeter source you want to choose any keyed on/off 12v source. If you use a constant source like the horn relay the meter will read 24h/7d a week and drain your battery when not in use. The ground side of the gauge can be any metal body part since the whole chasis is grounded to the battery.

The backlighting will need to be spliced into you headlight/gauges circuit so the are only lit when the light are on. Other will chime in on the wire locations.

Adam

 

^^ Pretty much that's it.

Do you have wiring diagrams for your car? They will help a lot.

I like splicing by cutting the wire entirely. stripping the sheet, then twisting the two wires together ( car's wire and new gauge wire) on one side and just the car wire on the other side of a 22-18 butt conector. Hasn't failed my yet (going on 10 years now)

 

Soldered preferably...