LS3 swap, new gauges install help
 

Hey guys, I just picked up New Vintage 69 series 3 in 1 gauges for my 69 Camaro LS3 swap project. The gauges call for 12V positive trigger to light up the built in warning lights. The parking brake is a negative trigger I'm sure and I believe the GMPP MIL (check engine light) indicator is as well. Can I use a Bosch type 30a relay to convert the polarity from neg trigger to pos12v trigger ??

Yes, that is a very common use for relays.

30 - 12V power, either constant (battery) or ignition switched depending on usage
87 - 12V power output to your gauges
86 - same 12V power that is connected to 30
85 - ground trigger such as your parking brake switch

No power flows until the parking brake is engaged at which time the parking brake switch grounds the relay coil causing it to trip and pass power out through terminal 87.

Thank you very much!! I was thinking the 30a relay was overkill for this application and that there would not be enough power to supply the warning light. (160 ma for the relay coil I think?)