time delay switch for OBA

Has anyone wired any 12v add-ons with a time delay module/relay? I want to add an OBA setup but I don't want to add another switch on the dash. I was hoping to wire it so that the compressor will turn on only AFTER the truck is running...in cases that the air tank leaks down after sitting a while.

 

Bueller.....Bueller....

 

Maybe do something as simple as a relay setup triggered off the accessory or ignition lines. How many amps are you pulling? Most auto relays are 30 amps, but you can set them up in parallel, or find a higher amp, 100% duty cycle winch relay if the amperage is high.

https://www.google.com/search?q=auto+relay+setup

 

it needs to be on a delay. if not it will trigger on as soon as the truck is starting and it will put a lot of load on the electrical system...which is what im tryng to avoid. ive seen some digital delay modules but was hoping for maybe an inline resistor setup

 

Maybe hook it in to the neutral safety switch. If wired properly, it will only activate when the truck is put in drive (I'm assuming here that it has a traditional style NSS).