Automotive Relay Question

[turbojimmy]

Hi all,

My daily driver is an '01 Cadillac DTS. When you turn on the fog lights, the DRLs (reduced intensity headlights) stay on. Lots of folks just pull the fuse and eliminate the DRLs. Being the geek that I am, however, I would like something a little more sophisticated.

The fog lights and DRLs are controlled by the Dash Integration Module which is one of 3 body control modules in the car. I've identified the wires that complete both the fog and the DRL circuits. Because they are controlled by the computer the feeds are very small (probably 18 or even 20 gauge wire) and they run to micro relays under the hood. I figured what I'd do is get a normally closed micro relay to interrupt the DRL circuit when the fog lights turn on. Trouble is, the only relays I could find are a teency weency (and I mean SMALL) 12V circuit-board mountable relay and a heavy-duty fan-motor relay. Both are normally closed. The big fan relay would be easiset to install - you think the resistance of the coil will bake my computer? I think that this will load the entire circuit including the circuit board in the computer but I'm not sure.

Thanks,
Jim

 

[NJVetteGuy]

Hit a local electronics store, many relays have 1 NO and 1 NC contact. Since you're only interrupting the coil voltage to the other relay, you only need a relay rated for maybe 1-2 amps at the most.

 

[turbojimmy]

Hit a local electronics store, many relays have 1 NO and 1 NC contact. Since you're only interrupting the coil voltage to the other relay, you only need a relay rated for maybe 1-2 amps at the most.

I think I blew the $10 for the big relay for nothing then. I tried the local Radio Shack and they didn't have any NC/NO relays, at least not automotive type (they had PCB mount relays). I did find an online source for the factory relays (manufactured by Omron) that has an NC/NO relay that is the same size as what GM installed in the car. It's only $4.98. I might go that route.

Thanks,
Jim