View Full Version : Use for Stock Oil Pressure Switch

10-30-2009, 02:45 PM
AKA: Engine on detector

This came out of my quest to get the IC fan to only come on only KOER and not KOEO too, without a toggle switch.

I have a Autometer Oil Pressure gague so I had to add the factory switch back in and used BWD S4110 switch from Oreilly's (noted as being for "with gague"), has the plastic cap on it. Do not use the S103 for the "light" it will not work. Easier way to know is it the slightly more expensive ~$1. Advance does not have the in shelf stock and Autozone's are junk.

For only OEM MN-12 switch.

The pressure switch is a simple NO (normally open) switch and once pressure exceeds 7PSI it closes and completes path to ground.
That being so there are a couple ways to wire it I chose to use a relay since I already had on in place but is not necessary. Most basic setup is to get your 12V straight form the battery and apply ground to the pressure switch.
The better way IMO is to pull power form the ignition circuit after the fuse in the Power Distribution Box (BK/O) to drive the relay coil (85) then connect 86 to the pressure switch. 87 connect to supply (batter) and connect 30 to 12v in on the fan.

Running pressure sensor (Autometer or the modded one).

All wiring is the same just need a 1/4"NPT TEE, with a male end or close nipple connecting TEE and factory fitting. Connect sending unit (not switch) in line with the Male end and pressure switch to 90* to both of them.

I'm using it drive the IC fan but the uses are endless for anything you want to have come on only with engine.