: Oil Pressure Sending Unit - SRX



jwatches
07-03-14, 08:01 PM
I want to use a conventional electronic Autometer oil pressure gauge on my 2005 SRX 4.6 Northstar engine. It has three wires; one for signal, one for low reference and one for 5V reference. If I use the signal wire, will it provide the correct signal for my Autometer gauge?

Submariner409
07-04-14, 09:33 AM
No. Our oil pressure switch is an on/off unit only, not a variable resistor driven by pressure change. (The SRX may be a bit different - consult a current circuit diagram for your oil pressure switch)

To use the AutoMeter or any other electric gauge requires a bit of trickery, hydraulic hose fabrication and brazing.

Buy a new AC Delco pressure switch, use it to find a proper sized brass piping T at a hardware store. Find a piece of brass strap about 1/8" thick. Do some measuring and have a piece of pressure hose fabricated, with male pipe thread ends.

The idea is to replace the sending unit in the oil filter adapter with one end of the hydraulic hose, braze and drill the strap to the T, drill the strap with mounting holes, mount and ground the T, install the AC Delco sending unit in one leg of the T, the AutoMeter unit in the other. Now figure out an attractive mount for the gauge. Wire it all up with proper ignition on power to the gauge and you will have pressure and the PCM controlled dash light/icon/messaging system.

Sounds complicated, but I have done it in Corvairs and 3 Taurus. Our engines follow the typical GM oil pressure thinking - 10 to 18 psi at hot idle, about 45 psi on the road. Remember: Oil flow is lubrication and cooling, not simply pressure.

jwatches
07-04-14, 12:00 PM
Thanks for the info. To be clear, this is a hot rod and since you mentioned it, a Corvair. See my site at www.jimsv8vair.net Anyway, I'm putting the LH2 mid-engine in my Corvair. I have the oil pressure sending unit from my old gen I engine and the wiring back to the guage. I just want to install the old sending unit to an oil passage or read off the stock Cadillac one. It sounds like I can't do the latter, so you are suggesting a way to build a "T" to use the same oil passage for both the stock and add-on sending unit, right? Are there any other oil passages I can easily access to drill and tap for the sending unit?

Submariner409
07-04-14, 01:29 PM
In a Northstar there's only one way to get to an oil passage to tap pressure: At the oil filter adapter.

Run the HD flex oil line from the filter adapter port to the brass T bolted to the body, and screw in the senders. Make sure the T is grounded to the engine with #10 wire. Good to go.

jwatches
07-24-14, 10:40 AM
I ended up finding a very easy solution for those interested. My engine is an 2005 SRX, so I am not sure how many engines this applies to. In my case, this is the LH2 engine used in the RWD and AWD models of SRX, STS and XLR. On the casting that the oil filter threads onto, there is a plug. I thought it was a pressure relief valave in case the oil filter gets clogged, but I found it was simply a plug with a standard pipe thread. I threaded in my Autometer sending unit and was done. I then found an identical plug on the water pump and was able to add the Autometer coolant temperature sending unit. Very clean and simple.