When I put the new motor in my car I add an autometer oil pressure gauge and coolant temp gauge. The temp gauge I was able to usethe supplied sender for. However I can not do that with the oil gauge. My motor only has one oil port, on the top under the distributor. That is occupied by the oil pressure switch needed to run my fuel pump.What I did was cut the wire for the stock gauge where it plugs into the oil pressure switch and connect the new wire for my autometer gauge to there. The problem I have is that with key on the gauge pegs all the way to 100. With the motor running it reads 75 but im not 100% sure its reading right. I dont think it should peg to 100 with key on. What did I do wrong? Any help as to how to properly wire this would be great.
Matt

 

A gauge requires a sender, not a switch. A sender is big and a switch is small. Different sender makes have different characteristics and can usually not be interchanged. It is quite common to use a brass Tee to enable a sender to be mounted in addition to a switch, where there's only one port.
Why are you ditching the stock gauge, and why don't you just exhange the original sender (or switch as you called it) for the Autometer sender? If it doesn't fit in the hole then get a brass adapter.
Of course the oil pressure is not over 100psi with the engine off...

 

I can just drop the stock switch. I need tha tin place so the fuel pump will run. Ill have to try a T. Im ditching the stock gauge cause I have a high volume oil pump which reads past the stock gauge
Matt

 

Well the gauge sends out a voltage signal to the sender to check its resistance basically. If you have two sources using the same sender, they can conflict. I ran into this same issue with the LS1 and 4th gen fuel level sender. The PCM wants the fuel level for EVAP, and I couldnt have that and my autometer gauge hooked up at the same time. The sending voltage would conflict and cause the gauge to go wacky.

J.

 

Ok.
So you actually tried to hook a gauge to a switch? It didn't dawn on me, sorry.
Like ghettocruiser says you can't hook two things to a sender at the same time, and also a switch (for the pump) can't drive a gauge at all.
Yep, a T seems to be the only way for you to get a pressure reading from that engine.

 

do the T or switch ur fuel pump to a switch. easiest way.

switching to aftermarket gauges are best. stockers read like crap and if its a new motor dont do it.