Hi Guys,
I've been scouring the forums trying to find an answer to this, but have had no luck.
I've got an 85 Firebird that's been converted to RHD and had an engine upgrade for a 305 to 350 at some point in its life. It's also had the TPI intake and ECU installed, I'm assuming from the 305 motor in it originally.
It's also had about 3 motor transplants, the last one was 18 months before I purchased the car.
I've got low oil pressure and before I go looking at the horrible things that could cause it, I want to eliminate the least expensive things first.

That said, here's my dilemma. I have found the Oil sender/switch located just above the oil filter. It has TWO wires coming off it. My 85 transam has a 60psi electronic oil pressure gauge in it, and no dummy lights.

I've now been told the sender unit near the oil filter is ONLY the switch/light, and the actual pressure gauge is behind or near the distributor which sends the signal to the gauge.

What I'm looking for is a clear and simple explanation regarding the two.

I know there are 3 wire and 2 wire versions of the black plastic one with the plug, and there's a single wire "bell" version of the other.
Can someone please confirm or deny if the following is true:

a) 1 wire - oil pressure gauge (sends psi to gauge)
b) 2 wire - oil switch (lights dummy light/check engine on car)
c) 3 wire - combines both into one unit
d) a car with a TWO wire sender/switch MUST ALSO have a 1 wire gauge sender?

Any help would be greatly appreciated.