I havent looked at my sensors lately and two of them are Broke... My question is whats their purpose? The Switch that sticks out near the oil filter. Oil Pressure switch, I have one on the manifold also.. Why two? and theres a One Wire Switch thing near the oil dipstick (passenger Side). My electric Fans do not work, I hooked up a manual Switch. anyway why do i need these sensors? will I gain anything if I get new ones?

Thanks a Bunch!!!, Nick

Although, the quick search I did for you using "knock sensor" wasnt 100% clear.

The oil pressure switch above the oil filter is used on 90-92 thirdgens. GM moved the switch there because I think because oil was leaking out around the switch up behind the manifold on the 82-89 cars, and the new location is easier to remove/replace.
On 82-89 cars, the one behind the manifold is for the gauge on the dash, and the one above the oil filter is for the fuel pump. If the engine loses oil pressure, the fuel pump quits running. In '90, GM moved the gauge sensor to above the oil filter and combined the two sensors into one unit.
On the passenger side, the one-wire switch in the head is your fan temp switch. It controls the passenger fan on a dual-fan engine, and the only fan on a single-fan engine. Stock temp is about 235 degrees, I think.
The switch below it in the block is your knock sensor.

Hey Kevin, I think it was actually 82-88 that had the one up behind the manifold. My 89 only has the combined unit above the oil filter. I pulled a L98 out of an 88 a while back and it had the one behind the intake though.

My 89' had only the oil pressure sender down by the oil filter. There wasn't a sender behind the manifold of any sort, and i'm sure the car wasn't altered.

Ok, guess I was a year off. *blush*

Thanks guys.

That must be why my fan isnt working.. So whats the Unit on the front of the manifold? Has two wires, Right next to the thermostat.

Thanks, Nick

I beleive that one is for the computer