because they are dicks

the stock oil pressure gauge and sender are both garbage. fact.



http://pengaru.com/~swivel/cars/rx-7/ops/w_IMG_3221.JPG



do you want a schematic too? Or would you rather have the method of operation explained, it took us a long ass time to figure it out.

A real man could do it with a full-seized wrench. https://www.nopistons.com/forums/pub...>/rolleyes.gif

Pengs pulling out the big guns https://www.nopistons.com/forums/pub...IR#>/bigok.gif

I was just being a wise ass

I see no variation in readings from my stock gauge and

my mechanical aftermarket actually, but then again

mine still works and isnt pinned.

more like the big pics lol



seriously though, that sender is a complete disaster, there are others that have been used just like it in the past and even on some current cars and they are known for being shitty and unreliable.

Out of 6 FC's I've had, I had one go bad with the "pinned" problem, but I was able to fix it. I think that if you don't modify anything the car is happy. Mazda actually has a warning about installing CB radios in the car. They say that if you mess up you could also mess up the fuel injection system. I would assume that the same goes for an aftermarket stereo.

alright i stand corrected, i'm just speaking from experience, and out of all the rx7 owners in toronto, no one has said anything about their oil pressure senders failing.



I only speak from my own experience.

I really doubt that the sender is crap. I have the exact same sender (well, might be different resistance range) on my 4Runner, I have worked on and helped work on dozens of Toyota trucks, and have known hundreds of Toyota truck owners, and I have never heard of a bad sender unless it gets damaged. What *is* a weak spot is the unprotected and relatively weak wiring connector. On the trucks, it came with a plastic sheath that covered the connector and sender, and held them firmly together. I think that the weak connection could be a major cause of issues. I also wonder if the actual oil region on the block where the sender goes has issues...I had a case where there was some crud caught in there, my gauge would randomly go between zero pressure, pinned pressure, and correct pressure. I think there was something in that oil passage that was intermittantly blocking/unblocking the sender.



I don't doubt that the factory guage might very well be a weak link too.

The picture above is the internals of the sender on our fc's, it's a crude design, believe it or not, it's electro-thermo-mechanical. Thats right, the current flows through a heater element in the sender to bend a bimetallic strip which doubles as a switch. When the circuit is closed (bimetallic strip resting on a terminal slightly visible in the picture) the current flows through the heater wire, causing the strip to bend from the heat generated. When it bends enough to lift off the terminal, the circuit opens and it cools, straightening out eventually closing the circuit again. this process repeats itself the entire time the sender is functioning.



Now, the way oil pressure affects this thing, is the terminal on the bottom that the bimetallic strip rests on, moves when pressure changes. There is a plate which deflects with pressure at the base of the sender, this plate pushes the terminal up and down, this in turn changes the frequency at which the circuit will cycle.



So there you have it, the sender outputs a switching current crudely generated by something directly effected by temperature. The gauge side has a bimetallic strip/heater wire setup also, higher frequency == higher average voltage == more deflection of the bimetallic strip @ the gauge == higher pressure displayed. Ever wonder why the thing seems to respond slower when it's cold out?



You can imagine the confused look on my face when we discovered the wire wrapping that plate was a heater element inside the oil pressure sender, now I want to frame the part photographed above and hang it on the wall for the EE types to stare at for hours trying to figure out wtf it is / does, then laugh hysterically when reveal what it is.



BTW, thanks go to ikrazygluebrokenapexseals for contributing to the reverse engineering of this ridiculous thing.