The oil pressure switch on the R21 failed in a spetacular manner, dumping a LOT of oil out the side of the block... Am now in the process of finding a replacement...
Have some R25 units, but they have an integral pressure gauge sender, so no good there. Fuego sensors only have one lead (ie normal).
The R21 has two.
Now the odd thing is that one appears to serve no function I can determine. It has no resistance to ground, has no voltage supplied ignition on or off, and does not illuminate the oil light when bridged to the other wire.
The other seems to function as a single wire sensor connection - ie illuminate the oil light when connected to ground.
Any ideas on what this is all about? An oil pressure signal to the ECU perhaps? The Haynes manual ties to tell me the R21 should have a single wire sensor, as do the parts websites when i plug my model in...