Hi to all from Homestead, FL. I'm new to the forum. I just got done rebuilding my 1990 Mazda Protoge 1.8 DOHC engine. All is running great, but for some reason my Coolant temp and oil pressure sending units are malfunctioning. The coolant temp sensor doesn't register at all, even after the engine has warmed up. The oil pressure sending unit remains on all the time. I have proper oil pressure. I may have switched the wiring, although I think that's highly unlikely. I have a Haynes repair manual, but the wiring diagrams don't depict the wiring schematics for these two sensors. Can anyone help?

Thanks.

Javier

 

Does sound a little improbable that the wires would be switched as the oil sender is on backside of block by the oil filter and temp sender is up front by the upper radiator hose connection.
A good indication that they might be switched is that the temp gauge would probablyregister full hot with key on, engine off but drop to full cold once you start the engine.
Both sensors use a single pin, single wire connection so switching could be possible. Wire for oil pressure switch is Yellow with a Red stripe. Wire form the gauge temperature sender is Black with a Orange stripe.