Ranger

Hey there, I'm trying to sort out a couple of cooling-related quirks that my FD has and hoping someone here can help. I'm relatively new to FDs (and RX-7s in general), but not new to cars, so feel free to get technical with your answers. I'm also a visual learner so any pictures when trying to describe something would be great This is for a '93 touring model with a fresh rebuild, Fluidyne radiator, Pettit aluminum AST, and a Power FC.



Issue #1: Low coolant buzzer. It goes off constantly. This started happening randomly when I started it up one day, after a couple thousand miles of breaking in the new engine. Coolant is NOT low. I have flushed and burped it several times. It's definitely not eating coolant.



Issue #2: Power FC commander does not read the correct water temperature. I never had this problem until I got the car back from having the new engine installed. Warm idle temp displays around 28*C, and it never goes over 35*C or so. Any idea where the ECU (and/or FC Commander) gets its reading for the coolant temp? My guess is that this is causing all kinds of bad problems---including running super rich and preventing the fans from coming on (they never do come on).



I should note that I just replaced all the coolant related sensors on the water pump housing---coolant level sensor on the front, coolant temp sensor on the back, and the thermoswitch on the back. I want to have my car tuned, but not until I get this fixed! Thanks in advance

Signal 2

#1. Check the lead and plug to the coolant level sensor. If those look OK, maybe just buy a new sensor (IIRC, they're not that much...~$20). I know you said you've burped it several times, but the only othe explanation is air in the system.



#2. The PFC gets it's temp readings the same place as the stock ECU...from that top sensor on back of the waterpump housing. Those wires are notorious for being a little on the fragile side. You might want to double-check everything you did back there. Since you replaced all of them, but none seem to be working properly it almost sounds like the WP housing isn't grounding to the engine block. But that seems almost impossible.

A last thought is to maybe check continuity between the sensor leads and corresponding pins at the ECU. Do you have a FSM yet?

GreyGT-C

since it's a new engine in the car and you said that you've already replaced all the associated sensors, most likely one of the super brittle wires in the harness is broken somewhere. I used to know where the wiring schematics were online, but i don't anymore... maybe someone can point you to the right location for it. I'd get a multimeter and start tracing wires from the coolant sensor on the back of the t-stat housing all the way to the ECU. Same for the low level sensor.

Ranger

Thanks guys. The wiring harness is old and not in very good shape either, so that's my best guess. I may end up buying a new wiring harness...but until then I will try to trace the wires back to the firewall. Also, I just replaced the coolant level sensor as well...that was the first thing I did actually.



I do have an FSM (got it from http://www.wrex-racing.com/web/fd/info.htm), but from what I can tell it's not very good concerning this particular problem. Maybe I'm not looking in the right location...but I often find the FSM (or at least the ones I've found online) to be inadequate. There is some info on E-16, but that only discusses one of the sensors. Can't find anything related to the ECU...can someone point me in the right direction?

Signal 2

For posterity, an update on thread RE: odd PFC temperature readings.....

The OP accidentally had the wires reversed for the temperature sensor and thermosensor.