I have had a problem with engine runnign too cool for awhile. Had shorted fan that would come on at 49c, etc. Anyway, the problem now is this:

I can;t get temps above liek 76C (ambient 70F) when driving on highway, of course at stop and go it will rise until 95C then fans come on. I thought first that my themostat was stuck open. I replaced it, and it actualluy got cooler(new one works better).

I am at a loss, the only thing I can think o fis the thermo-sensor that reads temperature. Has anyone had this go bad and become skewed? Could it be anything else?

Thanks

 

First of all:

76C = 169F

95C = 203F

What water temp gauge are you using, and maybe its going bad.

 

I know, I am using 82C thermostat. The temp gauge is my PFC.

problem is the extra fuel it adds at that low of temp (76C)

 

Either the thermo-sensor or -switch are going bad.

The Miata 207F thermoswitch is N350-18-840.

The thermosensor is N3A1-18-840.

By the way, the only difference between the water and fuel
thermosensor is the seal. One has a crush washer and the other
has an "O" ring.

 

Since we are talking about Thermoswitches...what does it take to swap out the RX7 thermoswitch, and put in the Miata one?

Is the thermoswitch the only part you need? And where is it located?

Any how-to on the web...????

Thanks,
Patrick

 

The Miata TS has the same threads as the stock one. But, it uses a different connector. I used a simple spade connector spliced into the stock wire.

 

My thermosensor went bad the other day, I just went and picked one up about an hour ago and on my back the car would die on me and take several attempts to get it running again, also large clouds of blue smoke when it wouldn't start.

Am I having the same problem, not reading correct temps and duming alot of fuel??

 

Hey Chuck (or who ever would know) what are the functions of the thermosensor and thermoswitch? And what are the symptoms of each one going bad? I would appreciate a brief explanation of both. I've got a shop manual for 93FD, could u point out what section its in? Also what are the benifits of switching to the Miata thermoswitch vs. stock FD switch? Thanx again Tony

 

The h2o thermosensor tells the ecu what temp the coolant is at, and the ecu alters the fuel map for the temperature differences. The fan thermoswitch activates the fan relays at a given temperature. If either goes bad it will trigger your check engine light. I had to replace my h2o thermosensor this summer, it was causing my car to run overly rich and flood my engine at low rpms. If the switch goes bad, then your fans won't turn on because of the temp. The advantage of the Miata thermoswitch is that it will trigger the fans to come on a lower coolant temperature than the stock one. This will in turn help to keep the car a bit cooler. You can check in the manual under F-158.

eric

 

the thermoswitch is a last ditch high fan speed that comes on at 226F. thermosensor just tells temp to ecu

 

okay, dealer says no N3A1 18-840 only either 18-840C #1, 18-840C #2, or18-840C #3. I think no. 1 is the thermoswitch, no. 3 goes in the top of housing, and no. 2 from back.Which is thermosensor?

Thanks guys

 

Thermosensor is on back close to alternator (have to take off crossover tube). I just replaced mine and car is acting like normal, not dying or anything.

Basically the thermosensor can cause your car to act up if it is bad.
$43 from www.rx7.com cheapest I found

 

I'm still trying to find what the hell is wrong with my idle hea.. When I start my car, after the AWS kicks in, my engine will just stumble and shake like crazy, then it gets a little better after 1-2 minutes.. could this be the water thermosensor???

 

Yes, it can. Wierdly enough I didn't suspect the thermosensor cause eveyone was saying the car will idle like ****, drive liek ****, etc. mine didn't ran great(for the most part) just temp issues.

Anyway, thought I woudl give the update since someone brought this thread up again. My water thermosensor, not the switch, was bad. it was off my 5 degrees all the time.So when I thoguth fans were coming on at 95C ther were actually coming on at 100C, adn car wasn;t actually 76 c on highway, but more like 81 or 82C. it was fixed immediately when I replaced it.

Moral of the story, if you see wierd temps, or car runs poorly, test the sensor. it isn't hard to pull and testing procedure is in the manual.

 

So is this what was wrong with your car the whole time!!!

On a side note I'd like to relocate my air temp sensor to either my Greddy elbow or the throttlebody.

Anyone have any idea if I can just splice into the wire to extend it so it'll reach to say my Greddy elbow? I have a feeling the sensor heat soaks and would like to more my sensor to test this.

Thanks,
STEPHEN