I bought the sensor that Pettit sells and all last year my car would run for ten minutes after shutting it off. I finally talked to Cam and was told to remove the 2 jumper harnesses which solved that problem. It turns my fans on at 88 deg. C and my car stays cool for the most part without any trouble. I was wondering though if anyone else knows anything about this sensor, is it as good as the FC switch? I'm curious if the FC one would offer any benefit to me?

 

Sounds like they have a lower temp thermoswitch. The nice thing with the FC thermoswitch is it plugs right in, uses the same connector and everything.

Wonder where they're getting their switch from...

Dale

 

I went through 2 sets of fans when I ran a Greddy FMIC (now running Vmount setup made by Speed of light). The car basically never ran colder than 95*C with the Greddy FMIC. The fans were setup to engage at 85*C on the PFC to make up for the inefficiency of the Greddy FMIC with respect to its restriction of air flow through the radiator.

First set were probably the original set with 123k miles. I bought the second set used so no idea on mileage.

85* to about 99* C is a pretty normal operating temp range for most cars. On my previous FD with a SMIC setup that allows the radiator to get good airflow, fans were OK at 130k miles.

 

PS - This is linked to from the FAQ thread.

Thanks for a great thread Dale.

 

helpful writeup Dale

 

we see a fair number of fan recall kits that have gone bad.

 

Well like any thing else, money spent on the cooling system is a must. My car has pretty good duct work, a M2 Large SMIC, Fluidyne Radiator, Water plus Water Wetter, and PFC set at 85C. It's getting around 100F here in FL on the pavement, about 93F ambient and I can drive in stop & go traffic at about 83-86C. Highest temp I've seen is 91C.

 

Which of the two sensors in the attached picture is the one that sends coolant temperature to the PCME, and which is the fan thermoswitch? This info is in neither the 1994 factory manual nor the 1994 parts catalog. Both part numbers are shown, but identification of both parts is the same! I have the FC fan thermoswitch on order, but would like to know which sensor I will have to replace.

Thanks!

 

the green one is the sensor for the ECU

the other one is for the fans

 

j9fd3s,

Thank you!

 

It will also be obvious to you when you have the new sensor in your hand.

The fan switch is the lower of the 2 sensors with the black, 1-wire plug going to it.

Dale

 

Awesome write up.

If anyone needs an electric fan I would recommend the Altima or Taurus fans. Those push big CFM's and are known to work much better thahn aftermarket fans.

And can be found at many junk yards.

 

so are both of those sensors signals for fan speed? Do they both need to be replaced?

 

mefarri,

No, only the lower one needs to be replaced. The upper one (green connector) sends coolant temperature info to the PCME, which sets A/F ratio, and also can change fan speed (I think), but it is set correctly for the FD.

 

Sounds like you have a 240 or FC background .

Those cars have clutch fans that are always a pain - in the way, rob engine horsepower, etc. Guys have looked for all sorts of alternative fans.

Again, the STOCK FAN WORKS GREAT. I can't see any reason why you'd use an Altima or Taurus fan.

Dale

 

I have done the FC thermoswitch modification myself and I have a few questions....

I noticed while cruising, im getting 180 degrees, and when I really get on it the highest temps I got are about 190-200 degrees F. Does that sound normal? If my car is running at 180 degrees, wouldnt I still be in closed loop and my ecu would think my car isnt warmed up and itll dump more fuel and make me run rich? I have an OEM thermostat.

I hope thats not true because I need to pass smog so im wondering how this switch will affect smog. I read someone on here who has the FC thermoswitch on his FD and passed smog running the engine only at 180 degrees , but he had an aftermarket thermostat that opens sooner too. do I NEED a thermostat that opens sooner to make this switch operate efficiently or.. I just wanna know how all this works

 

Ernesto13B, do your temps go above 200 if you simply have your car idling, it should unless it's cold (say under 50F) out? According to Dales info the FC termoswitch will make the fans come on when your coolant temps hit 97C (around 207F) rather than 107C (around 225F). So long as your car is running properly, you should pass, if you're worried that your temps are too cool, simply idle it to get the temps above 200 before pulling into the testing station...

 

Agree with f2racer.

Also, according to my 1994 RX-7 workshop manual, page TD-4, the stock thermostat begins to open at 80.5 - 83°C (177 - 182°F), and is fully open at 95°C (203°F). Those temperatures are independent of whatever fan switch sensor you use. So in normal (moving) operation, when fully warmed up your thermostat should hold your coolant temperature between 177 and 203°F. The 207°F fan switch for the FC won't affect that; it just means that if temp rises above 207°F that switch will turn on the fans. (BTW, the stock Miata fan switch also trips on at 207°F.)

 

I've noticed this, I've shut my car off and check it 10 minutes later and the water temp was at 99C.

I've seen so many people say so many different things for shutting the car down I never know what's right. One of the things I read is to let it sit for a bit, then start it and let the coolant cycle and then shut it back off. Is that worth doing or is that just another personal preference? I just don't like the idea of having 100C fluid sitting there.

As it is, the fans in my car are set to come on around 85-87C and it runs pretty cool. It gets to 95C a couple times but never for that long, usually it's 88-90 with the recent hot and humid days.

 

Yes if I let the car idle long enough my temps do go to 205F or 207F which ever one it turns the fans on at. Ok i just wanted to make sure that it was normal. I really love the cooler temps it makes my car run as cool as some cars that dont have turbos which= reliable.

I will def take your advice and warm the engine to 205 when I do the test, thanks!

 

Great write up Dale . More stuff added to my list to do to the car this summer while I have it taken apart.

and jmadams, thanks for that input as well. I'm assuming I have the problem you are speaking of since my AC turns on and off randomly no matter what setting it is on.

This thread is full of great information to help solve multiple issues. keep it coming!
-Justin

 

Sorry for the double post, but I'd also like to point out that Pettit makes a thermoswitch that kicks on at 85C! So if you're looking for ultimate cooling this might be the best option. Oh and it's also plug and play just like the FC one.

http://www.pettitracing.com/rx7/index_cooling.htm

-Justin

 

The 85C thermoswitch only makes sense on a car with stock ECU.

 

Since the stock thermostat begins to open at around 82°C and is fully open at 95°C, using a fan thermoswitch that cuts in at below 95°C does not make sense, IMHO.

 

Thermostat temp is really around 82 deg. C. The car should warm up, hit 82, and stop. That's what mine does most times in nice weather. 82 is a very comfortable engine temperature.

I do agree that a really low fan switch is a little weird. I prefer to have the fans slowly come up in stages. But, if you have a stock ECU, that might be worthwhile.

Would be interesting to find out what fan switch Pettit is using . I'm sure you can get it cheaper elsewhere.

Dale

Dale