My car will maintain a steady 85c with the air conditioning on at idle. If I turn the air conditioning off, the water temp will climb till 99c and then the fans kick in and begin the cool the temps down.


Why in the hell is my car running COOLER with a/c on than off? Any insight is appreciated, because I have no clue.

I have a fluidyne rad in place of the OEM

 

Ive read that the fans stay on with the a/c on Im not sure I hope someone that knows this for sure can chime in on this.

 

I think your right.

 

your right the fans do stay on when the a/c is on. my temps are 80c-85c with the a/c on and about 88+ without the a/c.

 

Turning on the A/C automatically triggers the relays that activate the radiator fans on low speed.

 

Any car I've been in that had a/c, the fans always turn on while the a/c is running.

 

If you were to push in the A/C button but not turn on your vents, would it still turn on your fans?

 

If you mean activate the cabin fan, no, the cabin fan needs to be at least in the "1" position for the A/C to operate (and hence, activate the radiator fans).

 

Im not seeing a 3 degree variance though... with the a/c on it will maintain 85-90 all day.

With out a/c, and before I had the PFC, it would shoot all the way to 108 before the fans would kick in.


Could it possibly be my thermostat is bad? On my water temp gauge (I have mounted on the 83mm tubing coming from the filler neck TO the radiator) it will read 94 but the PFC water temp reading shows 84-88.

My only guess is that the car's afrs gets thrown off when the a/c is off and likely running rich...

Like I said -- I am stumped

Also one other question for anyone that may have experience with this -- when I turn my car on from a cold start the PFC will read approx 14.4 volts, once the car is fully warmed it reads 13.8 volts..

 

Yeah thats what i thought.

 

my car is having the exact problem as yours. I always have to drive with the AC on in the #1 fan speed because it runs cooler with the AC on. I was having overheating problems until I noticed my fans don't kick in till the car is very HOT! So the AC manually turns on the fans at any given time. After I started doing that my car wasn't overheating anymore, if you know how to fix this let me know!! koyo rad + flex-a-lite fans are on the way so hopefully that will fix the problem or maybe my thermostat is peaced....

 

Another trick is to turn on the parking lights. This will cause the ECU to turn the fans on at a lower temperature than it usually would. You can also change the thermoswitch to an FC thermoswitch. Lowers the temperature at which the ECU activates the fans. I can't tell you what the different temps are, but I think it turns on about 10 to 15 degrees sooner than the FD thermoswitch.

 

I just wanted to make my third post so that I can send a pm to buy some rims.

 

you could always use a datalogit and check what coolant temp the pfc has the fans set to come on for. When i needed my car to pass emissions, we set the coolant temp higher in the pfc so it would run hotter, and then adjusted it back down after. It could be that the fan parameter is set too high, and you can fix the problem by adjusting the fan temp threshold lower.

 

hahahahahaah that is just hilarious!

 

Wow, I had no clue. I used to do this all the time. However, I did it because I thought the car looked cool driving with the parking lights on. Good to know... thanks!

 

do the FC thermoswitch, problem solved.

IIRC, someone made a 160* thermostat for FD's and FC's

 

Green manual is your friend - read


later

 

FC thermoswitch 95 deg. C
FD thermoswitch 108 deg. C

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/its-official-do-not-buy-miata-thermoswitch-until-you-read-397156/