Focus Fanatics Forum banner

1 - 7 of 7 Posts

·
Registered
Joined
·
34 Posts
Discussion Starter #1
Ok so ive been dealing with this for about a week already. Car is a 2003 svtf and my fans will not come on without a/c on which causes overheating while sitting. So everything cooling wise, minus the rad and fan assembly, is brand new since i built the cyl head a while ago wp, thermo, thermo housing, cts, fan resistor, resistor pigtail have all been replaced. Also have done about 5 flushes total just incase anything was in the water jackets and plus it sat for a year. Anywho with the a/c off after driving and idling the temp clibs to about 228f with no fans, which is almost to the red on water n oil temp, turn the ac on and both fans turn on and temp goes back down to rougly 197f-195f and is normal. Did the old jumper-rooskie from rl15 to f1 with key on n both fans engage with resistor plugged or unplugged. Oh and it has heat even when cold so no bubbles in system. When the car was tuned i dont believe fan temp was ever messed with but no way checkin now since my xcal was stolen by my old awesome roommate. Any suggestions on what is goin on or anyone dealt with something similar?
 

·
Registered
Joined
·
1,236 Posts
Have you checked the ECT sensor in the thermostat housing?

When you were jumpering did you get the fans to run in low and high speed?

The PCM controls the fans by grounding the control side of the low and high fan relays after input from either the ECT sensor or the AC control circuit.

Paul
 

·
Registered
Joined
·
34 Posts
Discussion Starter #3
Im going to take a look at the ect in the mornin...who knows i could have got a bummed one but no cel and i get a tempreading but ill double check it tomorrow.
As for the fans i should have clarified but they only work on high speed when jumped or with ac on.
 

·
Registered
Joined
·
16,182 Posts
Was going to say your temp mentioned there leans toward low fans not working but high are.
 

·
Registered
Joined
·
34 Posts
Discussion Starter #5
So i checked the low speed relay and it tested fine. Now on the ect, when plugged in i get temp reading no fans, unplugged i get the opposite, fans no temp. Now is it possible to have temp reading but no imput for fan control and is there a certain way to test this sensor?
 

·
Registered
Joined
·
34 Posts
Discussion Starter #6
Ok so i pulled the sensor, there was a bit of build up on the probe end, prolly since it sat for a year, so cleaned it off and tested resistance. So room temp 70f was approx 23.2ohms, 35f sensor climbed 57+ohms, 200f resistance dropped to 4ohms steady. Idk if that is within spec but resistance did drop while heating the sensor.
 

·
Registered
Joined
·
1,236 Posts
So i checked the low speed relay and it tested fine. Now on the ect, when plugged in i get temp reading no fans, unplugged i get the opposite, fans no temp. Now is it possible to have temp reading but no imput for fan control and is there a certain way to test this sensor?
Bench testing the fan relays is good, but not enough. You need to verify the fan circuit downstream of the relays. The way to do this is to remove the relays and jumper across the load contacts at each relay socket (one at a time) to verify the low and high fan circuits downstream of the relays is intact. BTW the fan power circuit is always hot, no need to have the ignition on.

I believe the reason the fans run if you remove the sensor (open circuit) is that is a failure strategy in the PCM, but with no resistance reading the gauge cannot function.

The reduction of resistance with increasing temp is basically correct but Ive yet to find a reliable source for the temp-resistance curve for these sensors. The PCM reads the resistance and uses it for both the temp gauge in the IC and for operating the fans by grounding the control side of each relay.

Paul
 
1 - 7 of 7 Posts
Top