93 Radiator Fan turning on very often

billcu

Head Moderator
Staff member
Does the 93 ECM programming cause the radiator fan to run more than the other gen 1's? Mine runs more often than my 94's, it doesn't overheat or run hotter than the 94's though. I know the gen 2's are different because they often turn on at red lights when my gen 1's don't. The other possibility is maybe my 93 temperature sensor is off a little compared to the 94's, does anyone know which temperature sensor controls the radiator fan?IMG_3997 (Large).JPG
 
... does anyone know which temperature sensor controls the radiator fan?
As I remember, the drivers side temp sensor in the coolant crossover tube should be the single wire type which is for the instrument panel engine temperature gauge only. The temp sensor on the passenger side with a 2-wire harness connector is connected to the PCM which controls the radiator fan via the VCRM.

I can't say I've noticed the '93 radiator fan running more than others but mine are all modified so that may not be relevant.

It's been a while, but I recall in stock form, the '93 commanded the fan to come on at 215 degrees coolant temperature? You could check the temperature the fan comes on with a IR temperature gun. :unsure:
 
As I remember, the drivers side temp sensor in the coolant crossover tube should be the single wire type which is for the instrument panel engine temperature gauge only. The temp sensor on the passenger side with a 2-wire harness connector is connected to the PCM which controls the radiator fan via the VCRM.

I can't say I've noticed the '93 radiator fan running more than others but mine are all modified so that may not be relevant.

It's been a while, but I recall in stock form, the '93 commanded the fan to come on at 215 degrees coolant temperature? You could check the temperature the fan comes on with a IR temperature gun. :unsure:
I finally measured the temp at the crossover pipe, it was 230 degrees when the fan was running. It wasn't that hot out and the car wasn't overheating, the temp gage was below the middle point. My other cars don't seem to run the fan as often, maybe the thermostat is not opening all the way?
 
I finally measured the temp at the crossover pipe, it was 230 degrees when the fan was running. It wasn't that hot out and the car wasn't overheating, the temp gage was below the middle point. My other cars don't seem to run the fan as often, maybe the thermostat is not opening all the way?
The fan should've come on before 230 degrees?

I suppose it is possible the thermostat is not opening all the way. Another possibility is that it is the wrong thermostat(i.e. not the 4V thermostat). Either would in effect 'short-circuit' the coolant flow via the bypass and result in not having full flow through the radiator.

You could also have a partially blocked radiator (internal) which would decrease the cooling efficiency. Airflow restriction due to a blocked AC condenser could also be possible.

It appears the car is actually running at a higher temperature than what is indicated in the instrument panel (or what the PCM believes). Even so, the cooling fan should not be on very long before it cools down and shuts off if it's not that hot out.

The shop manual should call out the temperature sending unit resistance at different temperatures, so you should be able to test your temperature sensor with an IR temp gun and compare the results.
 
Yes, the fan was running while I was driving up my road. I'm not sure exactly what the temp was when the fan came on. I'll check those things out that you mention. Do you know a good source for the correct thermostat? It might have been changed by the previous owner.
 
The stock thermostat is Motorcraft RT-1110, which is a 190 degree unit available at most parts stores and online sources.

I personally am a fan of the Reische Performance Ford-4D thermostat, a 170 degree thermostat.

MotoRad is also a good brand which is an option listed on RockAuto.

Whichever you choose, it is highly recommended to test it first. ;)
 
For performance applications, it is recommended to have the PCM reprogrammed to have the fan come on 20 degrees higher than the thermostat setting. This is based upon the operating theory that the thermostat is fully open at this temperature. Without any change to the PCM, the fan will be triggered to come on at the stock temperature setting without any regard to the thermostat opening temperature.

In your particular case, the fan should technically run less with the 170 degree thermostat, that is presuming no other deficiency of the cooling system.
 
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It's been a while, but I recall in stock form, the '93 commanded the fan to come on at 215 degrees coolant temperature? You could check the temperature the fan comes on with a IR temperature gun. :unsure:
The fan was on today when the top radiator hose was 190 degrees, the bottom hose was 140. The heat was hot in the car but the car has never overheated. 190 sounds a lot lower than the 215 degrees you mention, is it possible the temp sensor that controls it might be bad? The temp gage in the car always seemed to read lower than my other cars, but it seems to do that more when the fan is running.
 
is it possible the temp sensor that controls it might be bad? The temp gage in the car always seemed to read lower than my other cars, but it seems to do that more when the fan is running.

The sensors are pretty reliable, but after all they are 30+ years old? In my experience most sensors degrade or 'drift' over time.

This is what the temp gauge in my '93 correlated to back in 2004:

N-
O-
R-215(Fan turns on)
M-200
A-180
L-160

How does yours compare?

I noticed on the trip back from Carlisle today, my Mystery Mocha Kenne Bell '93 mostly ran right at the "A" on the gauge climbing to mid span between the "R" and "M" on the gauge when running up long grades under pretty good load. Pretty much what I would expect, though the ambient air temps were only around 80 degrees. Despite being a modified car, I would bet the temperature sensor(s) and thermostat are original.
 
My gage is usually around the A and L also but the fan is often running then. I changed the thermostat yesterday, I changed the whole housing from a spare I had because I previously had trouble breaking the bolt that holds the housing together. Luckily the previous owner replaced all the hoses and used band clamps everywhere (not a good idea but handy in this case). I drove it a little and the fan didn't come on until I was back in the driveway and let it idle a bit. The gage was in the same area as before but it was a little cool out so I'll test it some more.
 
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