cooling fan issues

[POHRacing]

I’m looking for some guidance on my cooling fans. I have a lot of experience working on older Ford vehicles, and some of that carries over but I’m not as educated on the newer Fords specifically with their computer strategies. Since I purchased my 2014 XLT 3.5 (used, 70,000 miles) the ac has left much to be desired at in the summertime at idle, but at cruising speeds was ice cold. I started by checking the engine operating temperature but even in 100* heat the operating temps never went above 190* with the ac on. The ac pressures on the other hand were pretty high with 55psi low side and 275psi high side at idle, which explained the balmy vent temps. After a few months of dealing with it and convincing myself it was a mechanical issue, the low side suction line developed a pinhole leak and I also found out the condenser was clogged. I went ahead and replaced the compressor, condenser, hoses, and expansion valves, but noticed something while I was vacuuming down the ac system and purging air from the cooling system (also replaced the thermostat with a 180*). With the ac off the cooling fans do not kick on at all until the operating temperature gets to 212*, and even then it’s only the low speed fans. The low speed fans come on immediately with the ac engaged, but the high speed fans never activate (not even with the ac on MAX). I went ahead and charged the ac system as is, and now at idle the vent temps are down to 30* at idle with a perfect pressure of 35psi low and 200psi high (70* ambient). I’m stumped on the high speed fans though. I can activate the high speed fans by manually making the connection at the #14 relay, so I know it’s not the fans themselves, and I’ve swapped out the relays with known working ones with no luck. My long winded questions about the cooling system are:
1. What has to happen before the computer activates the high speed fans?
2. Should the operating temp go up to 212* before any fans turn on?
3. With a 180* thermostat installed, what should the target operating temperature be?
Thanks in advance for any input.

 

[imp]

I’m looking for some guidance on my cooling fans. I have a lot of experience working on older Ford vehicles, and some of that carries over but I’m not as educated on the newer Fords specifically with their computer strategies. Since I purchased my 2014 XLT 3.5 (used, 70,000 miles) the ac has left much to be desired at in the summertime at idle, but at cruising speeds was ice cold. I started by checking the engine operating temperature but even in 100* heat the operating temps never went above 190* with the ac on. The ac pressures on the other hand were pretty high with 55psi low side and 275psi high side at idle, which explained the balmy vent temps. After a few months of dealing with it and convincing myself it was a mechanical issue, the low side suction line developed a pinhole leak and I also found out the condenser was clogged. I went ahead and replaced the compressor, condenser, hoses, and expansion valves, but noticed something while I was vacuuming down the ac system and purging air from the cooling system (also replaced the thermostat with a 180*). With the ac off the cooling fans do not kick on at all until the operating temperature gets to 212*, and even then it’s only the low speed fans. The low speed fans come on immediately with the ac engaged, but the high speed fans never activate (not even with the ac on MAX). I went ahead and charged the ac system as is, and now at idle the vent temps are down to 30* at idle with a perfect pressure of 35psi low and 200psi high (70* ambient). I’m stumped on the high speed fans though. I can activate the high speed fans by manually making the connection at the #14 relay, so I know it’s not the fans themselves, and I’ve swapped out the relays with known working ones with no luck. My long winded questions about the cooling system are:
1. What has to happen before the computer activates the high speed fans?
2. Should the operating temp go up to 212* before any fans turn on?
3. With a 180* thermostat installed, what should the target operating temperature be?
Thanks in advance for any input.

PCM schedules "fan-on, fan-off", based on engine coolant temp. climb, engine speed and load, head temperature, oil temp., etc. So, fans do not typically operate under identical conditions all the time. After buying my '94 Mustang GT, 5.0, during a day with 110` temp, I noted while driving it around, fan turned on at far higher gauge reading than I liked, top of gauge travel almost, then ran until gauge indicated way down toward it's low end, when the fan shut off. This cycle took about 10 minutes altogether, subjecting everything to a thermal cycle not usually recommended engineering-wise. Reason it's done is to limit number of fan cycles, to allow reasonable long life of relay contacts and fan motor. Temp. could be more closely controlled by shortening this "differential" cycle; at 5-sec on, 5-off, temp might remain almost constant. Thus, this is a constant air flow system: max cooling flow of air "on", none when "off".

Enter the clutch fan: provides infinite control of air flow, from max to none, at all times. Much sharper "tuning" of engine operating temp., far more desirable. I ripped out the fan and installed a good thermal clutch and husky fan blade. Holds temp. almost constant from highway cruise to idling with ac max in 110` ambient air. Not easy job, though.

 

[MrQ]

PCM schedules "fan-on, fan-off", based on engine coolant temp. climb, engine speed and load, head temperature, oil temp., etc. So, fans do not typically operate under identical conditions all the time. After buying my '94 Mustang GT, 5.0, during a day with 110` temp, I noted while driving it around, fan turned on at far higher gauge reading than I liked, top of gauge travel almost, then ran until gauge indicated way down toward it's low end, when the fan shut off. This cycle took about 10 minutes altogether, subjecting everything to a thermal cycle not usually recommended engineering-wise. Reason it's done is to limit number of fan cycles, to allow reasonable long life of relay contacts and fan motor. Temp. could be more closely controlled by shortening this "differential" cycle; at 5-sec on, 5-off, temp might remain almost constant. Thus, this is a constant air flow system: max cooling flow of air "on", none when "off".

Enter the clutch fan: provides infinite control of air flow, from max to none, at all times. Much sharper "tuning" of engine operating temp., far more desirable. I ripped out the fan and installed a good thermal clutch and husky fan blade. Holds temp. almost constant from highway cruise to idling with ac max in 110` ambient air. Not easy job, though.

Its funny how most people here (including me) who modify their explorers, want the opposite.

 

[peterk9]

Welcome to the 5th gen Forum POHRacing.
The Explorer also has a cabin temperature sensor. I'm not sure if that only regulates the HVAC motor speed or if it is also in the mix for the cooling fan speed.

Peter

 

[POHRacing]

PCM schedules "fan-on, fan-off", based on engine coolant temp. climb, engine speed and load, head temperature, oil temp., etc. So, fans do not typically operate under identical conditions all the time. After buying my '94 Mustang GT, 5.0, during a day with 110` temp, I noted while driving it around, fan turned on at far higher gauge reading than I liked, top of gauge travel almost, then ran until gauge indicated way down toward it's low end, when the fan shut off. This cycle took about 10 minutes altogether, subjecting everything to a thermal cycle not usually recommended engineering-wise. Reason it's done is to limit number of fan cycles, to allow reasonable long life of relay contacts and fan motor. Temp. could be more closely controlled by shortening this "differential" cycle; at 5-sec on, 5-off, temp might remain almost constant. Thus, this is a constant air flow system: max cooling flow of air "on", none when "off".

Enter the clutch fan: provides infinite control of air flow, from max to none, at all times. Much sharper "tuning" of engine operating temp., far more desirable. I ripped out the fan and installed a good thermal clutch and husky fan blade. Holds temp. almost constant from highway cruise to idling with ac max in 110` ambient air. Not easy job, though.

Thanks for weighing in... That's what I was afraid of, and it's funny you mention the SN95 Mustang because some of the strategies in this Explorer PCM remind me of the EEC-V in my 95 GT. That car was fun to drive in open loop, but the second it reached operating temperature (over 180*) it pulled timing out pretty aggressively and became a slug. Same thing with this 3.5, it's fun to drive for about 15 minutes lol. I ended up using a DCC fan controller in order to keep the operating temps right at 180* in my Mustang, I wonder how mad my computer would be if I did that in this Explorer. I have FORScan, but I don't think I can do anything with the fans except monitor their duty cycle. It just doesn't seem like I'm asking too much to have a consistent operating temperature.

 

[POHRacing]

Its funny how most people here (including me) who modify their explorers, want the opposite.

EXACTLY!

 

[POHRacing]

Welcome to the 5th gen Forum POHRacing.
The Explorer also has a cabin temperature sensor. I'm not sure if that only regulates the HVAC motor speed or if it is also in the mix for the cooling fan speed.

Peter

Thanks Peter. That's a good point, and I haven't looked at the evap temp sensor to see if it's even accurate. I think there's a PID for that in FORScan though. I've heard of them being off by up to 20* in some cases, so I'll check it out.

 

[imp]

Its funny how most people here (including me) who modify their explorers, want the opposite.

Evidently, many desire to change modify things. Encouraged by outside influence, the thought prevails that the engine makers seek to cut corners wherever possible. I was trained to be analytical; took me till age 33 to get my Engineering degree, but I believe in what those smarter than I say.

 

[POHRacing]

Evidently, many desire to change modify things. Encouraged by outside influence, the thought prevails that the engine makers seek to cut corners wherever possible. I was trained to be analytical; took me till age 33 to get my Engineering degree, but I believe in what those smarter than I say.

Without getting into a lengthy existential discussion about why we seek to modify stock vehicles, I’ll respectfully submit that we who modify them simply have different and more specific goals than the original engineers intended. It has nothing to do with thinking the engineers cut corners, but the same engineer who painstakingly designed a headlight to balance efficiency, brightness, longevity, heat load, safety, etc... also had to value engineer it for mass production and make it fit within the parameters of the prevailing final vehicle design. I, an end user with very specific goals for my driving experience, don’t care for the resultant dim headlights. I have the options and knowledge base to properly modify them to better suit MY needs... so I do. The same can be said for every single aspect of a vehicle, including the cooling system. If the above assertion is wrong, then we would all just be driving the exact same vehicle.

 

[MrQ]

Without getting into a lengthy existential discussion about why we seek to modify stock vehicles, I’ll respectfully submit that we who modify them simply have different and more specific goals than the original engineers intended. It has nothing to do with thinking the engineers cut corners, but the same engineer who painstakingly designed a headlight to balance efficiency, brightness, longevity, heat load, safety, etc... also had to value engineer it for mass production and make it fit within the parameters of the prevailing final vehicle design. I, an end user with very specific goals for my driving experience, don’t care for the resultant dim headlights. I have the options and knowledge base to properly modify them to better suit MY needs... so I do. The same can be said for every single aspect of a vehicle, including the cooling system. If the above assertion is wrong, then we would all just be driving the exact same vehicle.

I call that a treatise on vehicle modification if I ever heard one.

In all fairness, the bean counters cut corners, but the engineers must also design for ease of assembly and work within the parameters that the EPA, the NHTSA, and their budgets allow. Throw in some administrative meddling and it's no wonder that there are improvements to be made.

Certain modifications are known improvements over stock, this is not to say that everything is designed poorly, but that there are definitely design restrictions on vehicles that create opportunities to improve reliability, power, aesthetics (personal taste not withstanding), fuel economy, and capability.