I've got a 2016 XLT 3.5L EcoBoost and I have been the only owner. Very soon after I purchased it, I started having the infamous "high-fan" problem. Like everyone else, the dealer told me it was "normal" and kept dismissing me. I've been researching potential problems and performing any tests/repairs that were within my ability, but I'm not able to evacuate/vacuum the system.

I've replaced the pressure sensor, my coolant level is full, the A/C works well, and both fans work as expected. I've read where some people have had luck vacuuming the system and recharging it with fresh refrigerant and oil, I've read about people replacing expansion valves, orifice tubes, bad fan motors/relays/fuses, all of it. I think the fans are doing what they are supposed to do at the time they triggered... I think the condition that triggers the high-fan is what I'm hunting down. I've been driving F-150's and Super Duty trucks since the early 90's and I am very confident when I say that my truck should not "normally" trigger the high-fan anywhere near as much as it does.

I know enough to keep myself out of trouble, but I don't have a firm grasp on what the high and low pressures should be (accounting for ambient temperature). Monitoring some Ford PIDs in ForScan and OBD Link, my low pressure is ALWAYS exactly half of what my high pressure is. From the research I've done on R134a systems, it is my understanding that the low side should be between 30 and 55-60 with the high side being something like twice the ambient temp plus 50 degrees. With that in mind, my low side is out of normal range. Am I on the right track?

Prior to today, I was observing 225-250 on the high side with an ambient temp in the low 80's, and the low side would be exactly half of that. I thought it might be overcharged, or had too much oil from the factory, or any of the other reasonable guesses I've read about, so I had the system vacuumed and recharged today. Although the low pressure is now reaching far below what it had previously, it remained half of what the high pressure was, which is now as high as 300 with an ambient temp in the mid 70's. However, when the compressor cycles off, the pressure on both sides drops far more dramatically than it ever did previously. Instead of only dropping 15-20 on the high side, it now drops around 130 (one-time example).

My gut keeps telling me the expansion valve should be replaced since the system cools, has no leaks, and there don't seem to be any signs of a compressor failure.

The truck has been tuned, but the problem existed long before the tunes, and it has been consistent through the tunes I've used. The lower grill shutter has been removed due to physical damage from debris, so the actuator is completely disconnected and code is present, however, the problem existed before the shutter was removed. I have a good quality adapter for ForScan, though I doubt any of that will do any good.

Any input would be greatly appreciated. Like I said, I know the high fans are necessary under certain conditions, but kicking on the second you start the truck and running until several minutes after the A/C is off (or the truck is turned off) is not normal. That high fan is deafening and mildly humiliating in crowded areas and drive-thru's.

Thank you

 

Both sets of numbers are way off.

At 80ºF, you should see:

Discharge: 150-185psi
Suction: 34-44psi

At 70ºF:

Discharge: 126-160psi
Suction: 28-38psi

Pushing to that extra 80-100psi generates a lot of heat, causing the fans to run full out, and raising psi on the suction side. Sounds like a stuck TXV.

 

Finally! Some firm numbers backed by some confidence.

I'm just going to replace the expansion valve as suggested and since I now have some pressure values to aim for.

Just for kicks and giggles, what would a defective TXV look like after being removed?

 

After shutting down, it should take just minutes for the pressure to equalize. If it's taking a lot longer, like a half-hour, and the equalization rate is steady you've got a blockage between the condenser and low port. The txv is the only thing that sits between those points.

If the equalization is reasonably quick at first, then slows a lot but keeps equalizing, there is a blockage between the evaporator and condenser. The accumulator sits between them.

Another sign of blockage at the tvx: When the compressor starts, the low side will drop quickly, but the high side will be slow to rise. The run between the txv and compressor suction is a small percentage of the system, with most of the gas being between the compressor discharge and the txv. As gas is slow to move through a blockage at the txv, the compressor just doesn't get gas to to pump, so low side pressure drops, but high side builds slowly.

 

 

Your fans running all the time on high can be caused by a lot of things. When mine did it, it was caused by a bad fan relay and both fans were replaced, all returned to normal. Others here have seen their systems do it after the A/C system had been "over charged." Others found their coolant low, which led them to discover o-ring leaks or degauss bottle leak.

I would first determine if there is a correct A/C charge on the system by evacuation and re-charge. A quick visual look can see or smell coolant leaks,

 

Thank you for the input.

I found mention of the items you mentioned across several sources and checked everything accordingly.

• The coolant level is full, and has maintained that level for a very long time.
• The fans both activate and deactivate as they are commanded by the computer, but I’ve also switched around the relays just to be sure.
• The final and most recent step of troubleshooting was to evacuate the system, vacuum it, and charge with fresh R134a/oil. My system was actually slightly undercharged. The pressures are still too high and I can only assume that’s what’s triggering the high-fan condition.

I hate to have to ask my guy to evacuate the system again so I can install the TXV, but I’m bothered so much by that loud fan that I have to take some chances.

 

Unfortunately, it wasn’t the TXV. After evacuating the system and replacing the TXV, the problem still persists. The high fan runs way more than it should, but I think it’s doing so because of the pressures within the system. The high fan does switch off from time to time, but it’s erratic and sometimes comes on for 2 seconds and switches off.

My pressures now reach as high as 400-425psi at 85F. The vents blow cold, so I’m back to chasing down whatever is causing high pressures.

 

Where are you located and what is your ambient temperature?

 

Keep us updated. I'm having the exact same issue.