Automotive Air Conditioning Information Forum

A friend replaced a leaking condenser on this truck and brought it to me for a recharge. Pressure tested with nitrogen and it held so I vacuumed the system. It was below 500 microns and it held that so I charged it with 24 ounces of refrigerant. Pressures were 38 and 225. Temp outside was 90 and humid. The very best vent temp I got while driving was 48.3. It seems like the compressor is cycling too much. I read on the internet that this is an issue with this model truck and it’s because of they way Ford has the computer set up. I saw some information where people were adding a resistor to the wire going to the temp sensor for the evaporator.

48 would be an ok vent temp if it would stay in that range, but as soon as it gets to that temp, the compressor cycles and the temp jumps 5 or 6 degrees.

Has anyone else ever ran into this?

Dgreen wrote: ↑Mon Aug 16, 2021 12:49 pm A friend replaced a leaking condenser on this truck and brought it to me for a recharge. Pressure tested with nitrogen and it held so I vacuumed the system. It was below 500 microns and it held that so I charged it with 24 ounces of refrigerant. Pressures were 38 and 225. Temp outside was 90 and humid. The very best vent temp I got while driving was 48.3.

According to the specs that I have, 24 ounces of refrigerant is the correct amount, but the low-side pressure seems elevated. As far as you know, has the TXV ever been replaced?

Before the condenser gave out and was replaced, do you happen to know what the center vent temperatures were? Did the vehicle's owner voice any complaints about the A/C not cooling enough previously?

Dgreen wrote: ↑Mon Aug 16, 2021 12:49 pm It seems like the compressor is cycling too much. I read on the internet that this is an issue with this model truck and it’s because of they way Ford has the computer set up. I saw some information where people were adding a resistor to the wire going to the temp sensor for the evaporator.

I've heard a similar story in that some owners disconnected the evaporator temperature sensor and installed a resistor in its place. Never having done that, I can't say whether it works. However, if the TXV was replaced with an aftermarket part, it could be out of spec or malfunctioning. That has happened to me a few times.

older Fords are know to have defective cycling switches

Original complaint was it just wasn’t cool enough. Vent temp was in the high 50s. I added a couple ounces of refrigerant before I noticed
a big oily spot on the condenser. Owner of the truck installed a new condenser and I pressure checked, vacuumed, and recharged.

I think this truck still uses an orifice tube. There isn’t a low pressure switch in the low pressure line. There is a switch in the high pressure line.

I ran across the resister fix. That may be the direction we go.

If it's a CCOT system with an accumulator, I would check the OT first. Someone could have installed an incorrect part (too large of an orifice) or an aftermarket variable OT that just won't work right in that vehicle. The OT could also be clogged up, although if it was, I would expect to see very low pressure on the low side or even a vacuum reading. If it has an accumulator, it should have a low-pressure cycling switch mounted on it.

It doesn’t have an accumulator. It has a dryer on the side of the condenser.

Should be a block style TXV on that truck.

The BCM is involved in the A/C operation. Sunlight sensor, Outside air temp sensor, ETC.

If the compressor is running and it is not very cold it could be a TXV. But since you state the compressor cycles off, one or more sensors are involved. A scan tool might give you a way to test the sensor operations.

Could also be a blend door servo. Calibrating the servos and making sure they work is another scan tool job...

I got to work on this truck again this morning. A previous owner had already tried to add a resister to the temp sensor going to the evaporator. The resister was only plugged in on one side. Plugged it in and the performance didn’t change. I added 356k of resistance. Vent temp got down to 45 on the road. Added another 40k. The owner is going to try it and see how it does.

The original resister was 200k.

Good info, please let us know how this works out and the total ohms you end up with; this will help the next guy

This truck was back again. Same problem. Vent temps just aren’t cool enough. Recovered the charge and I had it 6oz overcharged. Changed the expansion block while the system was open just to eliminate that. Vacuumed and recharged by weight. Performance didn’t change. This truck has electric fans. My question is, does the performance of electric fans diminish as the wear out? I will admit that I didn’t confirm that both fans were running. It made such a loud sound when the fans ran it sounded like a plane taking off. I will follow up on that.