A/C not performing well in hot weather after all new parts and recharge

[AGrayson84]

Hi everyone, I bought a 2006 Navigator a little over a year ago, and when summer came around I noticed the A/C system performed poorly, especially while at a stop. If I drove down the highway without stopping for 35+ minutes, with the A/C on full blast (coolest temp setting on front and rear A/C systems, fastest blower speeds, recirc mode) I could eventually see 45 degrees coming out of the dash vents on an 80-some degree day. As soon as I'd slow down to 15 MPH or less, I could watch the outlet temp start increasing. Not rapidly, but after 6-10 minutes of having slowed down, I could see a 10 degree increase in temperature.

I'm going to cut out a lot of stuff that I did to the A/C system since last summer, because I replaced a bunch of parts and had no better luck. Cutting to last month, I have replaced the following with brand new Motorcraft parts:

Compressor, condenser, filter/drier, muffler, both expansion valves, both evaporators, all o-rings, fan clutch and fan blade assembly, heater valve, both front blend door actuators, rear blend door actuator.

Literally all lines under the hood were new. The only thing I have not replaced in this entire endeavor is the set of lines (suction and discharge), but they have been thoroughly flushed and dried with dry air. No debris or anything whatsoever was found in those lines except clean PAG oil. All new parts were then installed, 14 oz of PAG oil added to the compressor, 1 hour vacuum was done using a 6 CFM vacuum pump, after 30 minutes there was no vacuum loss and then system was then filled with a Snap-On A/C machine. 3.6 lbs of R134A was added. Everything has been done 100% to the book, twice now. But the A/C system continues to refuse to cool below 45 degrees on the highway, and continues to perform poorly for an extended time while driving down the highway.

I even went to the length of adding two, high-velocity, 12" electric puller fans directly attached to the back side of the condenser, thinking the condenser was getting not cooling well enough. It has helped bring the high side pressures down some, but has not offered a noticeable/worthy drop in outlet temperature.

My family owned a '98 Expedition from 2000 thru 2013. Never once serviced the A/C since new, and it never struggled to cool at idle, and blew 39-40 degrees out the vents without effort. This Navigator continues to take forever to cool no matter what I have tried.

Last week, we had a 98 degree day here in Maryland. I had a nice Covercraft windshield shade secured behind the windshield (these keep out a bit of heat compared to flimsy things you get at Walmart or the parts store), and my front windows are tinted to match the rear windows. So though it was hot outside, it wasn't exactly baking inside the car. I fired it up and let both A/C systems run full blast for 15 minutes. Got in the car and the outlet temp was 71 degrees. The car was still pretty warm on the inside, as 71 degrees coming out the vents doesn't cool as well as one might think in the hot sun. I drove the car for about 4 minutes to make it to the highway, and before hitting stop-and-go traffic, the outlet temp had gotten down to 63 degrees. Still not very cool, but did better now that I was moving. After about 8 minutes of being stuck moving from 0 to 10 MPH, the temp increased to 73 out the vents. A full 45-50 minutes after I started the engine, with the A/C systems STILL at full-blast, I was still crawling in traffic with only a 71-74 degree outlet temp. The car was still pretty warm.

Once I finally was able to pick up speed down the highway for a about 15 minutes I had gotten down to around 52 degrees outlet temp. This system is just struggling for some reason. I've owned 8 Fords since 2004, and not one of them has ever had a problem achieving 40 degrees or less out of the vents, especially when moving. Sitting still, I think 42 has been the warmest outlet temperature I've seen on any of my past Fords on a hot day. This one won't possibly below 70 sitting still on a hot day.

Even in inside my buddy's shop that was 72 degrees ambient temperature.... when we filled the A/C system to the 3.6 lbs, it still wouldn't get lower than low 50's coming out of the vents. We've clamped off both ends of the heater core and nothing improves. The rear system blows just about the same temperature as the front.... so it's not isolated to just one of the two systems.

What gives??? Nothing adds up here. The compressor isn't short-cycling, and nothing else seems to be acting up. When driving down the road on Sunday afternoon, it was 84 degrees out and I routed my R134A manifold gauge set thru the passenger's side window so my friend could monitor the pressures while driving. Low side was 25 PSI and high side was 196 PSI, and this was after 40 minutes of the A/C system running at full-blast.

Anyone with any solid suggestions would be really highly appreciated! At this point I have given up on it, but then every hot day while I sit in the car nearly sweating reminds me that I can't allow myself to have spent all of this time and money on parts and still be dealing with a hot cabin.

-Andrew

 

[stamp11127]

Do you hear a change in the high fan speed between max ac and fresh air ac? Max ac sounds like more air is moving through the system.

What are the pressures a couple of minutes after running at idle in the shop?

The pressure readings after running a long time are within spec so look at the airflow in the system. Any condensate on the front evap line or dripping from the plenum box.?

Do a redneck system test - put your hand on the low side line while running. If it is "damn that's cold" it's good. If it is cool there may be too much refrigerant going into the evap.

Since you have access to the snap on machine I'm going to assume it will reclaim. Reclaim it, note how much oil is removed. Recharge with 70% of recommended oil and 80% of recommended 134a. Run system and let it stabilize - note pressure and temps. Add if refrigerant if needed.

 

[AGrayson84]

Hi Stamp, thanks so much for the helpful response! I've honestly been struggling to find someone that can help me with this.

I definitely hear the isolation door shut, and hear what sounds like the fan speed up some, and definitely hear the air flowing in the plenum noticeably louder when going from fresh air to recirc/max ac. I also inspected the foam on the isolation door and confirmed it is sealing off properly.

The low pressure lines that run from the back side of the engine bay to the front are definitely full of condensation. The front a/c suction line as more condensation that the rear a/c line under the hood, but I suspect that is due to the much longer length of the line that runs to the rear system. I'll have to check tomorrow and see if it's quite, "damn that's cold". I can put my infrared thermometer on it too and see what it is reading. I do recall it being pretty old last time I touched it, after the system had been running for a good bit of time. Otherwise, if I fire the system up in warm weather, the lines take some time to get cold and start sweating. Definitely no frost on any of the lines, as far as I can see, which is good (we know that frost = possible blockage sometimes). Condensation is rolling out of both evaporator plenums at a pretty good rate one hotter days. Definitely no blockage in the plenum nor condensate drain. I opened and thoroughly inspected both plenums, and even cleaned the minor dust in them from the past 11 years. Both evaporators were extremely clean... almost like new. I initially though for sure that I'd find dirty, clogged evaporators when I went to replace them and everything else.

The Snap-On machine will definitely do a reclaim. We've reclaimed the system twice so far, both times running a 1 hour+ vacuum on the system before re-charging to spec. Unfortunately, my buddy with the machine is an hour away and because of my work schedule I can only make it out there to visit his shop every other Friday when I'm off work, so doing another reclaim won't be as easy as just pulling it into my garage unfortunately.

But if it helps, we've charged the system from completely empty twice now after I installed all new parts. One time the vacuum was even ran for several hours to remove any possible moisture. But both of those times there was definitely absolutely no refrigerant in the system since everything was new, and we filled with the exact 3.6 lbs per the requirement on the truck. So that's filling the system 2 times from scratch, and doing a recover/vacuum/recharge two separate times. We've tried adding .2 lbs more refrigerant and .2 lbs less refrigerant, and no change.

I can surely try to get him to recharge with just 70% of PAG oil and 80% of R134A... I just fear it won't help from what we've done so far.

By the way, when it was 84 degrees ambient temp on Sunday, the static pressure on high and low was around 92 PSI. Pressure was fully equalized (car sat for 14 hours without running), and the car was in the shade that entire morning when I checked, so the engine bay was also around 84 degrees. Figured I'd give the static pressure in case that helped. Thanks again Stamp!

 

[stamp11127]

You should see lower pressures with the 80% charge but not a drastic difference in the vent temps. I'm curious about the amount of oil recovered this round. I would like to know the pressures after 1, 2 & 3 minutes of running at idle. You should have a low side pressure around 35psi.

What you are describing sounds like a mixture of conditioned air and unconditioned air mixing resulting in warm air coming out of the vents. I'll look at the airflow diagrams tomorrow after work.

 

[docraymund]

Your low side pressure reading is low coupled with the fact that the suction line is very cold to the touch indicating that less refrigerant is entering the evaporator. You need to add some more. Also check the air gap on the conpressor.

 

[AGrayson84]

You should see lower pressures with the 80% charge but not a drastic difference in the vent temps. I'm curious about the amount of oil recovered this round. I would like to know the pressures after 1, 2 & 3 minutes of running at idle. You should have a low side pressure around 35psi.

What you are describing sounds like a mixture of conditioned air and unconditioned air mixing resulting in warm air coming out of the vents. I'll look at the airflow diagrams tomorrow after work.

Thanks again Stamp. I'm not aware of how much PAG oil was recovered the last time, but I just know that he added back the exact amount that was recovered.

So specifically, you'd like to know those pressures 1 thru 3 minutes of running for the first time, AFTER then engine has completely cooled down overnight or something? If so I can definitely do that. I can take a nice, clear video of the gauges and link it in here. Might not be able to do that until Friday or Saturday though.

And I agree-- it does sound like a mixture of heat coming off the heat exchanger and/or coming in from the cowl (outside air), but of course everything I have done and have checked eliminates that from the equation. And when I clamped off both lines of the heat exchanger to heat exchanger side of the lines were completely cool, whereas the engine side of those lines were hotter than hell. Isolation door is without a doubt not letting in any outside air.

This morning it was about 77 degrees outside and I was able to pull 45-46 outlet temperature going down the highway after a few minutes of driving. The compressor will cycle off when I get to that low of outlet temperature while going down the highway, so I plan on doing the resistor mod to prevent the compressor from cycling that soon, and perhaps get the outlet temp down to 40 degrees or so with the right resistor-- but the compressor does not cycle off when it is hotter outside and the system is struggling to cool the car down. I have monitored all of this using FORscan on several occasions.

I pulled into the parking lot at working this morning with 46 degrees on the vents, so quickly parked and opened the hood. The front evaporator suction line was definitely chilly. Not too cold to keep my hand wrapped around, but definitely chilly. Plenty of condensation. I wouldn't necessarily say "damn, that's cold"

Your low side pressure reading is low coupled with the fact that the suction line is very cold to the touch indicating that less refrigerant is entering the evaporator. You need to add some more. Also check the air gap on the conpressor.

Thanks for the response doc! I've had a few other people tell me my low side is within spec, but I personally felt it was a little low according to the standard R134a ambient temperature and pressure charts I've seen. Those charts say I should be at 45-55 PSI, but many people and other data seems to say that 25 PSI was normal, so I'm really torn.

I may have been wrong about the suction line being very cold. I'll have to check it over the next few days a little more frequently, but as I just mentioned to Stamp, it was 77 degrees this morning and my outlet temp was 45-46 degrees, and the suction line from the front evaporator was only chilly, if I had to describe it. Not very cold. I'll see how it is over the next few days, at different ambient temperatures, and try to get an actual reading of the temperature of the line.

We have tried adding .2 lbs over the factory fill of 3.6 lbs, and outlet temperature actually increased some. The compressor is brand new, but what exactly do you suspect I should look for regarding the air gap on the clutch?


Thanks again!!

-andrew

 

[stamp11127]

At 77 degrees this morning it should have chased you out of the cabin.

One of the nice things about r134a is the pressures are very close to the air temp leaving the evap or condenser. If you have a low side of 40 then you can expect a least 40 degree air entering the plenum after the evap. As you increase rpms on the engine the compressor works more efficiently and changes the pressures. We normally see the upper 20's on the low side at rpms above idle. The lower 20's do concern us though and we evaluate if more refrigerant is needed.
Lower low side pressure can come from a under charge or a slight blockage between the compressor and evap. If there is a restriction you may see a slightly higher high side since that side tends to "load up".

The pressures when the system first starts after stabilizing over night are what I'm looking for. Some times the low side will increase in pressure then drop into range within the 3 minutes. Other times it will drop below the lower threshold and cycle the compressor until it runs a few minutes. So basically what is this bad boy doing at startup? A video as you suggested would be great.

 

[AGrayson84]

Yeah, that's my thought too. Shouldn't take much at that low of an ambient temp to get that outlet temp really cool.

I seriously can't imagine a restriction at this point. All lines and components through the entire A/C system (except the lines that run from the engine bay to the rear system) have been replaced twice. Originally I used some aftermarket parts (Four Seasons) and thinking something was at fault there and not wanting to keep evacuating, replacing parts one at a time, and charging the system again, and keep trying... I just went and ordered all Motorcraft stuff this time around. The lines that weren't replaced, the rear lines, have been flushed multiple times and never had any problems blowing through the lines. Never found any debris in those lines either... just clean PAG oil. And after two filter/drier assemblies, if there WAS debris in the system somehow, you would think that the previous replacement filter/drier would have collected it all. So I'm pretty confident in thinking that there is no restriction with all of that said. Still could be wrong, somehow. Like if some dirt bag at Amazon was pouring sand into the new parts before shipping lol.

I'll get you some video of exactly what you want this weekend, and I'll try to get an accurate reading of the front and rear evaporator temps. I read 70 degrees on the rear evaporator lines, just behind the TXV, with my infrared thermometer today. Might be a fluke, because the aluminum might be reflecting the reading from the gun. I have a friend with clamps that read temperatures that he uses for his residential and commercial A/C work... I'll see if we can't try with those this weekend. Thanks again Stamp!

 

[stamp11127]

I took a quick look at the service DVD and of course they have very little on the automatic temp control in the Navis. I'll try to look at the Expedition tonight and hopefully they will have a diagram we can look at.

I'm dealing with my second "4 legged family" death now so I'll be lost for a while.

 

[jeff kushner]

I took a quick look at the service DVD and of course they have very little on the automatic temp control in the Navis. I'll try to look at the Expedition tonight and hopefully they will have a diagram we can look at.

I'm dealing with my second "4 legged family" death now so I'll be lost for a while.

Sorry to hear Stamp....you help a lot of people hear and losing a member of the family, 2 or 4 legged can be rough...especially for the kids & whoever was closest.

jeff