Car AC problem/symptom and question

[wh500special 2,413]

The AC in my ~2010 Ford Edge started blowing warm air this spring. I like driving with the windows open so chose to ignore it, but now my daughter is home from college and using the car so there’s motivation to do something about it. 
 

Last summer it did the same thing so I took it to a local (very competent) shop who sucked it out, checked for leaks, recharged the 134A to spec, and tested it.   That seemed to fix it for the most part, but periodically it would blow hot for a while then clear up and cool reasonably well.  So something was wrong that was only showing up periodically and not when they had it.  
 

They indicated it was actually overcharged quite a bit when they started messing with it, so it must have a history with a prior owner not getting hood cooling from it. 

 

For the last couple weeks I told my kid just not to use it and I’d look at it eventually.  Today was eventually. 

 

With the engine running and the AC running wide open in my 85 degree garage I am getting around 25 psi on the low side and about 325-350 psi on the high side.  At idle.  That seems high on the high side. Compressor stays on and isn’t kicking off due to overpressure, so maybe this is normal but it seems higher than most references call for. 
 

Revving the engine to 1500 RPM dropped the low side to 11 psi and increased the high to about 400psi.
 

I get cool air out of the vents, but not cold.  Measured 52F-55F using outside air (not recirc).  In the sun with the greenhouse this car has, that’s not really adequate to do much useful cooling. 
 

To see what happened and get another datapoint, I trickled in a little additional refrigerant and the dash temperature rose and the pressures went up a little bit (55F-60F/30psi/350-370psi). That suggested to me that I was going the wrong way so I called it quits there. I considered bleeding some out to get another datapoint, but i wanted to be able to sleep tonight.  
 

I did read that this particular car is pretty sensitive to refrigerant charge, so it could be off.  But adding up other factors (previously overfill, sporadic operation, etc) suggests it’s something else too. 
 

I watched the gauges when I shut the engine off, expecting to see the high and low sides equalize.   After about 15 minutes the low side was in the 100 psi range and the high was still above 200.   I may check it in the morning to see if they do eventually equalize.  I assume there’s nothing deliberate in the system to keep the fluid from moving around. 
 

I’m not an AC person, but this kind of smells like an expansion valve problem to me.  
 

It’s a cheap part ( <$50 ), doesn’t look too hard to get to, and I can borrow a recovery unit and vacuum pump from work so this is doable in my driveway for minimal cost.  But if those of you who know things think the valve is a low probability for its ailments, I can go back to my strategy of just opening the windows.
 

I guess it could be the filter too/instead, but the wide delta when the system is off probably is a clue. Evaporator could be clogged, but taking the dashboard out to get to it is not on my list of things I will do.  

Any thoughts on whether I’m on a reasonable path with the valve?

 

thanks,

Steve

 

 

[Blaine 26]

Your pressures suggest a restriction, a new expansion valve is where i would start. Sounds like it’s sticking. Being that the high side is well over 300, the compressor appears to be in good shape, or at least capable of making good pressure.

 

  I would still inspect the high side of the expansion valve for compressor debris which may have got caught at the expansion valve and has caused the restriction. 
 

  Sometimes you can hear a sticking expansion valve if you listen closely to the dash, idle up to around 1500rpm, and a lower blower speed so you can hear over top of it.
 

 Silent for a few seconds, then a few seconds of hissing in the dash accompanied with a brief gush of cooler air through the vents, then back to warm, and the cycle repeats. Yours sounds to be just stuck. 
 

 On the newer (i’m old so everything is newer now) small capacity systems, it can be rather easy to flood the evaporator with just a few ounces of being overcharged, so be careful not to overcharge it, and check or just replace the cabin air filter if you haven’t already. They are often overlooked. 

[squonk 46,842]

I used to have my own auto AC shop and did it for many years at dealers before that. It is either the expansion valve or the overcharge condition. Since this car has been messed with I would replace the valve I would also consider replacing the condenser as the receiver drier is part of it as as an assembly.

 

But here is one thing I would insist upon. Whoever recharges is I would insist on evacuating ( running the vacuum pump) for at least 2 hours. Many shops have AC machines that run the pump for 30 minutes and kick off. On a system that has leaked or been messed with there is no telling how much moisture has gotten in it. Water gets trapped in the refrigerant oil and you have to boil that moisture off and it can take quite a bit of time for the water vapor to break out of the oil and get sucked out by the pump. I made good money from customers who had their car at a shop ( mostly body shops) and the AC would work on and off or not get real cold. All it took was to run the pump a few hours and recharge it.

 

It even happened to me after I didn't have my shop anymore. My wife had a Toyota van. The rear AC line failed so I took it to a shop that specializes in Toyota's and they replaced the line and recharged it. It worked for a day and a half. I suspected air and moisture in the system or a piece of dirt got into the expansion valve, I asked before they replaced the valve they recover the refrigerant and run the vacuum pump all morning and recharge after lunch. That fixed the issue. No parts required. I'm including a short video of my findings on my gauges the morning after it quit working after the line repair.

 

 

Edited 7 hours ago by squonk

[953 nut 66,566]

7 hours ago, wh500special said:

periodically it would blow hot for a while then clear up and cool reasonably well.  So something was wrong that was only showing up periodically and not when they had it.  

Had the same problem on my wife's Ford product. The damper that controls the airflow (defrost, heat, cooling) has a default position of defrost with heat. It is operated by vacuum and the bean counters at Ford decided that a small check valve on the vacuum line to the comfort control system would work as well as a vacuum reservoir. If the check valve isn't functioning properly when you accelerate rapidly or go up a steep hill the vacuum produced by the engine reduces to the point that the damper previously mentioned goes to the heat / defrost default position until vacuum is restlored.

We had the wife's car to two Ford dealers who tested everything in the refrigerant system but didn't know a thing about the vacuum problem, the good old boy who services our vehicles knew exactly what the problem was when I asked him and once the check valve was replaced the problem went away.

[squonk 46,842]

Pressures are wrong. Too low on the low side and too high on the high side. Should be in the 35lb/ 200lb range Not a damper issue

Edited 5 hours ago by squonk

[953 nut 66,566]

25 minutes ago, squonk said:

Not a damper issue

9 hours ago, wh500special said:

periodically it would blow hot for a while       

9 hours ago, wh500special said:

So something was wrong that was only showing up periodically and not when they had it.  

 

Mike, the key word here is periodically. He didn't indicate any regularity of these occurrences like you might expect from an expansion valve.       

[squonk 46,842]

49 minutes ago, 953 nut said:

Mike, the key word here is periodically. He didn't indicate any regularity of these occurrences like you might expect from an expansion valve.       

A sticking expansion valve would certainly cause these issues. Low suction and high discharge. And some days it works and other days it doesn't. An expansion valve that has lost it's sensing charge would fail and stay failed. 

 

The most common "periodic " loss of cooling I've run across is air/moisture in the system causing evaporator freeze up or freeze up at the point of expansion. Air/ moisture at the point of expansion  would cause the expansion valve to stick and then start working again when it thaws out. Seen it dozens of times. 

[953 nut 66,566]

6 minutes ago, squonk said:

start working again when it thaws out

 

10 hours ago, wh500special said:

Last summer it did the same thing so I took it to a local (very competent) shop who sucked it out, checked for leaks, recharged the 134A to spec, and tested it.   That seemed to fix it for the most part, but periodically it would blow hot for a while then clear up and cool reasonably well.  So something was wrong that was only showing up periodically and not when they had it.  

No doubt about the freezing and thawing, but wouldn't  you think that would have come up when the AC shop was testing it?   Just because you haven't experienced the vacuum damper problem yourself is no reason to not give a bit of consideration too. 

[wh500special 2,413]

2 hours ago, 953 nut said:

Had the same problem on my wife's Ford product. The damper that controls the airflow (defrost, heat, cooling) has a default position of defrost with heat. It is operated by vacuum and the bean counters at Ford decided that a small check valve on the vacuum line to the comfort control system would work as well as a vacuum reservoir. If the check valve isn't functioning properly when you accelerate rapidly or go up a steep hill the vacuum produced by the engine reduces to the point that the damper previously mentioned goes to the heat / defrost default position until vacuum is restlored.

We had the wife's car to two Ford dealers who tested everything in the refrigerant system but didn't know a thing about the vacuum problem, the good old boy who services our vehicles knew exactly what the problem was when I asked him and once the check valve was replaced the problem went away.

The car actually has either this problem or

Something similar too.  This has the electronic control that allows the driver and passenger to set their own temperatures.  Most of the time the driver’s side doesn’t get back to the full

cold position so the temperatures aren’t even.  I was attributing it to the little electric actuator not working properly, but maybe it’s a vacuum issue.  
 

Thanks for pointing this out!

steve

[squonk 46,842]

1 minute ago, 953 nut said:

 

No doubt about the freezing and thawing, but wouldn't  you think that would have come up when the AC shop was testing it?   Just because you haven't experienced the vacuum damper problem yourself is no reason to not give a bit of consideration too. 

I have seen the damper issue plenty of times. But the damper won't effect the pressures. Especially the high side. 

[wh500special 2,413]

Thanks guys.  Sounds like the general consensus is probably the expansion valve.  I’ll tear into it at some point and hopefully that’s the whole of it. 
 

Our former AC guy at work would put the vacuum pump on our big systems and run them all day and sometimes overnight before recharging.  He was big into pulling out all the moisture.   Easy enough to do, so we’ll do that.

 

THANK YOU all!

steve

[squonk 46,842]

Just now, wh500special said:

The car actually has either this problem or

Something similar too.  This has the electronic control that allows the driver and passenger to set their own temperatures.  Most of the time the driver’s side doesn’t get back to the full

cold position so the temperatures aren’t even.  I was attributing it to the little electric actuator not working properly, but maybe it’s a vacuum issue.  
 

Thanks for pointing this out!

steve

Depending on the car design and the location of the evap on the fire wall. If it's a low charge or restricted flow, the side the refrigerant enters the evap will be cooler than the opposite side. This happened on my wife's Toyota van. The charge got low from the unknown rear line leak and the air coming out of the outlets was cold on one side of the car and semi cool on the other side.

[squonk 46,842]

5 minutes ago, wh500special said:

Thanks guys.  Sounds like the general consensus is probably the expansion valve.  I’ll tear into it at some point and hopefully that’s the whole of it. 
 

Our former AC guy at work would put the vacuum pump on our big systems and run them all day and sometimes overnight before recharging.  He was big into pulling out all the moisture.   Easy enough to do, so we’ll do that.

 

THANK YOU all!

steve

I redid a couple 200 lb . Systems. 2 vacuum pumps running for a week with daily oil changes.

[squonk 46,842]

Another scenario is your 325 psi is pushing 165 degrees condensing temp. Way to high. It would have to be 130-140 outside to even get close to that under a normal system. The high pressure cut out may be turning the compressor off.