AC Not Blowing As Cold

[jtupp72]

2016 F250 seems to be not blowing as cold as it should. Hooked up some gauges and here are the readings with windows down and max AC.

Low - 37
High - 215
94°
70% RH

Being a 7 yr old vehicle, I suspect it mat be a tad low on refrigerant, but I don't know how to read the numbers. I have a cheap laser thermometer reading about 54° at the center vent, but with windows up. It reads much higher with windows down, but I think its reading the ambient air as well.

[Cornbinder89]

Your low side shows an evap temp of 42 deg so no wonder it doesn't feel as cool
138 or there abouts for condensing temp, a little high but still in the ball park of 30-40 deg above ambient.
Pressures can only tell how well the system is moving heat, not if it is properly charged.
I'd have to check, but this is a CCOT system isn't it? If so is the compressor cycling or running all the time?
The temps given are the temp of the refrigerant not the air. The refrigerant has to absorb the heat from the condenser coil which has to absorb from the air passing through, 54 is a bit higher than I would expect 42 deg refrigerant to cool the air too.

[Cornbinder89]

Ok, went and looked (rockauto to the rescue) it is a Tx system, so the compressor shouldn't cycle, or at least not often.
1st thing I would look to is air flow over the condenser. Also condenser condition. If the fan clutch or electric fans aren't moving enough air, or the condenser is degraded in any way, the heat will remain and cycle back to the evap.
You can try spraying water on the condenser and observe the pressures/temps while the condenser is "water cooled"

[jtupp72]

Ok, went and looked (rockauto to the rescue) it is a Tx system, so the compressor shouldn't cycle, or at least not often.
1st thing I would look to is air flow over the condenser. Also condenser condition. If the fan clutch or electric fans aren't moving enough air, or the condenser is degraded in any way, the heat will remain and cycle back to the evap.
You can try spraying water on the condenser and observe the pressures/temps while the condenser is "water cooled"

Please forgive my ignorance. I assume Tx is thermal expansion?

So inspect condenser and spray water on it while running AC? What should I be looking for? Also, FWIW, the temp reading was taken with windows up on max AC at 1500 RPM. Don't know if that matters or not.

On another note, maybe related...I've also noticed that the air flow out of the vents doesn't deem to be as high either. A common issue with these is the evaporator getting clogged with dust since there is no cabin filter. There is a hack i found online where you can cut into the evap box behind the glove box and get access to the evap coil. I did that and took the compressor and sprayed air into the coil, then sprayed it good with a water hose. I see no difference in air volume whatsoever.

[Cornbinder89]

Yes, Tx is shorthand for Thermal expansion valve.
Spraying water on the condenser while the system is on is a short-cut that makes it temporarily better at removing the heat. If both high and low drop and the outlet air cools, it is an indication that not enough heat is being lost at the condenser. If you run the test, you will always see some drop, but if it suddenly cools like it should, and you see low side pressure in the mid 20's, you have found the source of the warm air, and you have to dig a little deeper to find out why the condenser isn't loosing heat. could be air flow, could be bond between fin and tube or could be some tubes are restricted. It could even be that the condenser size (by the mfg) is marginal to begin with, and heat, humidity and age make it not up to the job. If , however the high side drops and the low side stays high, it could indicate a low charge, but there may be more to it. With you high side already at or slightly above the expected high side pressure, adding more will make that worse, so likely even if it is low, there is another problem also, again likely at the condenser
The same thing you did at the evaporator, checking for air flow through and obstructions in the condenser should be done. Make sure the fins aren't damaged and the engine fan (s) are working. A bad fan clutch or one that is slipping at low speed can cause you problem.
I know Fords in the 90's had a problem with this, the fan wouldn't pull enough air at idle once they got some miles on them, and the A/C would suffer, in those cases, the a/c would do better at highway speeds but around town would be warm. A new fan clutch was the solution. Not saying it is in your case, just that it is something to check.
It is still possible that the amount of refrigerant is off, but the only way to be sure is to suck it all out and re fill by weight. Because your pressures are not way out of the ball park, and you have higher pressure, it isn't where I would go first.
I would start with the checks (water on condenser, visual of condenser, and air flow) that don't cost anything.
Air flow can be tricky. changes to the front of the truck or removal of air-dams below can effect air flow through the condenser and rad. same with fan shroud in the engine compartment.

[jtupp72]

Got home today and took a look at the condenser. I can't see anything out of the ordinary and the fan is running like it's supposed to as far as I can tell. Admittedly, seeing much is next to impossible the way they have that 6.7 shoehorned in there.

I hooked up the gauges again and took pics before and after spraying the condenser down. Not much drop on the low side, but quite a bit on the high side. The temp was 97 with 60% RH. The vent temp dropped from 54 down to about 47.

Before spraying condenser:


After spraying:

[Cornbinder89]

Looks like you low side went from 42 to 39, so not much change. Your condensing temp dropped to 110 deg. Without the water, feel the inlet (from the compressor), the condenser and outlet pipe, temp should drop consistently as the refrigerant passes though the condenser. If it seams even, it might be time to evacuate and recharge by weight.
I fear that if the system is low, and more is added, you'll see the high side go up as well.
In the old days, if the fan clutch was working on a hot day with the A/C on, you would hear a roar at 1500 rpm if it was working and it would be fairly quiet if it was slipping.
If you are going to have to pay for a recharge, there is not much to loose by adding a little refrigerant a little at a time and watch what happens to the pressures.
If the system was messed with before and not evacuated properly, I would suspect some air in the system, this raises pressures across the board. You didn't mention being worked on before the trouble started.
If you take the chance on adding, do so a little at a time and let the system stabilize pressure before adding a bit more. If the high side starts to rise a lot, stop! Too much ends up as liquid in the condenser, reducing the area available to condense the hot gas and pressures will spike.
Going back to the beginning, this system had been working well in the past, and has deteriorated over time, and no work has been done until now? is that correct?

[jtupp72]

Going back to the beginning, this system had been working well in the past, and has deteriorated over time, and no work has been done until now? is that correct?

As far as I know, yes. The truck was 3 years old when I bought it. I've put almost 100k on it and the AC has worked fine until recently. Some days it seems to work better than others and, obviously, it works well at night. The system hasn't been touched since I've owned it.

How do I add refrigerant without introducing air into the system?

[Cornbinder89]

Generally it isn't a problem, either the line is purged when hooking to a tank, or enough leaks when first connected to force the air out of the line before it enters the system. I always try and shoot a little out of the line before connecting.

[jtupp72]

Okay, so again forgive my ignorance. Walking through what I remember, I add as gas through low side? So, low side hooked up and yellow hooked up to the refrigerant, then open the low side valve to suck in refrigerant, correct?

[Cornbinder89]

Yep. but before you do that, when you hook the yellow line to the refrigerant, crack the yellow line loose at the gauges to purge the air out of the line, Just loosen a bit until you get a bit of "frost" from the escaping refrigerant.

[Cusser]

How do I add refrigerant without introducing air into the system?

First: avoid any sealers or any cans of refrigerant that contain sealers. That includes most cans that are sold with a dinky hose and gauge.

Read about purging or burping the air out of the hose to the low pressure side with a little refrigerant from the can before opening the valve at the vehicle end. There should also be Youtube videos that show this.

Many locations of Autozone have loaner R134a gauge sets.

[Tom Greenleaf]

Thanks Cusser.

OP, you fill into a vacuum = nothing is there. No air, so no moisture is moot.
It's a trade of it's own that isn't so DIY friendly. Yes you can AYOR you can ruin a system in no time flat.

Hate to post links (is like cheating) this spot has the people, info I can't even search it here??

I put a lot at another can read it without being in some club it was to be open to read a real mess by me collected from archives now over 20 years the info still stands.

Click here >> http://autoforums.carjunky.com/Autom...YSTEMS_P45460/ <

I know I failed to organize that better charts are there one thing I know isn't is a trick if a car/truck has a high side port - I think this does?

While under full vacuum with gauges locked down, hose to source of PURE product add thru high port till gauges read just a bit on the plus side. Now you almost can't add the air.

Purge hoses where used the newer EPA (so called) ones just push enough on a port to spit thru the hoses.

Good to now. Been plain decades now I use blank retrofit ports not used EPA hose will spit then take those out.

It's a trade you learn to do with what you have as just said can borrow some stuff at chain outlets for 100% deposit for safe return. Up to you to buy some things you really need to own was costly is worse now.

It's doable. Stop when it isn't working out find out why right away,

[jtupp72]

I really appreciate the input guys.

I added maybe 1/2 can of refrigerant and the high side pressure climbed about 25 psi so I quit. It started at about 225 and got up to about 250 at idle. Below are pics of the pressures at idle and at 1500 rpm. Temp was 97° with 50% RH. I got the center vent temp down to about 48° at 1500 rpm. So is this acceptable or should I do something else?

***EDIT - following the link that Tom Greenleaf posted, 97° multiplied by 2.3 would give me 223 psi so it would appear that I'm about 25 psi high. Is this a concern?

[Tom Greenleaf]

Insert of all things you must know REAL temps? 25# something doesn't mean exact the temp of any freaking thing is where is at the time then it counts.

I use "in-out" thermos like toss end out a kitchen window beat other things were dirt bucks needed to know.

Infrared doesn't read properly or at all if not on hard surface. Know your equipment.

Know the performance inside. Constantly monitored or no point?

[jtupp72]

Insert of all things you must know REAL temps? 25# something doesn't mean exact the temp of any freaking thing is where is at the time then it counts.

I use "in-out" thermos like toss end out a kitchen window beat other things were dirt bucks needed to know.

Infrared doesn't read properly or at all if not on hard surface. Know your equipment.

Know the performance inside. Constantly monitored or no point?

Appreciate the input but I'm not sure I follow. The ambient temp i posted was the actual temp at the time the gauges were read. Before adding any refrigerant, the high side was reading 225. It got up to 250 and I stopped adding refrigerant following Cornbinder89's advice below.

If you take the chance on adding, do so a little at a time and let the system stabilize pressure before adding a bit more. If the high side starts to rise a lot, stop! Too much ends up as liquid in the condenser, reducing the area available to condense the hot gas and pressures will spike.

[Cornbinder89]

250 is 148 deg F or there abouts for condensing temp. I'd stop there. If you go past the mark, you'll just make cooling worse. The temp/press chart for R12 and R134a is here:

https://forum.aircondition.com/forum/reference-and-resources/111-r-134a-vs-r12-temp-pressure-chart

Your other option is to have it all sucked out and re charged by weight.
Adding to a charged system is always a crap-shoot. You can't charge to a set reading on the gauge and say it is right. The gauges only tell how well the system is moving heat.
If you had an oversize condenser and a large receiver, exact charge becomes less critical. As stock, is often "just big enough" getting the charge correct is more important.
You have made a difference in the positive direction, and are staying just outside the desired 30 to 40 deg over ambient temp range for condensing temp. That 30-40 deg assumes your ambient reading is in fact what is passing through the condenser, and no hot air is bouncing off the pavement and being re-cycled through the condenser.
If you find this is not "good enough" then I would go for the recharge by weight. Just my 2 cents worth.

[Cornbinder89]

P.S. your low side is just about spot on. 33 degF

[jtupp72]

Thanks again for all of the help. With forecast highs around 100°+ for the next week, I should be able to get a good read on performance.

[jtupp72]

Well, I went and ran a couple of errands and it appears to be performing worse now. Granted, it's 101° right now, but it's definitely not cooling as well. I'm going to find a shop to evacuate a recharge by weight as suggested.