Truck AC issues.

I've been having issues with the truck AC since October. Compressor and Accumulator have been replaced in the past couple of years. I bought an infrared thermometer to provide the AC folks with some data. AC starts off cold. 48 degrees coming out of the duct. Running down the highway an hour and it is now 68 degrees coming out of the duct. Another half hour and it is 78 degrees. A half hour later 88 degrees. Shut off the AC and drive a half hour, and start the AC and it's back to cooling at about 68 degrees. I think the compressor is freezing up. If so, why? What say the TFF?

Maybe the condenser is clogged with dirt/grime/debris? What kind of vehicle is it? I know on some of the Ford Super Dutys that if they are used offroad in dirty dusty condition the evaporator core inside the a/c case can become clogged as well. Id check that first.

Dodge 6.7 Cummins Mega Cab 4WD. Not operated in a real dusty environment though.

It won't freeze with 48 degree air. It's broke again. The air should get colder but stay at about 40.

Not sure if it is involved in the air flow to the cooling system componets or if it just filters the air coming into the cabin, but have you checked to see if your truck has a cabin filter? and has it been changed?

I changed the one on my last car at 100k for the first time and I'm amazed air even came out the vents that thing was so filthy. Just an idea to check, I have no idea if it could really be the problem or not.

Have no idea about the Dodge but the Ford trucks I have had in the past had an orifice tube in the line that would clog up, especially after a compressor failure/replacement, changed it out and had cold air again.

I don't know what Toyota does different but I have had my Tundra for 10 years and it still blows cold as day 1 and I've never done a thing to it.

The tube was the last thing that was replaced. It was clogged, but obviously not the real problem.

fist thing you need is pressure reading at idle with a/c on max with driver window down, then a reading at truck idling at around 2-2,300 rpm you can use a stick. Could be low charge, accumulator went bad. It doesn't matter what environment you drive in I have stuff come in here at the house looks clean but you remove the top plastic cover and start blowing stuff out you would be surprised at the [censored] that comes out of the radiator, charge air cooler and a/c condenser. All 3 of those things need to be clean in order to achieve maximum air flow across the a/c condenser.

Have you checked the blend door operation? Maybe it's opening up slowly and letting hot air in.

what he said.

Why was the compressor replaced? If it went out catastrophically, then the actual recommendation is to replace the condenser too. This is because the condenser lines on the newer vehicles are too small to flush out and debris can and will get trapped in there causing cooling issues.
On my truck, the evaporator coil under the dash was dirty and it stopped blowing cold because it was freezing up due to moisture buildup in the dirt and grime. Basically the dirt and grime prevented the moisture to condense and drain away and it caused freezing on the surface. I had to pull the dash and replace it. I'm a DIYer and it took me 3 hours start to finish to pull the dash, replace the evap coil and the heater core (cheap insurance). I had to do the whole system though because the compressor was making funny noises too.

Have you seen the drain putting out water. Just a shot but if its blocked it will do what you are seeing.
Mine was blocked a couple years ago. After putting a little shot of compressed air the thing drained something like 3 quarts of water. A wire up the drain a couple times shook some junk loose and it hasn't occurred since.

Draining fine. I'm taking it back to the mechanic on the 25th and giving him instructions to fix whatever it is. I moved to the lake last week in a truck that the AC lasted for an hour at a time on a 2 1/2 hour trip. This is what I know about the AC. It starts out when it is cool outside early in the morning and puts out 45 degree air (Infrared thermometer). Running down the highway and within a half out the output temp is 60 degrees. Another half hour and it's 75 degrees.
At that point I turn it off for a half hour, start it back up and its putting out 65 degree air for about 20 minutes, then it goes back to 75 degrees.

That is annoying. I parked my GMC when the AC went out.

I can afford to let it set up until the last week I am in Houston as I am retiring at the end of the month. The plan is to drop it off at the mechanic shop and let them keep it until they've fixed it.

Do a feel test. If the low side line (Bigger Line) is cold going to the dryer and the dryer is cold, Then the problem is in the mode doors! If its not cold, then you still gotta look at the pressures. If the pressures are good and the low side is not cold, then either a liquid line (where the orifice is) or there is too much oil in the system!

Another thing to try(sometimes works), is to disconnect battery for a few minutes. When you reconnect battery, sometimes everything resets and begins working fine. Worth a try...worked for me on my AC issue.

Cummins use an electric fan clutch. The tech who looks at it needs to look at the duty cycle of the fan clutch. If it is 85 % and the high side pressure readings are above 275 you have a problem.

The fan clutch was replaced about a month ago. Shortly thereafter the orifice tube was replaced. The AC issues have been ongoing since last October. Since then the Compressor has been replaced, The Mode Doors have been checked, The orifice tube replaced and the fan clutch failed catastrophically and was replaced.
If it ain't putting out cold air after the next time they get it, I'm headed toward the Toyota Dealer for a trade in.

I'm seriously thinking there is a clog in the condenser or the evaporator core is very dirty and freezing up on you. Read my post above.....

The shop owner suggested that's the next thing they check. The compressor was replaced last October. I think it was leaking.

When this happens does the air flow drop but blower still sounds like it going full speed? If the system is freezing the air flow out the vents will reduce or stop but you'll hear the fan still operating normal. I might have missed what year your truck is but if it's a later model like 2007 and up you might consider taking it to a dealer at this point. New ac system are still the same as forever mechanically but now use sensors and computers to control the operation. Some smaller shop equipment can't monitor those ac sensor to see what's happening at time of failure. If the evaporator temperature sensor is bad it will do what yours is doing. At the dealer we can monitor ever sensor in the vehicle to determine what is going wrong. Some people think dealers are expensive but if they fix it right the first time it can save you a lot of money in the long run.

Wha every you find out that's the problem please post it so we know for the next guy. I had two shop tel me it will cost about $200. buck just to tell me what wrong with mine, it's losing coolest.

Well as a ase master tech, (ask someone else...ase) with no known knowledge or vehichle type, brand ,I may have missed it, it obviously sounds like a low freon or weak compressor, hence when eng cold, no heat in radiator,condensor, it will cool, after a little eng heat not so much, so with no gauge reading, etc, ki da hard to tell, if we are talking suv with rear air, or a ford, a reman comp WILL NOT WORK PROPERLY. ... dodges just don't cool enough from the factory.. so with a little more info, maybe some gage readings, vehichle, etc, I'm sure couples team,myself, ot triton ,can lead u in a rt direction, A/C systems are fairly easy to figure out, maybe not the real new systems, but....

2008 Dodge 2500 6.7 Cummins. Compressor replaced in October of 2015. full of Freon. It's going in the shop on Monday for the last time. If it ain't right then, it's going somewhere else, like maybe the used car lot.

If the drain is working with those symptoms I would pull the dash and clean the evaporator.
You have to pull the dash back to get to the AC system and its a pain. While you're at it you might have them look hard at the heater core.

Its in the shop this week. I told them I wanted it back Thursday....With cold AC.

Anything resolved? What it was?

Pin hole sized leak in accumulator. Lost 1/2 lb freon. Accumulator replaced under warranty from original repair.

So the AC is still freezing up. Drove down from the lake today and by the time we got to Houston, no A/C. Took it to the shop. Compressor completely froze over. Diagnosis: Thermister. They are replacing it in the morning.

If the air is really cold and u turn down the blower, it will freeze up, try adjusting the temp control as well, dodge has a issue with that, alot of cars and trucks have the issue....

New Thermister installed. We'll see if this is the fix.

Good luck man. I know you really don't need this aggravation.

So far, so good. The real test will be when we go home tomorrow.

Sounds like the low pressure switch is bad. They are cheap and easy to replace yourself. Good luck, hope its fixed.

It is no longer freezing up for sure. On the way up yesterday it appeared to be heating up a little, so I went from recirc to fresh air for a little while and it cooled back down.

Still not fixed.

The latest diagnosis is the dual zone heating/ cooling switches in the dash. Switches ordered and I should have it back on Friday.

Both my wifes yukon xl, and my 2500HD have the same issue on humid days. It's a design problem with systems using r134a. The fins on the evaporator are so close together that some moisture just does not drain off of them. that water freezes up, and as more moisture builds up and freezes it cuts down the airflow, and the temps coming out of the ducts rises. it's usually not around town driving, but when on the highway (AC is more efficient on the highway with air blowing over the condensor, and compressor running at a constant RPM). It usually takes over an hr before it starts to happen.

We just turn off the AC switch, and turn the fan on high. Usually about 7 to 10 mins later the temp rises to the outside temp and the airflow goes way up (out of the vents). We then turn on the AC switch again and enjoy the 40F temps out of the vents.

This happens every summer since the vehicles were new..... and are now 15yrs old. We even had the entire AC system changed on her yukon when the compressor starting rattling (I had the compressor (new, not rebuilt), condensor, accumulator, orifice tube, rubber hoses all changed) out a few years back and it did not change this behavior at all)

Give this a shot to see if it helps your problem should it re-occur after they change out the dual zone switches.

Turns out although my truck is an 08, the switches installed were from an 09. It appears my truck was a late 08 and they changed the switches to a different part number in 09. Mine has the 09 switches. They had to reorder. Expected in Tuesday.

It's been working just fine for the last couple of weeks, I think it's finally fixed.

Wrong. Left the 27th for MA and it carped out in Mississippi. Froze up again. Took it back to the guys that supposedly fixed it before, when we got back home. He calls today and says no evidence of the dye that was put in the frein anywhere in engine compartment. That tells me the problem is somewhere in firewall or behind the dashboard. It also tells me everyone has been claiming it was fixed without having to pull the dash. The guy filled it with Fremont at no charge, but told me today that shop was closing down for good today. Looks like next stop is a dealer.