A/C quits after 30 minutes - what causes that?

[JGorombey]

My A/C blows great for about 30-40 minutes then it goes from cold to cool. The blower still works, the air coming out is not nearly as cold. It's more of a warm-cool. If I turn the A/C off for 20 minutes or so, it will start blowing cold again. This only happens when I am driving. I tried to reproduce the problem by letting my car idle for 40 minutes with the air on, and it never did. I had the system filled and it took a half a pound. At the same time I had them evacuate and recover all the freon to get rid of moisture, etc. I also had them run some dye in the system to check for leaks.



I have had it to the shop 3 times and they can't find the problem. Of course all they do is let it idle for 40 minutes or drive it around for 10 minutes. I think the problem occurs after 40 minutes of driving.





Any ideas? Someone told me the accumulator might be full and not absorbing moisture causing it to freeze up.





Thanks!

 

[ARhine]

kinda sounds like the evap is freezing up. Look through the interior air intake in the passengers side of the air box and see if the coil is covered with leaves and other debris.



This can happen alot on oder farm tractors and we had to lift the lid and spray out the epap coil to get all the dirt and hay out of it.

 

[B.G. Smith]

As ARhine says, it sounds like the evap. may be icing up. (on the outside) Can be caused by several things, as he saiid, restricted air flow across the evap. , low refrigerant, defective clutch cycling switch and restricted orfice tube. Could also be the air blend door but that is doubtful. If the evap. is icing up, you will usually see a puddle of water from the AC drain after you shut down after coming off the highway. The clutch cycling switch is mounted in the side of the receiver/dryer. If it is working it should cycle the compressor off at around 25 lb. suction pressure and back on when the pressure gets probably above 40 lbs. bg

 

[1stgen4evr]

Iceing

My evaporator was plugged with dog hair and leaves. I have a Jack Russell that rides with me everywhere. He sheds approximately four tons of hair each month. The evaporator was indeed iceing and exhibiting the conditions mentioned.



I cut a four inch hole with a hole saw in the front face of the duct work directly in front of the evaporator and cleaned out (with vacuum, brush, and pressure air) all the leaves dust and hair. I have good ac now. Even without the dog, leaves and other debris will clog the surface of the evaportor. You can see that area through the inside intake. It is quite dark in there so you will need a flashlight. I covered the hole with black duct tape. It isn't so pretty but the cool is nice.



James

 

[JLEONARD]

He sheds approximately four tons of hair each month

:-laf :-laf

That;s funny... .

no wonder your mileage went to H...

 

[JGorombey]

Thanks everyone. I'll check the evaporator. It probably needs to be cleaned.



Does anyone know why it would work fine while idling?

 

[ARhine]

Only reason I can think of is lower pressure and not getting as cold at idle?

 

[Digger-Bear]

My evaporator was plugged with dog hair and leaves. I have a Jack Russell that rides with me everywhere. He sheds approximately four tons of hair each month. The evaporator was indeed iceing and exhibiting the conditions mentioned.



I cut a four inch hole with a hole saw in the front face of the duct work directly in front of the evaporator and cleaned out (with vacuum, brush, and pressure air) all the leaves dust and hair. I have good ac now. Even without the dog, leaves and other debris will clog the surface of the evaportor. You can see that area through the inside intake. It is quite dark in there so you will need a flashlight. I covered the hole with black duct tape. It isn't so pretty but the cool is nice.



James

Ive done this one twice, careful when you cut into your suitcase or you will end up replacing the whole deal.



Here is a link explaining the process:



http://ramchargercentral.com/index.php?action=howtoshow;id=45



BTW each time, I had a ton more junk in my box than this guy did!



Best of luck.

 

[ARhine]

theres the article I was trying to find!



I haven't got mine done yet, but I picked up a dual width outlet blank at the hardware store to cover mine up. It is a plastic one made for outlet boxes in moist environments and comes with a foam rubber gasket to put behind it. I thought it looked like a sweet way to cover the hole nicely. Just spray on some satin Fusion paint and screw it on.



Would be sealed and easily removable to clean the box once a year.

 

[1stgen4evr]

Ac

Well the four tons of dog hair is a swag but if it AIN'T four tons, it is close. Peer into the air duct and carefully plan where you cut the hole. I have done this on three of my trucks and I was a bit off to the right on the first one. There is some clearance behind the outer pannel but you don't want to go gougeing in too deep. I set the pilot drill on the hole saw as close as possible so it wouldn't run in and pierce the evaporator. As with all hole drilling, check to see/know what you are drilling into.



"Does anyone know why it would work fine while idling?"



My guess on that is, at idle, you don't make enough cool to have the thing freeze up. If you want to investigate more throughly, cut the hole and watch how it progresses. But you can take my word, it does freeze. My first indication that I noticed was that the air volume coming out of the registers was less and less. Even on high blow, there was very little air through the system.



1stgen

 

[1stgen4evr]

RCCentral

Never knew that this site existed. Great article that shows it all on the AC problem. Thanks Digger-Bear



1stgen

 

[Digger-Bear]

No problem, I learned about this site (TDR) through that (ramchargercentral.com) list. Guess what comes around...



BTW, When I cut my opening, rather than drilling and hoping for the best, I used a dremmel (sp) tool and barely broke through the surface of the plastic. I really was, and am, paranoid of cutting anything valuable!

 

[csnider]

I cut a square hole were the evaporator is and made a square aluminum plate that covers it. mounts with screws and blind nuts . . I clean out the Leaves and Rottwieler hair every summer. . still ices up sometimes but not near as much as when it was clogged with junk. . Maybe I should have my charge checked?... .

 

[B.G. Smith]

Ive done this one twice, careful when you cut into your suitcase or you will end up replacing the whole deal.



Here is a link explaining the process:



http://ramchargercentral.com/index.php?action=howtoshow;id=45



BTW each time, I had a ton more junk in my box than this guy did!



Best of luck.

I have a 89 Ramcharger that I disected the AC housing on some time ago and removed the trash, I used a tire re-grooving tool with a modified blade. (looks like an electric soldering gun) I saved the piece I cut out and just taped it back in place in the hole. I cut out about 2 1/2" X 4" hole. And yes, there is not much room between the box and the evaporator.

 

[TKingsbury]

My truck has the same problem, my truck sat under an oak tree at the previous owners house. I need to replace my heater core, so I'm gonna take it apart and do it up real nice. I used to have to do this all the time on the garbage trucks at work, they would plug up with dirt and well, uh garbage.

Travis. .

 

[JGorombey]

Thanks everyone!! I'll try it soon and let you know the outcome.