AC problems?????

[B.G. Smith]

06 3500 quad cab, compressor was replaced about 6 months ago, has been working great, usually have to cut back on fan and adjust the temp knob about 5 clicks when on the highway. All of a sudden I have limited cooling, I have to run it on recirculate to cool down inside, it will maintain the temp barely if i switch back to normal when on hwy. I pulled the glove box and can see the blend door lever/rod and actuator, it moves full stroke when I turn the heat knob full heat and back. I checked the suction pressure this AM with system set on max air and hi fan. Pressure is pretty steady at lower 20s, it never cycled off or went any lower. After it had run for a few minutes I checked the temps at the vents, mid 40s and a little higher on the far right vent. One time when I moved the temp controp slightly toward higher temp I did hear a noise like maybe the door was binding. Any ideas???? Thanks. bg

 

[PWong]

Low side at lower 20s and warmer at passenger side vent both indicated low in refrigerant, might be one can.

 

[B.G. Smith]

Thanks PWong, I will try adding a little in the morning. bg

 

[Motorhead]

Careful not to over charge. You will not cool as well if over charged too. Best to set charge with temp probe in center duct.

 

[B.G. Smith]

I added a little refrigerant, engine running at 1500 rpm, AC set on recirculate. Suction still goes to 20, receiver dryer frosted up except about 2" of bottom, compressor never curt off. Outlet air at center outlet was 33-35 deg. Put controls on normal and inlet temp goes to mid 60s. Does the compressor have a low pressure switch or clutch cycling switch? Also if it has a freeze up prevention switch it evidently doesn't work as I'm sure the evaporator was at freexing temp when the receiver drier frosted up. It seems to me that the air is bypassing the evaporator somehow or not getting a good flow through it. bg PS: I did try it again awhile ago and running 1500 rpm on recirculate the receiver/dryer did friost up a little and I did see the compressor stop but it restarted almost instantly. bg

 

[PWong]

What's the ambient temp?
If it's over 80F then the low side should be at less 30s, not 20s.
Its low in refrigerant.
There was a leak somewhere.

 

[Bob4x4]

The hi idle speed will change pressures..Check pressures at normal idle speed.

 

[B.G. Smith]

Update: Left my truck at a Dodge dealer Tuesday at noon. They called Wednesday and said they could not find anything wrong with the AC. I picked it up today and still have to run AC on high fan and max to keep comfortable in cab. bg

 

[Kirwin]

If the filter/dryer is frosting up its restricting flow or plugged. High loads will make it the expansion valve and you'll get warm air. This may not be evident in the normal idle/shop check due to compressor speed is too low to pump sufficient refrigerant to cause enough restriction in the filter/dryer to have this effect. Dealer should be able to diagnose this though.

 

[B.G. Smith]

If the filter/dryer is frosting up its restricting flow or plugged. High loads will make it the expansion valve and you'll get warm air. This may not be evident in the normal idle/shop check due to compressor speed is too low to pump sufficient refrigerant to cause enough restriction in the filter/dryer to have this effect. Dealer should be able to diagnose this though.

Before I took it in to be checked I was running it at high idle with all doors/windows closed and the and AC on recirculate and the filter dryer did frost up. I have about decided that there is a restriction, maybe in the orifice tube. Do you know if the hose the orifice is in runs all the way from condenser to evaporator in one piece?c bg

 

[Motorhead]

The orifice tube is not one piece. I am wondering if you don't have blend door issues.

 

[RWherley]

some thing to check out of curiosity, make sure your fan clutch/hub is still working the way it should. We had a similar issue with my dads 04 3500 and the fan clutch was the cause