A/C Slow to Cool

[postoak]

I have a 2008 Tahoe, 5 1/2 years old, with 107,000 miles. This summer it doesn't seem to put out really cold air right away as I remember it doing in years past. Eventually (3-5 minutes) the air gets as cold as it should. The system is as it came from the factory except I had to have one hose replaced a couple of years ago. I took it in to a shop and they said the system was .6 pounds low, but not leaking. After they put the freon in, there was no change. Any ideas?

 

[Tex99Tahoe]

Seen this before, when the expansion valve/screen starts getting clogged. Funnel shaped filter screen, A/C shop has to do this...

 

[postoak]

Approximately how much to replace the expansion valve?

 

[Tex99Tahoe]

Oh ho, haven't a clue. I rarely let shops touch my stuff. Someone told me long ago that $100 would be just to hook-up the guages and recover the freon, then it goes up from there.

The expansion valve/filter should be within a few inches of the inlet to the expansion core, easily accessed...

 

[postoak]

Still don't know what is wrong, but will wait until next summer. But one thing I learned is that instead of an expansion valve, the Tahoe has an orifice, which is located under the radiator somewhere. It's a $10 part.

 

[rockenthebowtie]

Postoak your right about the orifice tube taking the place of an expansion vavle but its not under the radiator its right up on the top of the engine compartment on the passenger side next to the coolant surge tank ther is a pipe coming out of the receiver dryer that lead to 2 pipes connected together by threaded pipe nuts you put a 7/8 wrench on 1 and a 3/4 wrench on the other to break them loose and seperate the pipes now the pipe with the smaller pipe nut is the one that holds the orifice tube you kinda have to bend the pipe up to stick a thin walled needle nose pliers to pull it out... only you do need to evacuate the AC system before you open it.. the other concern I have is you mentioned in your first post that the shop you took to they had told you that you were 6lbs low... that worries me because your system capacity specifications is max 3lbs so if they put more then that like 6 lbs or more that will affect the perfornce of your AC system and or even damage it

 

[postoak]

Hey, thanks for that information on the location of the orifice tube. I am not going to work on the system myself, just trying to get ahead of the mechanics. What I said was the mechanic added 0.6 pounds (six-tenths of one pound) of Freon.

I am thinking at the start of next summer of just requesting the receiver/dryer and the orifice tube be replaced. Do you think this sort of trouble-shooting might fix the system?

 

[rockenthebowtie]

LOL... Im in denial still about needing glasses ok didn't see the .6 lol... There are many variables when it comes to AC system diagnosis however I do recommend that they may want to hook a scan tool to see if there are any DTCs in the HVAC control module..This can only be done on auto HVAC sytems..There are sun load sensors, outside and inside temperature sensors, and actuators that the HVAC contro modulel uses to maximize HVAC performance...again this is also pending on your HVAC sytem is it duel auto climate control or manuel non climate control. the other thing is the reading of the high and low pressure sides of the AC system when connected to the shops AC gauges.. nomal readings would be for high side between 100-200 psi and the low side about 40-60 psl..theres also a TSB for the concern your having on auto HVAC systems that the HVAC control module may need a reprogram TSB# 08-01-38-006.. BTW. I made a mistake the tube that holds the orifice tube is comming off the evaporator core off the engine compartment fire wall not the receiver dryer but everthing else is correct its there on the top passengers side of engine compartment... hope this helps

 

[postoak]

Thanks some more. It is a manual system, but has dual temperature controls.

 

[samotahoe]

ya our shop everytime we do any kind of service especially while replacing compressors we recommend those receiver/dryers, orfice tubes and also the condensors. most warranty with compressors require those to be replaced or they wont warranty it.