Auto Repair Help
Carl’s Corner – Auto Repair Help


By Carl O’Reilly

The air conditioning system is not cooling as expected. The air conditioning system may require an extended period of operation to reach the desired output.

Low refrigerant level is the most likely cause of poor cooling from the air conditioning. If there is no cool air coming from the air conditioning system, an electrical malfunction could be the cause. A defective relay, compressor clutch coil or damaged compressor are all possibilities.

The air conditioning system is equipped with safety switches that automatically turn the compressor off when the A/C refrigerant level becomes low. This prevents compressor damage, since the lubricant for the compressor is circulated through the system by the refrigerant. When the pressure switches are activated, power to the compressor is interrupted regardless of the position of the A/C dash switch. Recent regulations have prevented most consumers from doing the repairs. Special equipment is now used to remove the refrigerant, referred to as “evacuate” prior to opening the refrigerant system. Special leak detectors are used to detect leaks around hoses, fittings, and valves. Once pinpointed, the leak will have to be repaired once the existing refrigerant, if any, is removed.

The refrigerant system is under high pressure at all times. During operation, the high pressure side of the refrigerant system can reach pressures of over 275 PSI. Use extreme caution when working around the A/C system. Never disconnect or vent the refrigerant to the atmosphere. Refrigerant can cause extreme frost bite or blindness if it comes in contact with your skin or eyes. Repairs to the A/C system are best left to trained service personnel using the proper test and service equipment. Repairs can be made by the consumer, however, the system should be evacuated using the proper equipment by trained service personnel prior to any component replacement. After the system is repaired, it will have to be recharged using the same type of equipment.

52 responses to “Diagnose Ac System Doesnt Blow Cold Air”

  1. Brian says:

    I recently tried recharging my a/c system (5.3L chevy Silverado truck) with an “easy charge” system from my local auto parts store (attaches to the low side and press the trigger). I think I overcharged it because now the compressor clicks on for a couple seconds then off and only warm air is blowing. I bought a set of guages and an evac pump and evacuated the system, put in a new expansion valve, and tried it again, same result. The reading on the guages are LOW SIDE=high & HIGH SIDE=low. Did I f-up & need to replace the compressor/accumulator?

    • carl moyer says:

      sure would like to know the answer to Brian’s problem as I have the same exact headache!

    • Nick says:

      Your compressor brings down the suction pressure and increase head pressure which is your high. Something is wrong with your compressor bro

    • Brent says:

      If you unplug the connector to the cannister on passenger side that is wrapped in insulation, stick a paper down to complete the circuit, it will keep the clutch engaged so the suction side, low side will take the refrigerant in, with the clutch clicking off and on it won’t except the coolant, only that second or 2 it’s engaged.

  2. Mr Sames says:

    Due to the expansion in the air compressor there are very advanced compressor are available in the market with the low risk factor and high power facility.

  3. peter says:

    I evacuated the system and disconnected the lines to check that the condenser isn’t plugged by blowing by filtered air through the system.

    The low and high side switch works. If it has too high of a charge, the compressor won’t turn on. If it has too low of a charge, the compressor won’t turn on.

    I replaced the drive belt and adjusted the tension during installation.

    The central console switch(s)work.

    I’m not sure if the receiver / dryer on the R/F fender well is bad or the evaporator under the dash is bad.

  4. Brandon says:

    I have a 2005 Chevy Avalanche. It is a 1500. My AC has always been a little weird. At times it would blow hot air, but would stop after the car was turned off and on. However, now it only blows ambient air. It was over charged a bit at one point, but no longer. I checked the electrical box for the AC fuses. I found out that the AC Compressor 10 A fuse will immediately pop when I turn on the AC, but air still blows out the vents.

    • Jesse says:

      Had this happen on a 2005 Impala. Kept popping the AC fuse. Did some research and found that there is a diode on the compressor plug back about 3″ from the plug. Normally, it kept the large amount of energy from the clutch coil from back feeding into the circuit when it shuts off, when it’s good. When it fails, it creates a direct short across the clutch coil wires, BAM!, blows fuses every time. Cheap part, $.50 at Radio Shack, if you still have one around. You have to peel back the tape from the clutch coil plug to find it. It has to be soldered in. Fixed it and AC worked great after that.

  5. jim says:

    I have a 2008 town and country. My ac is blowing warm air. There are no leaks that I can see, I also used the dye and UV light. The compressor engages when ac is turned on. What can be the problem ?

    • HT Alexander says:

      We have the sane vehicle and same issue, I added R134a last night and when I turned on the AC last night it was cold air but this morning it was warm air again,not sure what to do now

  6. Brittney says:

    Ive replaced the conpressor and condensor and still blows very very hot. Any ideas as of why.


  8. henry says:

    hi i have a 1991 chevy s10 i had a certified ac technicion install all new parts in my truck i even changed the radiator thermostat water pump fan clutch i even installed two electric fans nfront of the condensor and it keeps blowing my compressers within hrs and will not blow cold air thru my vents i dont know wat else to do evben the tech cant figure out wats going oni need help

  9. george savoy says:

    Hi , My name is George I have 2003 S10 pick up Air Condition is working , I just change new Blend Door Actuator part and still blower hot air but I check Air Compressor and Condenser is working well and cold but inside truck Dash board blower hot air while AC is on ! I Cant find what is Troubleshooting ! So can u feedback me Help Please !Thanks George

    • Jay says:

      Try The Cabin filter Under The Dashboard

    • Forrest says:

      The condenser is cold? The coil in front of the radiator at the grill? That should be hot to the touch.
      I have the same problem, from my short experience in residential HVAC my best guess is that the compressor is pumping reversed. Or the A/C is turning on the Defrost maybe? I can’t find anything about a cold to the touch condenser coil with A/C on. the only reason I noticed this was because I haven’t put my grill back on after other recent repairs.

  10. Joe says:

    I have a 5.3 1999 GMC 1500 Pick up
    The AC blow cold for about10 minutes then blow hot. shut truck off for a while then blow cold for 10 minutes then hot. Had it recharge no change. Was told it might be the clutch kicking out when it gets hot.

  11. albert says:

    the air blows but it doesn’t throw cold air and I can’t hear the a/c turn on, on the engine e

  12. Ganiyat Ismail-Balogun says:

    My car a/c will work for a minute then stop for 5minutes then pick up again .my car is sienna 2001 .pls what can I do

  13. Robert Willbee says:

    I have a 2001 chevrolet silverado,only blowes ambient air
    on the recycle side but vary cold air on the maximun a/c side when the a/c is on the recirculating side the accumlater has no build up of moister on it, could this be low pressure, cause it is not cooling
    any help would be greatly appreciated

  14. dantil says:

    The air show sign outside that it’s getting cold but it’s want get cold on the inside……I have a 02 freightliner Columbia

  15. Bob says:

    2005 dodge pickup ac works when idling when under power the clutch kicks out
    Then kicks back on after 10 to 60 seconds more so pulling a trailer

  16. Michael says:

    Hey guys & gals i have a 2003 gmc envoy XL with AC issues…. I’ve replaced the upper and lower pressure sensors/things and had the ac checked and recharged last summer and it seemed to work fine as long as it was in the driveway not moving…. As soon as we would get out moving it would Quit blowing cold air. The compressor clutch is NOT SEIZED!!!! Like i said before, i had everything checked last summer and it was all good with new sensors and ac recharge and no leaks….Hmmmmm I’m Very Confused. Please help me anyone that might have an idea or suggestion to something that i may have over looked….. You can also reply to my email
    Thanks SO SO much for any suggestions!!!

  17. cindy says:

    in my 2008 forenza suzuki, an AC compressor kit was installed. everything works, but only cool air is coming out, not cold..they checked everything about the compressor and still cant figure out why…what else could cause this problem, maybe “control valve” stuff?? please help

  18. cindy says:

    in my 2008 suzuki forenza, a new AC compressor kit was replaced, after 3 trips back to the shop, ONLY cool air comes out, not cold….any suggestions as to what else could be the problem, maybe a “control valve”?….help

  19. Brent says:

    My A/C is properly filled with refrigerant, but not getting cold air, just cool and won’t keep the cabin comfortable in this Texas heat, is it the 134a or should I have a shop put the good stuff back in, never had a problem with the 134a before till recently

  20. Don says:

    I have a 2003 GMC Sonoma compressor is working clutch is working new pressure sensor new blend door actuator
    but still no cold air what do I check next?

    • Al Smith says:

      The most common cause of compressor cycling and no cold air being produced in my experience has been an over-serviced system. An over serviced system does not have sufficient pressure differential between the high and low sides of the system. It is this pressure differential that allows the compressed gas in the high side to expand rapidly after it passes through a restricted orifice and enters the evaporator on the low side (Rapid gas expansion causes dramatic temperature drop) . The over serviced system reaches the high pressure cutout set point which cuts out the compressor after the compressor has operated for only a few seconds. The short run cycle of the compressor never allows for a pressure differential to develop and results in very little flow of refrigerant through the system. AC systems must be serviced precisely to manufacturers specifications as different systems may have different high as well as low pressure cutout set points. Try lowering the system pressure to remedy this problem (This is usually counterintuitive).

      A similar problem is when compressor cycling occurs after the system has been operating normally for the first several minutes of operation. After a period of normal operation, suddenly the air goes warm and the compressor starts cutting out after a very short run cycle. In this case, the system may be contaminated with humid air. The dryer may be maxed out and the humidity is freezing up the orifice where the refrigerant passes into the evaporator, effectively clogging the system. This clog creates a rapid rise in pressure on the high side causing the compressor to cut out. With no refrigerant passing through the orifice, the area starts to warm and the “Ice clog” thaws allowing refrigerant to flow again only to refreeze after enough ice has collected in the orifice again. This problem can result in erratic AC operations where it seems to operate fine one day and not the next. Ambient air temperature and air flow around the evaporator orifice and engine temperature may be conditions that affect whether the orifice freezes up or not. To remedy this issue, have the system serviced properly by installing a new dryer and evacuating, drying and servicing the system per the manufacturers specifications.

      • Greg C Harper says:

        Thank you so much!!!! Just had my condenser replaced, picked up the truck, drove home and no AC. Tried draining a bit of pressure until I saw the compressor running steady and finally have cold air!!!

  21. Justin F says:

    I have a 2004 Chevy Impala 3.8. I have checked all of the fuses and relays as well as turned to center bolt on the compressor. The fuses and relays are good and the compressor turned freely. I have also checked the pressure in the system. It reads full. Is it possible the compressor is bad. Or is there anything else i can check?

  22. Jman says:

    a/c just blows hot air but no pressuer on low side

  23. Edward says:

    I have a ’02 silverado ac is fully charged blows hard but not cold.

  24. Rob says:

    2010 GMC Sierra; A/C is blowing warm air, compressor kicks in and out consistently while on and running. Tried A/C Pro but when hooked up the pressure guage goes all the way up into the Red when compressor shuts off and then down to safe levels when engaged.

  25. Rickie says:

    2002 chevy truck ac stoped cooling . Compressor want engage even using a paper clip to jump over the pressure switch connector . Started doing this off and on for about a week but now want cool at all

  26. Tony Zink says:

    I have a 2003 gmc sierra the clutch isn’t pulling in . I have 12 volts dc at the connector at the compressor is there any thing else I could be missing or should check before I replace the compressor ?

  27. Howard says:

    I have a Chevy truck several years old. It was blue when I bought it new. My truck started blowing “not cold” air after I changed a faulty blower resistor (which fixed my fan speed issues). Now my step-son-in-law’s ex-mother-in-law has moved in. She has a brand new Jeep that likely blows cold air but all she can talk about is Arizona, which is waaay hotter than here in the south. My truck a/c is still blowing “not cold”. I think recharging it would be a waste of time until I know more about what’s causing the hot air problem. Any ideas?

  28. Tony says:

    I have a 03 chevy suburban just replaced ac compressor and dryer and have no air leaks out in a hour added dye to the system and no visual leak detected anywhere under the hood but it all leak out the vehicle has rear unit that blows hot too could I have a leak in the rear what’s my next step please help in puzzled with this one

  29. Cesar says:

    Makes Ticking Sound When Turning On A.c.

  30. I have a 2002 conversion van. GMC 2500 with front and rear air. The compressor is cycling, the refrigerant si at the proper level but the air is just slightly cool. Is there some kind of electrical problem like a valve?

  31. Bob sizemore says:

    I have a 1995 GMC Sierra 1500 the a/c works, but not on high. If you turn it on high it just
    doesn’t blow. Any suggestions would be appreciated! Thanksbob

  32. Jennifer says:

    I have a 2005 Chevy Colorado ac blows hard just not cold mechanic said it’s not compressor it is something electrical what could this be?

  33. Terry says:

    I have just reolaced the accumulator in a 98 Ford Ranger the accumulator frosts up like its workinf but it wont blow into cabin.

  34. My AC does not have low pressure then what

  35. barry says:

    I have a 2011 chevy colorado. The A/C works great for about 1 hour, then it start to warm up.. is like it is low on freon. The compresser kick in for 20-30 sec, than kick out for 10-20 sec. When I bought the truck, it have a Refrigerant Temperature from a refigerator. (before i did any thing to the truck, the A/C was working great, just not correct) I replace it with the correct part. GM 89018791Sensor Asm,A/C Refrigerant Temperature and a new wiring harness. GM 89019303Harness Asm,A/C Module Wiring.

Leave a Reply

Your email address will not be published. Required fields are marked *