AC is cold, then heats slightly then cools back down

Hello everyone. This is my first time using this forum so I hope i make sense. I have a 2003 4runner and am having an issue the AC. When I turn on the AC it blows cold but will warm slightly and then cool back down. It will do this off and on the entire time I drive it. I replaced the air blower motor a few mo the ago and it is working ok though the air flow doesn’t seem as strong as it was before I replaced it. I have looked at the air mix actuators for both the drivers and passengers side and both are working. I have looked at the air filter and it is clean but I don’t know what to do next. If anyone has any ideas I would love some guidance. U less of course this is just something that happens as the 4runner ages. Oh and the mileage is at 168,000. Thank you in advance for the help.

 

On a vehicle of that vintage, you may have enough refrigerant for the compressor to run, but not enough to cool properly. You will probably need to replace the receiver dryer as you probably have not replaced that in a long time either. The receiver dryer acts like a filter and catches any moisture that may have gotten in the system.

To accomplish a thorough check, have an air conditioner technician evacuate the refrigerant in your system using a scale. After the refrigerant has finished evacuating, compare the weight on the scale with the recommended amount (weight) of refrigerant on the placard under the hood. I would be surprised if after all this time and mileage that it has the proper amount based on the way you describe the current operation of the air conditioner. Since the refrigerant is evacuated, this would be a good time to replace the receiver dryer. after that is accomplished the technician will evacuate the system again (vacuum), and the results of that will partially tell the tale if there are any leaks in the system. Consider that your condenser in front of your radiator takes a lot of abuse from road debris, bugs and stones impacting at freeway speeds. If the system passes the vacuum test, then refrigerant can be introduced until the charge has been completed by weight. A good technician will check for leaks during and after the service, because what might not leak under vacuum could very well leak under operating pressure. The system normally operates under pressure, so it should be leak checked with a sniffer and/or a black light as most compressors have ultraviolet dye in the oil that lubricates the compressor. Lastly, a good techician will have gauges hooked up to the compressor during servicing to look at the readings on the pressure and suction side. If there is not the required range difference between pressure and suction then the whole system will not operate properly. Lastly, the expansion valve operation would likely be exposed by the gauge readings if it was not operating properly.

Hope this helps.

 

Ok thanks for the guidance