Any Car A/C guys on here?

DannyW

Senior Member
The a/c in my 4Runner cools okay…could be better, but I have had worse. But I think there is an issue that needs to be addressed.

On a typical 90 degree day, my a/c will blow 46-47 degree air…I have measured it about 4 inches in the vent with an accurate thermometer (Thermapen). When I press the RECIRCULATION button, the air cools even further, about 2-3 degrees cooler.

Bu with the recirculation ON, the a/c will cool at 45 degrees for 5-7 seconds, and then the compressor switches off and the air warms by 5-6 degrees. It stays that way for maybe 5 seconds and then the compressor clicks back on and sends 45 degree air again for a few seconds and then switches off again.

It does this constantly…max cool for a few seconds, then off for a few seconds, and then back on again.

This constant on-off-on-off-on-off worries me. I checked my wife’s car and her a/c does not do this. And it only seems to happen on my car when using the recirculation button.

To be clear…I am not concerned about the temperature of the air from the a/c. I am more concerned about the constant switching on and off, especially on long trips where it does it for hours at a time. Intuitively, I think constant cycling could stress the compressor and cause failure.

Is this an issue that I should be concerned about? Any idea of what may be causing it and how to fix it?
 

GoldDot40

Senior Member
How old is the vehicle? How many miles? The temperature is just a few degrees of optimal for most vehicles. The short cycling could be a result of a few things.
 

DannyW

Senior Member
It's a 2005 model year with 160,000 miles. The a/c is original.

Yeah...I keep an accurate digital thermometer in a vent and I can't complain about the temp of the air. Typically, my a/c blows air that is between 40-50 degrees cooler than the outside air temperature. Over the past 2-3 months it has blown air as cool as 42 degrees, and is always less than 50 degrees except on a hot day when sitting in traffic.

But the constant cycling on-off is concerning. I do most of the repairs to my car, but I know nothing about a/c systems and how they work.
 

NE GA Pappy

Mr. Pappy
it could be the pressure switch cutting it off when the pressure drops to low on the suction side while cooling.
 

transfixer

Senior Member
Change the temp setting on your controls slightly and see if it stops doing the cycling, it could be that its just at a certain point where the temp sensors in the vehicle thinks its cold enough to stop the compressor from running ? but then it decides to let it continue ? you have two temp sensors inside the car that lets the module know how cold or hot it is much like a thermostat in the house, one is up in the dash up near the defrost vents, the other is inside the dash, usually somewhere around the center console, if your heating/air control unit is the dial type, just move the one for temp slightly to another position, if its digital just select another temp, and it could be your controller is messing up ? although I haven't heard of Toyotas having problems with those.
 

GA native

Senior Member
What Pappy said.

Most likely, you are low on refrigerant. Wally World has el cheapo gauges that work well enough to check your pressure.
 

transfixer

Senior Member
If he's getting cooling down into the 40/50degree range coming out of his vents, I doubt it is low on Freon. Hooking up gauges is the best way to tell, I don't recommend the cheapy single gauge hookups that only go to the suction side, if you have a restriction in the system and only use the low side you could have excess pressure on the high side and not know it.
You could always jump the low pressure switch and if it stays constantly on and cools then it likely is a little low on Freon, just doesn't sound like it to me since he has temps that cold.
 

GoldDot40

Senior Member
Yep, I'm leaning towards a pressure switch or compressor clutch issue.
 

kennethpruett

New Member
I know two people recently thought they were low on freon and bought can and added themselves without checking and then got no a/c. Checked and was overcharged. I think sometimes when the temperature gets higher the units work more and we noticed things more. Either way, cycling that frequent is not good and will wear your clutch out. Could be pressure switch as well as others mentioned. You'll probably need to have someone check it.
 
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