A/C System Cycling

99.999% of the people here, when they see the terms "AC not cooling as well as expected" and "thermostat" will make the natural association "this is what regulates the cabin air temp..." The thermistor does NOT have anything to do with the cabin air temp. The Tx valve prevents the system from freezing, the thermistor seems to be an energy saving device that disables the compressor at probably the same point (or close to it) where the Tx valve shuts off the refrigerant flow into the evap core.

As far as the good old days, things were not that different. I had a '72 Dodge Challenger that used a classic Tx valve to control R12 flow, just as we see today to control R134a flow. That Dodge compressor cycled solely based on the high pressure limit switch (and the low pressure if it fell too low).

I don't remember seeing any actual thermostats back then unless perhaps in a Lincoln or something. Everything I worked on back then used a water valve to control hot water flow into the heater core, if the cabin was too cold the water valve was opened and it undid what the evap core did, namely add heat back in. That went away because the water valve itself had many problems, and could cause catastrophic water loss and disable the vehicle. Along came the blend-air approach where if the actuator fails, no radiator fluid is lost.

 

I have a 2012 Tac. I am also having problems getting the cab to cool down on really hot days. When the a/c is first turned on, it seems to blow pretty cool air. But once the compressor starts cycling more frequently, the air from the vents seems warm up some (not really warm, but not cold enough). I have done the self check (diy A/C bottles) and the R134 seems to be in working range.

 

I am curious if it makes a difference when you change the temperature setting on the heater knob while the AC is running. As if you wanted AC but not super cold so you turn the temperature knob to the middle (1/2 red 1/2 blue) setting. If your AC system is "high efficiency" it might be designed to achieve moderate heating by cycling the compressor on/off instead of running all the time. Just a thought.

 

You are checking it wrong. Those bottles only give you a partial story. You can do more damage than good that way. Take it to someone that knows what they are doing and you may find an entirely different story.

 

I will probably take it somewhere for a look. It is definitely not working as it should be.

 

Cycling of compressor is normal , but every 15 seconds sounds abnormal. Did anyone thing that maybe the fan is not blowing enough air through the condenser? If the condenser does not have proper air flow the high side of the A/C system will rise quickly and shuts off the compressor clutch. I believe on these Tacoma systems the radiator fan has a gravity clutch that could fail and not spin fast enough to provide proper air flow through the condenser.

 

It is a silicon oil controlled clutch. And yes that "could" be an issue.

 

oh , okay that's good to know for next time I need to troubleshoot my Truck. I'm no mechanic but am familiar with auto A/c systems I completely replaced the A/C system in my VW new beetle, talk about a nightmare.. LOL

 

Can you share more information about how you added the "AC overdrive switch"? Wiring diagram/pictures?

 

The problem I’m having is mine kicks on for like 3-5 seconds then kicks off for 10 seconds. Not sure what to do honestly.

 

It sounds like it’s low on refrigerant, it has a safety switch that saves the compressor. If it’s low it means there’s a leak.

 

Well guess I’ll buy a can of refrigerant with the dye...

 

Yep

 

Literally just put in a full can of refrigerant, said when the compressor kicked on that it was good. So that’s making me think it’s the high side that has a leak

 

I would put in the dye with my main goal to find the leak and repair. Then I would add the r134a by weight according to the sticker under your hood. And that’s after it was vacuumed.

 

I’ll definitely be looking into that for sure