A/C System Cycling

Hi All,

New 2012 Tacoma, 4x4 SR5 Double Cab. Question in regards to the A/C System that I did not see addressed in another thread for the 2012s. My A/C system, operating in all ranges of outside temps, cycles on and off ever 15 seconds blowing cold air for approx 6 seconds then slowly starting to less cool, then repeating the cycle over and over. Truck taken back to dealer who check the system, pressures, ect and stated that the 2012s have a high efficiency AC system that is designed to operate that way. Tech also stated that he looked at another Tacoma, same style and year, and it operated the same. Tech is reliable to date.
My issue is this. Normally on every prior car I owned an AC compressor will run, when selected, continuously providing cold air when mechanically sound. I have never seen a compressor cycle on and off in a normal state (cycling is usually associated with high/low pressures).
SO...bottom line, is the system, cycling every 15 secs or so, operating in a normal state and this is new technology for AC systems, or do I have an issue with a brand new truck?
Thanks all.

 

I also have a 2012 V6 and the air conditioner cycles as well, especially if the temp dial is set back from maximum cold. The bottom line to me is it keeping you cool? In Oklahoma we have a month and a half of plus 100 degree temps. My truck has the best air conditioner of any vehicle I have ever owned! Cools the double cab off fast and keeps it that way. If its not cooling I would visit the dealer again, otherwise don't worry.

 

My 12 runs and blows cold air as long as it has a demand. No cycling that I have noticed. I'll let others weigh in but I think they are stroking you.

 

U need a little deeper understanding of AC regulation. The compressor can't just run forever; the evaporator will get very cold, which feels awesome until ICE grows all over it and blocks the airflow. If the evaporator is blocked when the compressor is running, there's a chance some unboiled refrigerant will make it to the compressor and hydrolock (aka DESTRUCTIFY) the thing. The system will periodically lower the refrigerant pressure to allow the evaporator to warm up.

There are multiple monitoring methods, but the most common are either a thermistor or temperature-calibrated switch very near to the evaporator core's output side.

For the former, the thermistor will lose resistance as it gets colder, and as a calibrated sensor the computer can tell when it's at the proper temperatures to turn the compressor off (cold enough) and back on (warm enough). I did a little trick on my Fit with its thermistor - I made a 190k ohm parallel switched circuit that would trick the computer and give me the choice of either a 45-55F range (stock) or 34-42F range (killer on summer days... passengers always said "PUSH THE BUTTON!")

With the latter, there isn't much of a computer needed. A temperature-regulated switch performs the same function as the computer-thermistor system, but there isn't much adjustability capability with that one. However it is very simple and inexpensive.

You may be referring to the multiple types of compressors there are. The Tacoma's (as well as most vehicles) use a clutched non-variable compressor. It simply shuts on and off. Some more expensive compressors are capable of lowering output pressure on the fly to facilitate the warming process, which gets rid of that annoying on-off surging ours do.

When it starts cycling that much, either the system is calibrated for a high temperature (my Fit was like that, it cycled 4-5 times a minute on low fan. It's a lot faster to cool to 45F than it is to 35F), or the refrigerant is low. It can trip the low pressure sensor once it moves enough refrigerant into the pressurized side, causing a repeating rapid cycling.

The blower fan in the truck also regulates cycling as it controls airflow across the evaporator. It will cycle a lot on speed 1, but will likely never turn off on speed 4. You can use this to rule out whether low refrigerant is your issue.

 

I have a 2012 and have not noticed my air cycling at all, I've run it in high and low fan speeds...To be fair tho i haven't really had in on the highway much..I know my Nissan would cycle and you could feel the drag on the engine when it did..I'll pay better attn when I take it for a longer cruise

 

its normal

 

This.

My previous 99 Pathfinder was like a greenhouse, I'd be lucky if after a half hour in 90 degree plus temps I'd stop sweating. I'm freezing within 5-10 minutes max in my Taco.

 

Good post iroh! I agree.

To the OP every 15 seconds sounds like excessive cycling to me. Something is wrong.

 

I like it cold so I always put on max? I have never notice this.

 

Normal for the compressor to cycle on and off.

I can't comment on the air temp coming out of the dash. I've never noticed any issues with mine.

 

I'm glad someone made a thread about this. It's subtle but noticeable if the vent is blowing right on your hand. I've noticed it on my 2010. Sounds like it's normal from the responses in here so far.

 

Normal yes, but if the OP is actually noticing a temp difference every 15 seconds, I don't think that's normal at all.

I find that mine (also a 2012) runs great...and the temp is pretty constant, definitely not fluctuating several times per minute. Granted, I'm not holding a precise thermometer up to it...but I definitely don't notice anything strange.

It's been in the 90's (and sometimes in the 100's) for about a week now here where I am with very high humidity, and the a/c has been just awesome.

I guess my questions would be:
Is your a/c keeping the car cool?
Are you actually hearing the system audibly turn on and off that frequently (15 seconds)?

If the answers are "no" to "kind of" in the first question and "yes" to the second question, then I'd say that's abnormal behavior, based on my experience.

 

It still seems to do a very good job at cooling the cab. Summer in the desert is routinely over 100 and sunny, but I have no complaints. I always sweat my balls off in my wife's Civic even with the a/c on full blast.

 

Normal. Every time it cycles off the air temp will rise. Then the comoressor cycles back on and the air temp drops. The extent of how much the temp rises and falls depends on things such as outside temp and humidity. But it must cycle off to keep the system from freezing, just like Iroh stated in his post above

 

Catching up with the posted questions...

Yes, the system does keep me cool (with the slight variation in temp that is noticible close to the vent, thanks on that TACK).

I do feel the compressor/system engaging/disengaging (its slight, not major) during the cycle times discussed, but no sound is associated with it.

Bottom line based on all inputs I am confident that the system is running as advertised, but will keep an eye on the system pressures to make sure. This was just very different than I have had in previous vehicles and did not feel right, especially for a new truck.

Thanks all for the replies. Really appreciate the insight from the group, especially the breakdown of the system from Iroh. Nicely done.

 

Who's TACK?

 

Just some dude.

 

a dude dressed as a dude disguised as another dude

 

So I was ready to post that after taking my 2012 on the highway that my condenser doesn't cycle every 15 seconds, more like every couple of minutes. This morning while sitting at the cash station with the window open and the air on, sure as shit every 15 seconds the condenser cycled. My fan was on the second lowest speed and it was already 85 degrees and humid as hell. As someone mentioned earlier, sounds like a thermistor opening and closing dependent on temperature, and cycling the condenser on and off. Looks like this is by design and there is nothing wrong with your Tacoma. I have also found things different with this truck than others I have owned (this is my first Taco) and it is nice to read that these are not problems at all but only design differences. Great wealth of info available on this site that's for sure but friggin addictive. Ha
Cheers

 

I'm reviving this post as my new 2014 4x4 TRD does the same thing, (cycling every 15 seconds). After 3 trips to the dealer, one recharge, a connector cleaned on the compressor, and then them keeping the truck for 3 days they come back and tell me it's normal. WTF !! They spend all this time and money on something that's normal? Bullshit.
Lots of people say they do this to prevent freezing of the evaporator, I thought R134 wasn't as efficient as R12, my 1987 Grand National (R12) will give you frostbite and it never cycles the compressor and never freezes the evaporator.
Are there any other 2014 owners that have the same issue? My compressor is on for 15 seconds them off for 5. this repeats no matter the fan speed or OAT. It is very annoying.