A/C compressor cycling conditions?

So I just replaced my Evap core, all o-rings, and upper hose w/ orifice tube; due to a leak.

Evap deff had leak and after vacuum I let it sit two hours; gauges didn't budge at all. I would assume at this point, no leak.

I charged it six or so days ago; at idle, one 12Oz can and another half 12Oz can that I still had connected to the hoses. The compressor never cycled; just stayed on and temp was super cold (and still is).

I observed the elec fan kicking on for a couple of seconds and seen the pressure drop fairly quickly. It would slowly build back up and fan would kick on again. Never noticed the compressor kicking off, again, just stayed on and temp was great. Is this normal operation?

Today, on my way to work, I could hear my compressor cycling while sitting at a light. Selection was recirc and fan low; temp was still very cold. Is this normal, do I have another leak, or was my charge too low to begin with?

Cycling of the A/C is indicative of not enough R134 in the system. The cycling is a built in safety mechanism I believe to keep the compressor from burning itself up.

So then why did it not cycle when I first charged it?
I can't imagine a new leak sprung up as soon as everything was replaced.

thanasi85 said:

Cycling of the A/C is indicative of not enough R134 in the system. The cycling is a built in safety mechanism I believe to keep the compressor from burning itself up.

Click to expand...

That is totally false. It is normal for a R134 system to cycle under certain conditions. When it is 105+ here, mine stays on all the time. 104 and below, my system will cycle. Mine is charged with the proper amount of R134 (charged by weight as should always be done).

That being said, it is possible that you have a leak. Put a vacuum on it and seal it and let it sit for a few hours and see if it maintains the vacuum.

I've noticed that my AC system in my '00 is VERY sensitive to the amount of Freon in it. I have to have EXACTLY 20oz in it to provide optimal performance. Perhaps you have a touchy one like mine...

My Ranger I still run R12, and it's just like "whatever, dude, you want cold? Done."

SouthSeaPirate said:

So I just replaced my Evap core, all o-rings, and upper hose w/ orifice tube; due to a leak.

Evap deff had leak and after vacuum I let it sit two hours; gauges didn't budge at all. I would assume at this point, no leak.

I charged it six or so days ago; at idle, one 12Oz can and another half 12Oz can that I still had connected to the hoses. The compressor never cycled; just stayed on and temp was super cold (and still is).

I observed the elec fan kicking on for a couple of seconds and seen the pressure drop fairly quickly. It would slowly build back up and fan would kick on again. Never noticed the compressor kicking off, again, just stayed on and temp was great. Is this normal operation?

Today, on my way to work, I could hear my compressor cycling while sitting at a light. Selection was recirc and fan low; temp was still very cold. Is this normal, do I have another leak, or was my charge too low to begin with?

Click to expand...

The part of the quote that I bolded is the exact condition that will cause the compressor to cycle. It prevents the evap from freezing up.

Completely normal.

No my info isn't false because I had a leak in my A/C system and I only realized it because my A/C compressor kept cycling off and on a lot and it was really annoying. I then found the leak and fixed it then recharged my system and the cycling stopped after that.

Ya its normal for the system to cycle ever so often but its not normal to be siting at a stop and having it cycling on and off repeatedly as south seal is describing

The A/C pressure switch is detecting inadequate pressure. When the pressure on the low side drops to low the pressure switch tells the computer to disengage the compressor clutch so it doesn't burn up. Once it cycles off the low side pressure comes back up, the compressor kicks on, the low side pressure drops again, the compressor kicks off.....and the cycle just repeats.

thanasi85 said:

No my info isn't false because I had a leak in my A/C system and I only realized it because my A/C compressor kept cycling off and on a lot and it was really annoying. I then found the leak and fixed it then recharged my system and the cycling stopped after that.

Click to expand...

yes, compressor clutch cycling is definitely a symptom of low freon.

thanasi85 said:

Ya its normal for the system to cycle ever so often but its not normal to be siting at a stop and having it cycling on and off repeatedly as south seal is describing

Click to expand...

under the conditions he describes, it is perfectly normal.

thanasi85 said:

The A/C pressure switch is detecting inadequate pressure. When the pressure on the low side drops to low the pressure switch tells the computer to disengage the compressor clutch so it doesn't burn up. Once it cycles off the low side pressure comes back up, the compressor kicks on, the low side pressure drops again, the compressor kicks off.....and the cycle just repeats.

Click to expand...

Low pressure also occurs during low evap temperature conditions with a fully charged system. The compressor turns off until the system cam warm up and raise pressures to turn the compressor back on.
If the temp gets too low, it will cause ice buildup on the evaporator and then you have poor airflow. It can also cause poor compressor lubrication and cavitation problems.

So, while clutch cycling can indicate low freon, it's not the only cause nor is it indicative of a problem being present.

Digger87xj said:

yes, compressor clutch cycling is definitely a symptom of low freon.

under the conditions he describes, it is perfectly normal.

Low pressure also occurs during low evap temperature conditions with a fully charged system. The compressor turns off until the system cam warm up and raise pressures to turn the compressor back on.
If the temp gets too low, it will cause ice buildup on the evaporator and then you have poor airflow. It can also cause poor compressor lubrication and cavitation problems.

So, while clutch cycling can indicate low freon, it's not the only cause nor is it indicative of a problem being present.

Click to expand...

^^What he said^^

CarbonXJ said:

I've noticed that my AC system in my '00 is VERY sensitive to the amount of Freon in it. I have to have EXACTLY 20oz in it to provide optimal performance. Perhaps you have a touchy one like mine...

My Ranger I still run R12, and it's just like "whatever, dude, you want cold? Done."

Click to expand...

Well, I did do a can and another used one. If it was half, that means Id be at 18Oz. I was kind of thinking it was too low because how quick the fan would turn off and how long it would take to build pressure back up before it would turn on again. Thoughts?

Digger87xj said:

The part of the quote that I bolded is the exact condition that will cause the compressor to cycle. It prevents the evap from freezing up.

Completely normal.

Click to expand...

Maybe combination of above? It is still very cold. Ive been putting the fan on 1 and 2 on my way home after it's been sitting in the sun for 8 hours, at 90+ degrees, no tint, and a sunroof. And I love it cold.


Thanks for the input everyone!

if its cold and keeping up with demand, call it done and forget it.

Cycling is normal in some situations, like when its mild outside and you are running the blower at low speed, resulting in a small amount of heat transfer at the evaporator.