Compressor Rapidly Cycling On and Off in Car Air Conditioner

This week I’ve done some work on my 2001 Honda Civic EX.

Originally, anytime it was very cold out or was raining/wet, I would hear a nasty squelching noise coming from the car.  Then, I attempted to turn on the air conditioner on in the car last week and again – very bad squelching noise coming from the car when the AC was on.

So I took it down to a guy I know that works on cars for a very affordable price.  I took the car to him a few years back to have him replace the timing belt and serpentine belt.

Turns out there is a second belt – an accessory belt – that controls the A/C compressor.  He got that replaced and also replaced the serpentine belt while he was at it.  Problem fixed – no more squeek!  But, he did tell me that my AC was cycling on and off and it needed to be charged.

So, down to the local automotive store.  I bought one of those low-pressure gauages for about $15 and a can of R-134a refrigerant with stop-leak in it.  I know folks online say not to use this – so I won’t be using that going forward.

Got home and began to slowly put the R-134a into the car air conditioner system with the AC turned on and the temperature set fully to cold and the blower fully on.  The compressor was fully on and the car just was barely cooling before I began adding the freon into the car – but it certainly was not keeping up and was not cool enough.

As I was adding the freon into the A/C system, I heard a popping-like noise and noticed that the compressor kicked off.  Then, it happened again, and again!  The air conditioner compressor was rapidly cycling on and off.

I turned the A/C off and stopped putting R-134a into it becuase the compressor cycling was almost causing the car to die from the load it was putting on the engine.

Onto Google I went.  Everywhere I turned, people said that if the compressor was cycling on and off quickly, that meant the compressor was low on freon.

OK – so explain this to me – why was the compressor not cycling at all before I put the refrigerant into the car – and only started happening when I got about 3/4 a 12-ounce can into the car?  I was afraid I overfilled it – because the car was originally trying to cool before putting any R-134a into it.  All the forums and posts I saw indicated that people that had this problem had no cooling coming out of the car.

Called up my mechanic and he basically told me the same thing – he said that if the compressor was rapidly turning on and off, it was because it was undercharged.  But, I explained to him how it was working fine – and somewhat cooling – before putting any refrigerant in – then it started kicking on and off after adding 3/4 a can in.  I said – “Is it because I overfilled it?”  He agreed and thought that I may have overfilled it – but said he hasn’t ever noticed a car doing that before.

The Honda Civics can hold up to 22 ounces of R-134a in them.  A 12-ounce can would be just more than half of it’s capacity.

Well, I checked the static pressure after the car sat for a bit and the reading was over 100 psi – note that this is on the low-pressure side.  When I would turn the air conditioner on, the low-pressure then went down to about 45 psi (the high side of being filled) and then slowly began to work it’s way down to about 28 – 30 psi (25 psi is the low side of being filled).  Then the compressor would pop and kick off again.  Then it would pop and kick on again.  Over and over maybe five seconds apart.

I then called a co-worker that had a full set of hoses that can be used to check both high and low pressure.  At this point, I was pretty sure that it was overfilled and I wanted to see if the car was being kicked off because of high pressure – not low pressure.

So we hooked the hoses up and the high pressure climbed very rapidly when turing the A/C on.  it hit 350 – then 375 – then 400 – then just shortly after, the compressor popped and shut off.  Then high pressure then started going down – then the compressor kicked on again.  So, the compressor was rapidly turning on and off still.  As expected – the high pressure was too high.

Some of the freon was taken out of the vehicle and the guy said there most likely was some air in the line that wasn’t helping things.  After taking some out, the compressor stopped kicking on and off – and the high pressure then stayed fairly stable between 325 and 350 psi.

Test drive time!

Didn’t even make it very far and the compressor started kicking on and off again!  So, back to the hoses.  This time, I revved the car up to about 1,500 to 2,000 RPM (since the Civic seems to idle at around 500 rpm).  Sure enough, he said that the low pressure was being sucked down to about 20 PSI and the high-pressure was kicking way up again past 400 PSI.

So more was taken out until the high pressure would only be about 325 PSI at 1,500 RPM.

Alright – test drive again!  It worked!  That was the problem – it was simply over-filled.  The car no longer cycled the compressor rapidly after taking some R-134a out of the system and it cools very well.

So, the car only needed a bit more than 1/2 a container of 12-ounce freon and it was working like a champ!  With recirculating the air and the outside temperature around 80 degrees, the car was putting out about 44 degree air from the A/C vents.

So next time that your air conditioner compressor rapidly turns on and off in your car, it may not be due to low freon levels – but because it is over-charged!  Those cheap low-pressure testers that come with the charge kits only tell you part of the story.  When I was charging mine, I was well within the acceptable range – but the high pressure (which is what I couldn’t see) was telling an absolute different story!

19 thoughts on “Compressor Rapidly Cycling On and Off in Car Air Conditioner

  1. Thank you for posting this info!!! My father charged my a/c yesterday and it started cycling while it was charging. We weren’t sure what it was and went on about the day. The cycling continued so he started looking into possible causes. After I replaced a filter that was long overdue, my worry continued to grow. I came in and searched causes for the air compressor’s rapid cycling. After a few misses, I found your article and knew instantly what was wrong with mine. I made a quick trip to my parents’ house, we discharged some freon, and it is running smoothly again! Thank you again for sharing!

  2. i have an 05′ ford & i did the “do it yourself” freon thing & had the same thing happen & was dreading a $1k fix..thanks so much for posting..

  3. Had a new trane unit installed in my house. Ran find for couple of months til temp got to above hundred here in Texas. Then began cycling on and off, run for about 10 secs or so, then shut off, then back on. It appears that it too was overcharged as the a/c boys are here today. They said with the new freon they use now, repair folks are prone to overcharge the units. We will see, as this is just the first day and the a/c boys are still here.

  4. Thank you for this post!!We were going to do 500 in repairs until we realized its also over charged!!! Thanks!

  5. Thanks for the post! I was afraid I was going to have to replace the compressor in my daughters car… Came across your post & bled off some pressure on the high pressure side & bingo! Compressor quite cyclingn& is functioning properly!

  6. Im dealing with the same thing. I remove some freon and it stops but it also looses all its cold ait. I only took out a lil bit at a time so is that a bad compressor??

  7. You saved me from taking it to the shop for diagnostic. I was wonderig why my compressor kept cycling. Found your article and it saved me $$$

  8. Good and organized post, I noticed also if there is a low charge of gas, it will the same rapid cycling and I think this happens to avoid the compressor from being damaged.
    Thank you for sharing your post.

  9. Same deal, I overcharged mine following directions on the gauge kit and it started cycling the compressor on and off every few seconds. Vented the refrigerant and the problem seemed to go away. Thanks a lot for your info.

  10. Can the freon be expelled from any side? I think I overcharged my system but only have the means to remove the coolant from the low pressure side?

  11. Expel the Freon on the low pressure side – same side you use to fill it. Just turn the A/C on and you should be good.

  12. Went through the same thing on our 2002 CRV. I added freon, then going down the road it would cycle and pull the engine down very hard. Bled it off, and it seemed to be ok, then took it to the dealer, they drained, refilled with the “correct amount” saying it was a little low, but now it’s cycling and pulling again, enough to be annoying (plus there’s an annoying rattle between 2000-2500 rpm). Took it back and told them what I experienced, so hopefully we can get it resolved.

  13. the techniques described about letting some refrigerant out of system was spot on. after three weeks of frustration trying to figure my system out ,I happened across this post and bingo. it worked for me . thanks guys!

  14. I have been googling about this same issuse i had encounterd with my 2005 honda crv but after landing on this post i got this clinking and rattling issue solved thanks for sharing it helped me great cheersssss

  15. I have a 2006 Honda Accord and was encountering the exact same issue! The AC was not getting cold at all so I added some R-134a. The gauge that came withe the can was still needling at the very bottom so I began adding another can. Suddenly, the compressor began to kick on-and-off rapidly and my heart sank. “Great,” I thought,”I just killed my AC at the beginning of June!” I went for a test drive and sure enough, the AC was not cold at all.
    Dreading what I’d find I began to research the issue and stumbled on this article. Cautiously optimistic I went back out to the garage, started the car, reattached the gauge apparatus, and began to bleed out the system. The compressor was still clicking on-and-off so I kept bleeding the line until the compressor kicked on one last time and stayed on! Much to my relief I felt the air coming from the vent and it was Arctic blast once again!! I bled a little more out for good measure and closed-up shop. A quick lap around the neighborhood confirmed the fix with higher RPMs!
    Thanks so much for saving me an embarrassing trip to the AC guy!

  16. A huge thank you to bsntech, this post saved my butt! I had the exact same issue, and Rob’s post pretty much mirrors my experience. I had a cheap single-gauge kit that only showed the low side pressure. I knew I was running a little low, and ended up adding almost a whole can. It seemed to work ok for a while, then I started to have the same issues. The cheap gauge showed that I was on the low end of operating pressure, so I decided to add a bit more, then the compressor began rapidly cycling, and when it was engaged the engine was almost stalling at idle. I thought for sure I’d be shelling out a hefty sum to replace the compressor. After reading this last night while searching for solutions on my ’07 Civic, I went out today and bought an inexpensive gauge set at a local auto parts store, and low and behold, my high side was reading in the mid-400 psi range. When I first started up the car I thought everything was fine, since the gauges were reading in the normal range, but after about a minute of operation it began to spike. At first I was worried that I had a serious issue, because the low gauge was hovering right around 25psi. I popped off the connecter from the low side and began letting out a little refrigerant at a time, until the high gauge began to drop and the compressor began to stay on. Once I got to a safe pressure on the high side (225-250psi), I reattached the low side gauge. Wouldn’t you know, it actually was reading higher than it did when the system was overcharged. By the time I was done, my low side reads at ~35psi, and the high side ~250psi. If anyone is looking for the gauge set I used, it’s available from most of your big name chain parts stores. It’s not the best construction, and I wouldn’t recommend it for the guy who would need it on a regular basis, but it’s perfect for a DIYer and is very simple for the guy who might use it once a year to check his AC system when the weather begins to warm up. Here’s the link: http://www.oreillyauto.com/site/c/detail/INT0/MF5.oap

    Additionally, just as a precaution, never connect the high-side gauge with the compressor running, you can damage the system, and if you need to bleed off some of the refrigerant, only do so from the low side. Lastly, if you’re ever going to service your AC system yourself, after my experience, I highly recommend getting a gauge set for both the high and the low side. I was fortunate enough not to damage my system, you may not be so lucky.

  17. Hi,

    I just bought one of those ac rechargers at AutoZone. & the AutoZone guy was being nice and helped me add it. Well i think he added too much and now my ac is cycling on and off and blowing warm air! The ac was barely blowing cold air before the recharge and now it blows none. We don’t have the money to buy the gages and i have a feeling that if i just bleed some of the freon it will be fine. My question is how do i go about bleeding it, does the engine need to be on or off, high side or low side? I only intend on bleeding off a small amount to see if it will help! Any suggestions would be appreciated

    • I added a reply to you but not in the proper spot. It is dated 8\22\15. Probably you have the fix by now but maybe someone else….?

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