Automotive Air Conditioning Information Forum

I noticed on idle my ac compressor keeps cycling on/off every 5 secs. It does blow cold air but I guess not like it used too. I hooked up gauge on low side and the pressure goes from 30 to 40 back and forth every 5 secs.

Is it low or overcharged because it‘s still in the “FILLED” area when the compressor turns on at 40psi and off at 30psi. Or maybe bad switch

I have video as well
2019 Durango

https://www.dropbox.com/s/hj20yca38s6rs ... M.mov?dl=0

Does your vehicle take the new R-1234yf refrigerant (check the under-hood decal), and is it still under warranty? If yes to both questions, I would take it back to the dealer and let them recover and weigh the existing charge. If it's low, have them recharge it to specs and then leak-check the system using an electronic leak detector.

Those single-guage discount kits are worthless for proper diagnosis.

JohnHere wrote: ↑Thu May 05, 2022 9:46 am Does your vehicle take the new R-1234yf refrigerant (check the under-hood decal), and is it still under warranty? If yes to both questions, I would take it back to the dealer and let them recover and weigh the existing charge. If it's low, have them recharge it to specs and then leak-check the system using an electronic leak detector.

Car warranty expired last month and yes it does take 1234yf.
I just hooked up the gauge again and now it’s doing it every 15secs.

The car did have the front end repaired a year ago with new parts and before that it was brand new without this issue.

Tim wrote: ↑Thu May 05, 2022 9:59 am Those single-guage discount kits are worthless for proper diagnosis.

I figured but I’m just trying to get an idea of what’s going without buying real gauges and 1234yf since it’s pricey.

If the car is out of warranty, you will end up taking it to a first class AC repair shop. Fixing a 1234yf system is rather beyond the capability of a do-it-yourself project. The exact amount of refrigerant must be weighed in, to the ounce, else it will just not work correctly.

Be sure the shop has MACS certified signs. The MACS certified guys are the only ones who know what they are doing. Skip the muffler shop that has a sign, "we fix AC"

Did the collision shop have any kind of warranty? For example, around here, Caliber Collision has a lifetime warranty. It would seem the AC repair was perhaps not the best

Najeem wrote: ↑Thu May 05, 2022 10:39 am Car warranty expired last month and yes it does take 1234yf.
I just hooked up the gauge again and now it’s doing it every 15secs.
The car did have the front end repaired a year ago with new parts and before that it was brand new without this issue.

A stroke of "un-luck" in that the warranty expired recently. My educated guess is that it's a bit low on refrigerant, though.

You didn't explicitly say, but was the front-end repair due to collision damage? If so, do you recall whether the shop replaced the A/C condenser? If the answer is no, the original condenser could have suffered slight, unnoticed impact damage that caused a very slow leak, and it's only now showing up in the form of rapid compressor cycling and compromised cooling due to loss of refrigerant. Member tbirdtbird has offered some good advice. You might have to take it to a professional A/C shop to deal with the problem.

Najeem wrote: ↑Thu May 05, 2022 10:40 am I figured but I’m just trying to get an idea of what’s going without buying real gauges and 1234yf since it’s pricey.

Pricey is right. We're all hoping that the costs of R-1234yf and the associated equipment go down over time. That hope might turn out to be a pipe dream, though.

JohnHere wrote: ↑Thu May 05, 2022 11:23 am

Najeem wrote: ↑Thu May 05, 2022 10:39 am Car warranty expired last month and yes it does take 1234yf.
I just hooked up the gauge again and now it’s doing it every 15secs.
The car did have the front end repaired a year ago with new parts and before that it was brand new without this issue.

A stroke of "un-luck" in that the warranty expired recently. My educated guess is that it's a bit low on refrigerant, though.

You didn't explicitly say, but was the front-end repair due to collision damage? If so, do you recall whether the shop replaced the A/C condenser? If the answer is no, the original condenser could have suffered slight, unnoticed impact damage that caused a very slow leak, and it's only now showing up in the form of rapid compressor cycling and compromised cooling due to loss of refrigerant. Member tbirdtbird has offered some good advice. You might have to take it to a professional A/C shop to deal with the problem.

Najeem wrote: ↑Thu May 05, 2022 10:40 am I figured but I’m just trying to get an idea of what’s going without buying real gauges and 1234yf since it’s pricey.

Pricey is right. We're all hoping that the costs of R-1234yf and the associated equipment go down over time. That hope might turn out to be a pipe dream, though.

AC condenser was not damaged but I'm sure the line were. I was shocked when I saw how much 1234yf was lol

I put another video and it's still doing the same but about 15 secs cycle. I might just buy one can and add some freon see how it goes.

To my understanding if it was low the psi should drop under 30 when compressor is on but mine gets to 35 then turns off up until about 42 so isn't that fully filled?

Thank you for ur help btw

https://www.dropbox.com/s/q80d8v46ypeil ... M.mov?dl=0

It sure seems like a leak, and at $80.00 per can, 1234yf is nothing to waste. You'll go broke constantly installing cans of 1234 if the leak is not located and fixed. Is your compressor a variable stroke compressor?

"To my understanding if it was low the psi should drop under 30 when compressor is on but mine gets to 35 then turns off up until about 42 so isn't that fully filled?"
This is not how it works.
Not sure you are getting the drift of things here, a modern system such as yours CANNOT be charged by pressures. The 1234 must be weighed into an empty system after the leak is repaired

Najeem wrote: ↑Thu May 05, 2022 12:47 pm AC condenser was not damaged but I'm sure the line were. I was shocked when I saw how much 1234yf was lol

Do you recall whether the shop replaced the line?
Most people are unaware of how much R-1234yf costs in the current market. Honeywell Solstice, the originally developed refrigerant, comes in an 8-ounce can. That's right...we don't even get 12-ounce cans for our hard-earned money anymore.

Najeem wrote: ↑Thu May 05, 2022 12:47 pm I put another video and it's still doing the same but about 15 secs cycle. I might just buy one can and add some freon see how it goes.

That's actually close-to-normal cycling behavior on the low side for an R-1234yf system, although the pressures are a little elevated IMHO. Presuming the gauge you have is accurate (it probably isn't, though, as pointed out earlier), and taking that into account, the indicated pressure rises to 40 PSI where the compressor engages, and it drops to 34 PSI where the compressor shuts off. Those pressures correspond to an evaporator temperature of 41F and 36F respectively.

Although we don't know what the high side is doing, I like to see low-side pressures on an R-1234yf system a touch lower than that—37 PSI (compressor "on" at evap temp of 37-38F) and 32 PSI (compressor "off" at evap temp of 32-33F). So it does appear to me that the system is slightly undercharged.

It's particularly difficult to "top up" these systems because of the fact that they hold so little refrigerant. It's not like the "old days" where close is good enough. If the charge amount is off as little as 1/2 ounce, performance will likely be compromised. So bear that in mind. The best way to recharge is to recover what's in there now and then recharge to the exact amount called for on the under-hood decal. A competent A/C shop can handle that for you.

Najeem wrote: ↑Thu May 05, 2022 12:47 pm To my understanding if it was low the psi should drop under 30 when compressor is on but mine gets to 35 then turns off up until about 42 so isn't that fully filled?

Not necessarily. The pressures, which can give us clues about performance issues, don't indicate the actual amount of refrigerant in a system. Only the weight of the refrigerant inside the system does. It seems to me that the system is a bit low on charge as I mentioned earlier.