So I noticed a while back the performance of the system was going downhill...been working 7 days a week for a while and just didn't have the gumption to deal with it.

a few days ago I was checking the mail and noticed the compressor struggling and felt it was time as I was worried about any damage that might be occurring with low refrigerant levels...compressor was constantly cycling off and on...

anyway, I picked up a 20 oz can of 134a and emptied it into the system this morning...at first the pressure was fluctuating all over the place...compressor would kick in and it would drop way low, then turn off and it would climb to about 45 (whatever the units) then turn on and drop again...the higher reading fell within the temperature adjusted allowable range...as the 134a was fed into the system this eventually went away and as the can got emptied the pressure was holding at about 27...the air is blowing probably colder than it did from the factory, but that was a long time ago and the real test I guess is driving home with temps above 100* and traffic...

point being, should I get another can (12 oz I guess) and top it off?

from what I've read here and there this system should hold around 33 oz of the stuff...hmmmm...

while I'm no n00b I am certainly not well versed in this stuff...I've recharged 2 other vehicles in my life...a '86 t-bird and a '89 volvo...both of those filled up with a 12 oz can and gave expected pressure readings...yeah, I'm a DYI person who bought a can with the gauge that only reads the low side...

one final note: the can of 134a acted empty...no longer was condensing water on the outside...followed instructions and turned it upside down for 1 minute...but upon taking the cap with gauge off some came out...about 1 oz methinks...

I'm guessing the residual pressure in the can was insufficient to shoot the refrigerant into the system...yeah, guessing...

hence my making this post.

thanks in advance for any advice (other than taking to a professional...don't have the funds or time for such a thing at this moment)

 

further information that might be relevant...

the only times I ever hear the compressor running are when I'm checking the mail...that's because I leave the engine running and am a few feet away...

from what I've read the compressor should be running constantly when on the max a/c setting...and that is occurring now...

at a molecular level it is expected for r134a to slowly leak out of the system via the rubber hoses and gaskets...the thing rolled off the assembly line in April 2007 so I'm not surprised at the results over 8 1/3 years!

what I noticed a few days ago was the cycling occurring every 5 seconds...and it sounded rather weak/struggled...that time information might be useful to somebody who knows their stuff in regards to my query about what low pressure reading I'm getting and its relation to having put in about 19 oz. of r134a and that relation to how much was actually in the system before I recharged...

on a related subject, is it normal for some AC to come through the defrost vents also? annoying as it creates condensation on the outside of the windshield when it's humid...

thx

 

No, unless the load on the system is such that 100% duty cycle is required.

Yes. Turn the temperature up a bit until the condensation stops.

 

If the system has enough refrigerant, the compressor should stay on most of the time at idle. If that is the case and it is cooling ok, I'd leave it alone. Without measuring the discharge pressure, you are flying a little blind. You don't want to overcharge it.

 

Yes, but ONLY if the sensing and control systems are working properly, as well as the electro-mechanical portion of the system.

The control system is complex and includes the EATC, the instrument cluster, and the PCM. Trying to diagnose those system components as a DIYer without the proper training, equipment, and documentation is a shot in the dark.

 

thanks guys...

I would have to say at this time, just having gotten home from work and making a 1/2 hr. drive in 100+* that it cools about like it did when I first got it in...sure, it's cold in the morning (80*) but struggles to really cool when it's hot as Hades out!

I'll leave it alone until at least Sunday (my one day off...not sure what to believe about all things related to recharging an AC, but I intuitively agree with the concept you shouldn't do it if it's above 85* or so) and then only after having checked the pressure to see if it's the same...

yes, the compressor is constantly running at idle...don't know of any way to really determine if it's shutting off when under load (and by that I assume it's something like flooring it to merge into traffic or bogging down the engine going up a hill because the idiots in front of you are doing 50 in a 65 zone with no real traffic to justify it (deal with that just about every d*mned day) as the truck is pretty quiet inside (though loud music being played in the cabin surely is loud outside of the thing!)

and yes, I am quite aware of the 'concept' of the fact modern vehicles are computer controlled and without the proper equipment I am very limited in what I can diagnose.

what I do know has already been described...noticed the compressor clicking on and off repeatedly last Thursday...run about 1.5 seconds, then cut off...then less than five seconds later repeat...and sounded like it was struggling...discharging an entire 20 oz. can of r134a took a while, and over the time it was going into the system the cycling times got further apart and compressor running was longer and longer until it stayed on...at the time the can stopped condensing (indicating to me it was discharged...and I no longer felt anything slushing around when I shook it gently) the indicated pressure was around 27 psi. I don't have enough experience with such things to make ANY sort of estimate of how much refrigerant was left in the system (but there must have been some as the compressor was still kicking in????)...

valid points are made out the high side reading and how it would relate to it all I guess...I would 'think' the stated low side reading of an ideal 35psi at 70* or so would hold water, but what do I know

so let's say I do get another can...12 oz. and expect to use 1/2 of it to get the stated amount of product the system holds as written on the cowl above the fan...can I expect to see the pressure rise from 27 to 35 pretty quickly (indicating it is correct to top off and not exceed the amount intended for the system)?

 

There are too many variables and unknowns for me to just say yes to those last questions. When you charge it what is the temp outside? Heat load inside your truck? Is the condenser coil clean? High side pressure? While yes you COUD go strictly off the low side pressure and PROBABLY be OK... That's not always the case. Something else could be going on. Could be a restriction somewhere that's finally letting more past with the freon you added but the high side pressures could be crazy high. Or because I'm an ac tech I could be over thinking it lol. Give it a try n see what's up.

 

Does anyone have any more input on this old thread?

My '06 a/c compressor is cycling every 5 seconds also.

 

What input do you want?

You haven't provided enough for any opinion to be formed. Compressor short-cycling is usually the result of a low charge, but not always.

 

Good point.

Last summer, it was cycling often, but not every 5 seconds. I tried to add refrigerant, but it wouldn't take. The single gauge on the can indicated pressure was too high.

The air has been blowing warmer for the past few months.
This week, it is now cycling every 5 seconds.

I haven't found a set of real HVAC gauges to diagnose anything, though.

 

Dumb question. But, when you tried to charge it, you did have the engine/AC running, didn't you?

 

It was likely misinterpreted or misunderstood.

Those would be helpful....

 

Yes sir!
The system accepted some of the can, but not all.
It has been over a year since I tried to refill it, so I need to do it again.
And I understand that it's a closed system and it should not be low on refrigerant, I"m just trying to diagnose and address as much as I can before I start replacing parts.

 

It takes heat to vaporize the refrigerant. It takes a while for that to happen. I always set the can in a pot of hot water to speed up the vaporization.

 

At this time of year, about 20 minutes in the sun will do it...