Calling all Auto A/C gurus!

[Boomyal]

I bought myself an 18 oz can of R134 at Wally World for $23, It came with a gauge and hose. This morning I went out and started the 2006 Explorer up and turned the air on to it lowest temperature setting. I also turned the fan on high. The outside temperature was 76?.

I immediately noticed that the compressor was cycling on and off every few seconds. I thought that to be odd. I hooked the pressure gauge up to the low pressure port and every time the compressor cycled the pressure would go from about 15 lbs (off) to 55 lbs (on) It did this repeatedly. I left the gauge hooked up and turned off the A/C. The pressure went up in the red to about 100 lbs. I did not leave the gauge on long to see if that pressure dissapated.

What could be going on? There should have been no reason for the compressor to be recycling every few seconds. I had the doors open and the temperature set at 60?. I have only owned the vehicle for 1 1/2 years and have no way of knowing if it had ever been charged before. Also when the compressor cycled on the gauge would go up to 55, sometimes 58? (still in the green range) which was higher than the chart said it should for the ambient temperature.

 

[gm280]

I've seen that happen lots of time. Are you saying that when the pressure was 15psi the compressor would turn on? Because that seems backwards. Once the low side pressure drops to a certain level the low pressure switch opens and stops the compressor from running so you don't run it with an empty system. It really sounds like it needs more Freon to keep it running properly. And once the system is turn off, the pressure equalizes in the entire system so a higher pressure in the low pressure side is normal. However, once the compressor starts running then the low side drops and the high side goes up. And I think that is what you are seeing. You have 55psi when the compressor is off and the system starts to equalize and then the low pressure switches close because the pressure is high enough and that starts the compressor again. And then that sucks the low pressure side back down to 15psi and it turns off again. That IS where the cycling is coming from. You need to add more Freon until it stops cycling... JMHO!

 

[Boomyal]

I may have gotten it backward, gm280. I looked down to see the clutch and could not find it so I guess I may have guessed wrong about when the compressor was engaged. I'll go back out and find the clutch face and try it all again to verify it is as you say. I don't use the A/C all that much but it did not seem a cold as it should have been. What you say could certainly cause that. Also I do not have a high side gauge so I am only going by the low side.

I'll report back.

 

[Boomyal]

It's as you say, gm280. When the compressor kicks in, the pressure drops to 15 psi. I'll await your word of confirmation before I screw the bottle on and pull the trigger. It is now about 80? out and the chart says to fill it to between 40 and 50 psi.

...and incidently, the A/C off pressure did not drop in the several hours since the last test. It was still around 100 psi.

 

[gm280]

It's as you say, gm280. When the compressor kicks in, the pressure drops to 15 psi. I'll await your word of confirmation before I screw the bottle on and pull the trigger. It is now about 80? out and the chart says to fill it to between 40 and 50 psi.

...and incidently, the A/C off pressure did not drop in the several hours since the last test. It was still around 100 psi.

Yes that is what I thought was happening. You need more Freon to stop the cycling. Once it has enough, the low pressure side won't drop low enough for the compressor to stop again... Post back and let us know how it works out... :thumb:

 

[alldodge]

Here is your pressure chart. If your at 76 degrees you should have 35-45 psi on the low side while the compressor is running. Keep in mind this is approxament and keeping it a bit on the low side is better then the high side.

 

[Boomyal]

OK, partial success. I used the whole 18 oz can but it only got it up to 35 psi. I've not done this before so I do not now how to judge. It took it pretty slowly and soon after I started the compressor quit cycling. Although the can feels empty there is still a little residual pressure in it after I disconnected it and pulled the trigger. Also the hose is pretty short so it made it cumbersome to keep moving the can from the 12 o'clock to the 3 o'clock position. Near the end I just turned the can upside down and kept wagging it back and forth.

I'll go down and pick up a couple of 12 oz cans and try to add some more. The chart said at 80? ambient temp to run it up to between 40 and 50 psi. Even at the 35 psi the air is blowing noticeably colder in the cab. Every thing seems to work well so likely this has never been re-charged in its 9 years of existence.

 

[alldodge]

Could be you now have a slow leak, and may need to add a bit every so often. If you have to add quite often let the Freon go low. When it starts doing what it was doing today, get a can of 134a with sealant. Turn can upside down and add the can, this is why you want it to be low. As you add release the trigger every couple seconds and watch the gauge, don't want to over fill. The sealant will stop small leaks, if it does not then you will need more professional service as in maybe an evaporator core replacement

 

[bruceb58]

Personally, I would not put a sealant in there. Take it to an AC guy that has a leak detector. Could be something as small as an o-ring on a connection. Most AC techs will not work on a system that has stop leak put in them.

 

[alldodge]

Most AC techs will not work on a system that has stop leak put in them

Never ran into that issue, is this something that has started to happen recently?

 

[bruceb58]

Never ran into that issue, is this something that has started to happen recently?

If the tech uses a refrigerant recovery system, which licensed techs are supposed to use, they can't recover the refrigerant.

 

[alldodge]

Still, same issue , I'm unable to find where someone which works on an AC systems for a living will not work on one with sealant

 

[Boomyal]

Well I picked up a couple of 12oz cans and will get it up to the 45 lbs it should be at. Then it is easy to install the gauge and check it down the line. My feeling is that it had never been checked in its 9 years. It still blew pretty cool and you could not discern that the compressor was cycling on and off from the cab.

 

[bruceb58]

Still, same issue , I'm unable to find where someone which works on an AC systems for a living will not work on one with sealant

Give them a call and find out for yourself. My brother is a used car dealer and he deals with this issue all the time.

This is an interesting article that talks about some pros and cons
http://www.imcool.com/articles/aircondition/ac_sealants_p2.php

 

[TCATTC]

You need to have a set of manifold gauges hooked up to charge your system. The high side pressure is important too and you could blow a hose if overcharged.

 

[Boomyal]

In the end the system was a little less than half empty. It is a front and rear air system and takes a total of about 47 ounces. I used one full 18 oz can and about half of a 12 oz can to get it up to spec pressure for the ambient temperature.

It was interesting when I started the car and turned on the air this morning in preparation for topping it off. Initially the compressor started cycling on and off again, with pressures (like yesterday) swinging between 15 ish and 55 ish. Very soon though, the compressor quit cycling and the low side pressure stabilized at 25 psi. I then used the new 12 oz can to run it up to the high side pressure range for the ambient outside temperature.

In a couple of weeks I will recheck it and if things have changed I will have it professionally looked at.

Thanks for all the help!

 

[gm280]

In the end the system was a little less than half empty. It is a front and rear air system and takes a total of about 47 ounces. I used one full 18 oz can and about half of a 12 oz can to get it up to spec pressure for the ambient temperature.

It was interesting when I started the car and turned on the air this morning in preparation for topping it off. Initially the compressor started cycling on and off again, with pressures (like yesterday) swinging between 15 ish and 55 ish. Very soon though, the compressor quit cycling and the low side pressure stabilized at 25 psi. I then used the new 12 oz can to run it up to the high side pressure range for the ambient outside temperature.

In a couple of weeks I will recheck it and if things have changed I will have it professionally looked at.

Thanks for all the help!

Okay, sounds like you did it correct. Once you really understand how they operate, it really isn't that mysterious and easy to do repairs and draw down a vacuum and refills too. Post back when you check it again... :thumb:

 

[Boomyal]

Okay, sounds like you did it correct. Once you really understand how they operate, it really isn't that mysterious and easy to do repairs and draw down a vacuum and refills too. Post back when you check it again... :thumb:

Do you think that my old '65 Mustang Convertible, with factory air (york compressor), has a low pressure switch in it? I haven't charged it since 1982ish and it still blows cool. I think it could use some freon, though. I have a couple of cans of R12 kicking around. I like to run it every now and again just to keep things lubricated.

I like the fact that the Explorer had Schrader valves for both the high and low pressure ports. My '94 Suburban had a cheap plastic low pressure valve that started leaking all on it's own. A friend with a '99 suburban had the same valve and it also leaked on it's own.

 

[Tim Frank]

Give them a call and find out for yourself. My brother is a used car dealer and he deals with this issue all the time.

This is an interesting article that talks about some pros and cons
http://www.imcool.com/articles/aircondition/ac_sealants_p2.php

It's not a lot different from using a stop-leak compound in a cooling system instead of fixing the problem properly.
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