I bought one of those recharge cans with the gauge but not sure if I'm supposed to read it when the compressor is engaged or not spinning. It reads good when the compressor is not locked but then shows low when it is running. Should I bring the level up to the correct level with the compressor running?

 

The Engine should be running with the a/c on max a/c and fan on high... then it should be checked and filled as necessary. if the compressor clutch kicks on and off rapidly then the system needs more... also turn the can upside down when filling to get the liquid.... Hope this helps...

 

I have a chart that i use and is based on 134a and ambient temperatures.
All low side.
65 degrees outside. 25-35psi
70 degrees outside. 35-40psi
80 degrees outside. 40-50psi
90 degrees outside. 45-55psi
100 degrees outside. 50-55psi

When i do the cars/trucks. It is usually because i want better ac. So it is 70-90 degrees. So i shoot for 45psi. And i get great ac. I stick a meat cooker meter in my ductwork. To Check. I am at 43psi now in my truck. Yesterday it was 88 degrees. I was blowing 45degrees. Like said Aaron. Everything on/Temp Cold. Fan on high. Running. Can upside down. Piece of cake. If it is cycling on/off when you first start it. Means usually it is low. After you put in a can it should run constant. Pump running all the time. PSI is for pump running.

 

just like Aaron said..the clutch un locks cause its low on freon..when you start filling it the clutch will stay lock when enough freon is in... then go by the reading on the gauge.....

 

Thanks for the info. It looks like it needs more juice. On my car it cycles on and off and doesn't get very cold. On the truck it stays on but is not very cold even with the A/C mod. It reads low when the compressor is running and I gave it a shot but I had the can upright, I'll turn it upside down and bring the level up tomorrow and see how she runs. Neither have ever had any work done on them and have over 100K on them.

 

How long does freon last? Does it degrade over time?

My truck has 145k on it and I also have noticed it isnt as cold as it used to be. Im going to hit the auto parts store tomorrow and buy a gauge and freon to test it.

 

You can get the hose with the gauge on it at walmart and the cans a bit cheaper. Get the regular 134a. Not the stuff with additive(oil,UV.etc). If you outside are temp in your are is between 70-80 degrees. Get her up to 40psi 'ish and you should be golden. The gauge comes with color charts and PSI on them, built in. I don't pay attention to it. I go by PSI because the color chart don't know what the ambient temperature is. If warmer than 80degrees. Go 45-50psi. Don't go to much over that. Over fill is bad to.

My Focus a couple weeks ago on a 85degree day was cycling on and off when we first turned everything on. I tossed on the gauge. It would rise when the pump was on to 40psi then bleed down to 15 then the pump would turn off. It would repeat this cycle over and over. I put in a can. It came on and stayed on. Held at 30psi steady. Got 60degrees blowing. Put a couple more cans. (i forget how many) To get to 45psi. The temp dropped to 45degrees blowing. At Idle. Went for a ride at speed and the temp dropped another 5 to 40 degrees. Wife was pleased and frozen. My truck has been good. Tossed the gauge on that to see what it was at and it read 43psi. So i left the truck as is.

Not sure if freon degrades. Doubt it. But the systems leak a bit. In a real world they shouldn't. But They do. I believe out the pump seal. My wifes Focus is a 04 with 45k miles on it. My truck just turned 80k

I think cans at Wally world is 4.97 a piece. I can't remember what the hose cost me. It was a few years ago. And i think my hose came with a taller and larger can. We should be clipping in to the high pressure side to get the difference on the high pressure. But i have never bothered with high pressure auto's. I just tossed on the cheap gauge and pumped them up and forget about it till next year. If it don't last a season. Then you have other leak issues. Just did my neighbors car Sunday. They called Monday said it was working good. They are going to take me to dinner. Not to shabby, I only put in 2 cans to get it to 40psi'ish.

The Meat cook temperature gauge i got at wegmans. $8. I just placed it in the vent. It stays there unless i am cooking on the grill. You can see it in this picture i took for another thread about removing a cover. But the gauge is visible.
http://i233.photobucket.com/albums/e...kool/COVER.jpg

 

Another way to tell if there is enough freon in the system is to check the temperature of the evaporator core inlet and outlet pipes. The inlet pipe will be the cooler until there is enough added to fill the system. When there is enough freon, both pipes will be at nearly the same temperature. I check this by feel, but I do also like to check the pressures to prevent an overcharge.

 

In my experience this is very bad advice unless you want to buy a new compressor soon. Too much liquid all at once can and will seize the compressor. You want the gas in there, not the liquid being compressed. If you want to get it in quicker put the can in a pan of hot water right side up and keep on adding cans until the compressor clutch stays engaged long enough to cool the cab. In other words not cycling on and off constantly without being cool inside already. Doing the cycling and still blowing hot is the low pressure switch on the compressor doing its job of protecting the compressor from running without enough freon.

 

This is especially true when the charge port is directly mounted on the a/c compressor. The compressor doesn't like to compress liquid ( same goes for our diesel engines). The a/c system is designed for a low pressure gas to be entering the compressor inlet during operation.

 

True. But i think we survive by the tiny hole that is popped in the can, the check valve in the hose the hose connectors and the shradder valve all acting as a orfice. Plus i regulate the the t connector to about 90 psi to not bottom out my gauge. Just cracked open. All that is the reason i believe i have done more cars than i can count for 20 years with r12 and 134. And never had a compressor failure. Not dissagreeing to what you saying, Because your right. But highly doubtfull with the cheap hoses we buy for the DIY'rs. I have hoses and tank that would for sure cause problems. But i like the the cheap hose/wgauge and small cans. Fast and simple and easy to charge my friends and family for the gas i put in. Because i know exactly how much went in and i show them how to do it so they don't come to me anymore.

 

Not doubting your abilities. Just that the average DIY'er needs to be informed that you don't just "throw a few a cans in there" to make an a/c cool. It's good that you show your friends and family the proper way to do it.