Hi guys,

I am a complete neophyte. I am trying to recharge my AC system. I'm pretty sure I found the low side port and attached the can with my recharge kit. It only took a small amount and then quit. There is still lots of R134 in the can. The AC does seem cooler to my hand, although it is evening here and not much heat. I don't have a reliable thermometer. The pressure guage on my recharge kit reads 35 to 45. My compresser thingy, the one that spins where I can see it on the fan belt path, spins for 9 seconds and shuts off for 2 seconds. Is that normal?

Thanks.

Val

 

Sounds like a low charge.of 134A. BIG MIKE

 

It's too difficult to tell how your system is doing with that info.

If you're running the A/C in San Diego in the evening when it isn't hot then yes, the A/C clutch will cycle off and on more often than on a hot day because it doesn't need to work as hard to get the heat out of the system. However, 9 seconds on/2 seconds off doesn't sound quite right. What setting did you have the A/C fan on? Low? High? The lower the fan speed, the more the A/C clutch will cycle because of the same reason above, it isn't removing as much heat.

The A/C clutch will also cycle because of an overcharge too but your 35 to 45 actually sounds pretty close to the normal range for the low side. I'm just a backyard mechanic when it comes to A/C service and without looking it up those pressures seem close to normal.

If you really want to know if your system is charged OK you need to get a set of gauges so you can monitor the low side and high side and then compare those readings to a temp/pressure chart.

 

thanks guys. I had the AC on Max. High. It seems to be much cooler in the cab now, so what ever amount went in must have been correct.

Val

 

Well, I got one of those self recharge kits with guages and from what it found 35-45 PSI low side is normal for R-134a systems (According to the guage supplied with the kit).

Still my A/C compressor cycles on / off. The pressure will go down to about 32-35 PSI and hang and then cycle off and rise...

I think that DC added a temp sensor to the A/C so when it hits a preset limit of temp it will cycle the compressor to save on fuel or to keep it from freezing up.

When you start getting below 25 PSI (somewhere around there) you will see the compressor shut down for safety. But the A/C will feel quite warm!

I hope this helps...

 

When you charge auto A/C units, you should run system on max cool (recirc), with fan on high and the windows or doors wide open (especially the passenger door). ALWAYS put refrigerant into the LOW side and NEVER invert the filling can upside down. The compressor should not cycle with the door open. If you fill with the can in the upright position the charge will take quite a while to go in as the refrigerant in the can flashes off into the system (this is why can gets cold). To help expedite the process of getting the gas to go into the system a little quicker, place the can, upright into a pan of HOT tap water. This process will raise the pressure of the gas in the can and force it into the A/C system faster. Place a thermometer into the center vents of the A/C system and look for a discharge air temp of 40-45 degrees F.. This should get you "in the range" of a full charge.

Good Luck,

Gary

 

"To help expedite the process of getting the gas to go into the system a little quicker, place the can, upright into a pan of HOT tap water. "

Thanks for the tip... I'll try this and see if I get a bit more in there. I wonder if I do it on a very hot afternoon if it will take a bit more. I think maybe I was just impatient. I didn't realize it would take a while. Since it was under pressure and there are so many warnings on the can I figured it would blast in there and I'd have to scramble to get it shut off before I overcharged the system and blew myself up.

Val

 

Nahhh, as soon asy you start up the truck with the a/c running, the pressure in the low side goes down to 45 psi.... The can with sitting in 110 degree water will have about 140 psi on it, but will rapidly drop in pressure as the refrigerant flows out. The reason the can gets cold is that the pin hole the piercing valve on your can tap creates, acts like the metering device on your coil. Another nifty little thing to look for is a lot of condensation dripping off of the suction line where it goes into the compressor. If it is even lightly humid outside, when the system is close to full charge the suction line will sweat like a nervous husband to be @ a shotgun wedding.

Good luck again,

Gary

 

I like that one!

But your right it should be sweating like mad... There should be NO ICE on the lines! That is a sign of low pressure / freon.