Need Help Diagnosing A/C Recharge Problem

[MRP78]

I'm trying to recharge the A/C. This is a system that has had new lines, 134 conversion, compressor etc. With everything hooked up and turning on the A/C I hear a click and, change in idle, fan comes on etc., but the compressor doesn't engage. I thought it was just low on freon and I guess it still could be but I'm not sure. Since the compressor wouldn't engage I bypassed the A/C clutch switch, the compressor engages, and the A/C is very cold. The pressure read low and I've added a couple of cans of 134a but the pressure doesn't change and stays right at 25 or a little less. If I hook the clutch switch back up the compressor won't come on. Any ideas?

 

[carolinaturbo]

Did u ohm across cycle/psi switch to see if open or closed? And if closed check volts.

 

[MRP78]

Did u ohm across cycle/psi switch to see if open or closed? And if closed check volts.

Not yet but I can. What am I looking for? If its stuck open or closed what would the ohm meter read?

 

[jopaustu]

On a digital ohm meter. OL is open. 0 is closed. It may very between manufacturers. I've always used Fluke instuments... a continuity tester has an audible tone that indicates a closure... zero ohms indicates closed.. anything over zero indicates resistance (open).. someone has posted a diagram of our Buick a/c circuits before,just can't remember who,where,when. You want a closure on your low pressure swith to run... Joe

 

[TLIMITED]

I'm trying to recharge the A/C. This is a system that has had new lines, 134 conversion, compressor etc. With everything hooked up and turning on the A/C I hear a click and, change in idle, fan comes on etc., but the compressor doesn't engage. I thought it was just low on freon and I guess it still could be but I'm not sure. Since the compressor wouldn't engage I bypassed the A/C clutch switch, the compressor engages, and the A/C is very cold. The pressure read low and I've added a couple of cans of 134a but the pressure doesn't change and stays right at 25 or a little less. If I hook the clutch switch back up the compressor won't come on. Any ideas?

The low side is going to read about 25 which is about perfect.You need to be monitoring the high side also.As far as comp. not coming on I think your low pressure switch is bad if you can cross the contacts at that switch and the comp. comes on.

 

[MRP78]

The low side is going to read about 25 which is about perfect.You need to be monitoring the high side also.As far as comp. not coming on I think your low pressure switch is bad if you can cross the contacts at that switch and the comp. comes on.

Is that the switch on the line right at the compressor? If I have to change any of the switches, the system will lose it's charge right or is there a trick to it? ? ?

 

[TLIMITED]

Is that the switch on the line right at the compressor? If I have to change any of the switches, the system will lose it's charge right or is there a trick to it? ? ?

No the low pressure cycling switch is the one on the dryer.the other is the high pressure switch.It has a valve stem behind it so you will not loose freon.

 

[MRP78]

No the low pressure cycling switch is the one on the dryer.the other is the high pressure switch.It has a valve stem behind it so you will not loose freon.

New $10 cycle switch did the trick.