A/C Re-Charge

[xczar]

Original owner of a 1997 YUKON 2dr with 205K miles on it.

When engine runs, compressor kicks in for a second every 10 seconds or so, mild cool air blowing out of A/C.

Figure I can dump a few cans of 134a in there and get`er working properly.

When I hook up the hose gauge to the service port, I get a PSI of 65. When I start up the truck and the compressor cycles on, it drops to 30 PSI.

If the system was low on 132, would not the PSI`s be lower? Maybe my gauge is off or another problem?

 

[OR VietVet]

Your cycling time indicates low on refrigerant. The pressure you list is ok. Add 1 can and see if the temp is good. Would be best to have a full set of gauges to check the pressures on both sides. I will say this though. Do not, I repeat do not add a "FEW" cans of refrigerant. One can at a time but it may only need just the one. Put a thermo in the center dash vent and monitor after adding 1 can. See how far the temp drops. Remember that the temp will be a little higher at high fan speed because of fan turbulence. The lower fan speed will blow colder. That is why when you first turn on the a/c you have on high to get the heat gone and then drop the fan speed for the colder maintained temp.

 

[xczar]

Yes, adding several cans now is my concern.

My gauge reads:

10 - 15 psi = low
15 - 45 psi = full
45 - 65 psi = alert
65 - 100+ psi = danger

So I am worried about the initial 65 lbs I am reading before I put anything in there. But, if it were that full, why am I not getting cold air? Plus, as one adds coolant, how does the system exhaust any air or whatever in the lines?

Appreciate your thoughts.

 

[OR VietVet]

Pay attention to the pressure when the clutch is engaged. The pressure when the clutch is not engaged is called static pressure.

 

[xczar]

Got one can in there. Took about 5 minutes or so. Compressor gradually stayed on longer to about 4-5 seconds every 15 seconds. The PSI with the compressor going went up to 45 psi and pretty much stayed the same with it off at 65 psi.

Air temp noticeably cooler. Guess I`ll wait until a warm day to see how good it works before I try another can or something.

 

[OR VietVet]

Ok, so now is better. Remember what I said about the low fan speed after the original heat is pulled out of the cab. Adding too much R134A is bad for the compressor. Monitor it all and let us know. Will also cool better when driving because the heat dissipates better at the condenser moving thru the air.

 

[xczar]

Thanks Ron for the advise:

I still am a bit concerned about the warnings on my gauge. If I originally had 65 lbs before I added anything, why was my A/C not cold to begin with? After adding one can, why is it still 65 lbs? With the compressor going, it is at 45 lbs (from 30 lbs. before the added can).

Also, what is considered normal cycling for the compressor? How long is it supposed to kick on for and what intervals?

 

[OR VietVet]

As I stated earlier the 65 psi reading is static, with the compressor not engaged. The compressor clutch engaged and reading 45 psi is way better and indicates a likely full or close to full system. The cycling time can vary depending on ambient temp and humidity. Just drive the damn thing and report back how it feels. Those readings you laid out with the warnings are all related to when the compressor clutch is engaged.

 

[xczar]

Just trying to fully understand the dynamics of this. Thanks for your input. Just don't call my truck "damn thing".