Automotive Air Conditioning Information Forum (Archives)

RRWA on Fri June 20, 2014 11:43 PM

Year: 2005
Make: Jeep
Model: Liberty
Engine Size: V6-3.7L
Refrigerant Type: R134a
Ambient Temp: 66
Pressure Low: 32-42
Pressure High: 200-310
Country of Origin: United States

Hello everyone,

Background:
2005 Jeep Liberty Sport (KJ)
AC Compressor: Sanden SD7H15 model 4852
Non functioning air conditioning for approx 1-2 years. Clutch would not engage, nothing would happen.
I decided to research the problem. Hooked up gauge set and determined system had 0 pressure in high and low side.
Connected vacuum pump and achieved -20 vacuum. However, it only lasted for 15 seconds after turning off the pump.
Pressurized system with shop air and found gross leak in condenser by spraying soapy water. It was cracked near one of the mounting bracket welds.
Replaced condenser and accumulator(both from Amazon, Spectra brand), and new green gaskets(Autozone).
Added 1 ounce of PAG 46 w/dye (Autozone) to condenser.
Added 2.5 ounces of PAG 46 w/dye(Autozone) to accumulator.
Ran vacuum pump for 30 minutes to approx -29. Vacuum held without any leaks.
Added 22 ounces of R134a.(from Walmart.Straight R134a. 1 full can and 1 partial can). Used digital scale to measure. Label in car says 1.37 pounds of R134a.
I added the R134A as gas to the low side. I put it in a pan of warm water to help speed up the process.

After charging:
Ambient outdoor temperature 66
Humidity 63

Pressure with car off: 74 on both high and low side

Pressure with car on at IDLE, and AC on: Low: cycles from 32-42. High: cycles from 200-310
During this time, the clutch is always engaged.
The electric fan is OFF, until the High pressure reaches 300. Then the fan turns on , and pressure immediately drops to 200. Then the fan turns off. Then the whole cycle repeats. Again, the clutch is always engaged.
Dash vent temperature: 46

My concerns:
1. High side pressure seems too high. I am concerned that at higher ambient temperatures I could blow a hose. These readings exceed the charts I've found online.
2. My dash vent temperature does not seem cold enough.
3. Since the system was broken down for so long, could moisture have corroded and damaged my compressor?
4. Is the fan working correctly?

Notes:
I did not change or even check the orifice tube to see if it was dirty or clogged.
I did not add any "stop leak" products, but who knows what was added in the past by previous owners. The disassembled parts/oil seemed clean and not "gunked up".

Please advise me. I am an amateur at working on AC systems, but I want to learn so that I can do some of the repairs myself.

thanks


Edited: Sat June 21, 2014 at 12:14 AM by RRWA

mk378 on Sat June 21, 2014 7:00 AM

You will see this on any system that cycles the condenser fan. The high side will rise until it is enough to make the fan start. In hot weather, the fan will run more and it should not over-pressure. This is by design, it sounds like you have normal operation. I would suggest waiting to check how well it works in hotter weather.

Also rev the engine to 1500 and see if the low side comes down. Testing at idle won't reach full performance.

Edited: Sat June 21, 2014 at 7:04 AM by mk378

RRWA on Thu June 26, 2014 2:02 AM

After further testing, I determined that the low-speed function was not working in my electric radiator fan.
I replaced it it with a "TYC 621140" from Amazon.

Ambient temp: 72
Before replacing the fan:
Low side: 35-55
High side 250-325
Dash temp 54

After replacing the fan:
Low side: 30-35
High side: stays around 135.
Clutch doesn't cycle very often, compressor runs almost constantly.
Dash temp 46



In summary, I have resolved my excessive high-side pressure problem by replacing my electric radiator fan. This also improved my cooling (lower dash temp).

webbch on Thu June 26, 2014 4:13 AM

Glad you figured out your main problem. Is it just me, or does that dash temp seem a little high for those low side pressures? I'd have thought that 35-40 deg F vent temps should be achievable (when compressor is running). I'd recommend you take a look at the heater control valve to see if it's re-heating the air a bit too much.

Edited: Thu June 26, 2014 at 4:19 AM by webbch

RRWA on Fri June 27, 2014 12:07 AM

You might be right about the reheating. I will do some investigation of this, including clamping off the heater lines and using my infrared thermometer to collect some temperature readings.

webbch on Fri June 27, 2014 1:13 AM

...oh, you're using the infrared thermometer, that may be the issue as well. My experience with them is that they're not very accurate - easily off by 5 or more degrees, a big difference when using for A/C purposes.

Dougflas on Fri June 27, 2014 1:29 AM

Quote
Originally posted by: webbch
...oh, you're using the infrared thermometer, that may be the issue as well. My experience with them is that they're not very accurate - easily off by 5 or more degrees, a big difference when using for A/C purposes.

Exactly correct. For a more accurate reading, the measurement area needs to be painted black.

RRWA on Fri June 27, 2014 6:31 AM

the temperature readings I already posted above were taken using "Robinair 10596 -40 to +160 Degree Fahrenheit Dial Thermometer" which I believe is pretty accurate

I was thinking of using the infrared thermometer to track down the possible reheating problem, but I haven't done this yet.