AC Not Working. Not a Leak? Guru's Needed.

[awesomeissquid]

I have been monitoring some bearing noise from the AC compressor for the past couple years. Regardless of the noise, the AC has always worked well over the last ~6 years. Recently it started not blowing cold. Good kick in the butt to do something about it.

I have assumed there was a leak and been reading threads about testing/possible fixes. Today I went ahead and did some diagnoses and I might be more confused than before. Hoping for some help.


Outside air temp today ~83°F
Static pressures on both sides (engine off): 87psi

• I believe this pressure is expected for the temperature and indicates that my system is not low on charge. But, I cant confirm that without weighing the refrigerant in the system...

Engine running and I started the front and rear AC's
Low side dropped to 15psi, high side went up to 155 psi
Saw lots of bubbles in the sight glass
Small high pressure lines to front and rear AC felt slightly warm, maybe just above body temperature
Front evaporator low pressure line felt cool
Rear evaporator low pressure line felt warm just like the high pressure line.

• Initial reaction here was the low side pressure was pointing to a clog in the system. But why is the rear low pressure line not also feeling cool? I do think the rear fan was on low, so maybe I need to retest that side.

After 7 minutes of runtime the condenser fan started so confirmed that works.
Low side had increased to 25 psi, high side was fluctuating between 217-225 psi.
Inside the ambient temp was around 86°F
Front AC was blowing around 73°F
Rear AC was blowing around 86°F

• Pretty sure I should have seen 30-35 psi on the low side and 200-225 psi on the high side. Again this makes me think about a clog in the system, maybe a stuck TXV.

Continued running the system for ~20 mins and spent the time feeling the lines and checking the internal temperatures.
Felt minimal cooling from front AC, sometimes it would get a bit cooler, other times it felt like no cooling.
Rear AC was putting out almost no cooling at all, again, maybe the rear wasn't performing since the fan was on low?
Saw condensation dripping from front evaporator, nothing from rear one.
Front and rear high pressure lines felt warm all the way back to the condenser
Front low pressure line felt cool.
Rear low pressure line felt warm
High pressure line into the condenser felt hot.


So this is where I am lost.
If I have a bad front TXV, wouldn't the rear still work correctly? Maybe both have failed but that seems odd.
Next thought was since the lines feel the same all the way back to the condenser that maybe that is clogged?

What do I do next?
Should I get a thermocouple on the refrigerant lines to get more exact temperatures?
Should I just start replacing parts?

 

[leveeguy]

Did you check for any codes using the AC diagnostics option? I'm unsure if these attachment's are the most applicable ones for your vehicle.

 

[awesomeissquid]

Good call. Ran through the test and validated that one of my lights is out. Seems I am getting the RrDEF and DEF lights which means either the solar circuit or ac amplifier have an issue.

Need to do some reading on this but since I was testing everything at idle, maybe that is preventing the compressor from working correctly?

 

[leveeguy]

Unsure on the RPM. In case you didn't notice the hints on page DI-630 #3 could pertain to your dtc and possibly help eliminate it

HINT:
*1 If the room temp. is approx. -20°C (-4°F) or lower, RrDEF and FACE indicator may be light up even
though the system is normal.

*2 If the ambient temperature is approx. -50°C (-58°F) or lower, a DTC may be output even though
the system is normal.

*3 If the check is being performed in a dark place, RrDEF and DEF (solar sensor circuit abnormal) could
be light up. In this case, perform DTC check again while shining a light, such as an inspection light,
on the solar sensor. If RrDEF and DEF is still light up, there could be trouble in the solar sensor circuit.

 

[asmara]

Just an diyer but - If you are seeing bubbles in the sight glass you are low on refrigerant. I'd fix that first. If it is too low, some of the safety systems may be kicking in shutting down the compressor.

 

[awesomeissquid]

Tested the DTC again today in the full sun. Still getting the same code and working through the solar sensor circuit troubleshooting steps. I feel this may not be related to my issue since the compressor is engaging and doing some work evident from my gauge readings. Regardless going to work this issue at the same time.

I am going to try adding some refrigerant tomorrow when it is warmer out. Aiming to bring the low side up to 30-35psi and see what happens with the system.

Am I correct in assuming that if the TXV/something else is clogged that I would still not see any improvement in supply temperatures and if I am just low on charge the system should start working correctly?

 

[awesomeissquid]

Did some additional investigation today. Started by adding some refrigerant. System took about 6 ounces.

Front supply went from 74F down to 49F and the rear went from 85F down to 66F. Stopped there since I felt I had confirmed a system leak was likely contributing to my issues.

At 1500 rpm, low pressure was still 27psi and high was right around 200psi. At idle the low pressures rose to 37psi and the high rose to 205psi.

Did some temp readings since the condenser still seemed to be weird. Measured 174F on the inlet and 105F on the outlet pipes. Believe that points to a possible issue with the condenser. Will probably plan to just replace that to be safe since I will have the system open.

Next step will be to get the system evacuated and start disassembly/replacement.