I am having some issues with my AC. Initially it was not working. Shop confirmed pressures, no leak, identified that the compressor was dead. Replaced compressor, refill. AC was "working" but very weak. Shop was not happy with repair as AC was not getting as cold as they would like.
Came back to replace accumulator, expansion valve. Refill. AC continued to be weak. They could not solve the issue. noted that the compressor was cycling every 5-10 seconds. Thought that somehow the condenser was blocked?
Shop replaced condenser, no change, still weak. Shop not sure what to do.
While it was not working "great:" I was able to keep it fairly comfortable in the cabin....until the ambient air temp became higher than say 76 degrees, then the AC only blew warm-hot air...no cooling...compressor not engaged. When ambient dropped back below say 72-74 the AC would begin to work, but not well...weak as it was before, but it was cooling some.
I replaced the outside ambient temp sensor, no change.
I replaced the AC pressure sensor, no change.
I replaced the cabin temp sensor, no change.
Not sure where to go at this point...and ideas?
I hooked it up to ForScan and got this data if it helps....




Pressure continue to rise, compressor shuts off for high pressure, pressure slowly falls, hits "normal range" and compressor turns back on, pressure rises, then shuts off...
This cycle continues over and over. I tried to post a video but I could not get it to upload.
Any ideas?

 

Anyone bother to connect a set of gauges? If so, how did they behave?

 

shop has vacuumed and filled it multiple times and claims that it is set to spec and not leaking. They claim that the pressure was within spec. They did note that the high would spike and come back down but were not sure on cause?
I have not seen it myself but that is what they are telling me.

Also I am trying to figure out what "Driver WOT" means in the second picture. Those photos are from a 30 second video I took with the vehicle at idle.

 

You need to use gauges in conjunction with the PCM data.

 

ok. I will get gauges tomorrow. What should I do with them? What readings are we looking for?

 

BTW:
1. Is the engine cooling fan operating when the A/C system is activated?
2. Did you scan the PCM and the HVAC module for any DTCs? Especially, anything related to the APP (Accelerator Pedal Position) sensors?

Connect them to the system. Verify static pressure per R134a pressure/temperature chart. Start engine. Turn on AC. Watch gauges, preferably record them as a video as the system cycles. Observe and compare the ACP_PRESS PID to the high side gauge to see if they correlate closely. Turn off system. Watch/record how long it takes for the pressures to equalize at their static level.

Report results. Include ambient conditions.

 

ok sorry for the delay. I got some gauges. I have more data for you guys. Problem has been that I was waiting for hte outside temp to rise above say 80 to test when it was having that over pressure situation. The temps are supposed to rise in the next few days and I can post more data if neccessary. Here is what I have thus far:
1. Yes cooling fan is operating. grill is open.
2. NO DTC present. APP report no error. I drove with the live data running and I did not see any unexpected "spike" in voltage or throttle position to indicate an errant WOT condition.
3. connecting gauges and comparing to live data pressures shows the pressure within approx 30 PSI
4. with system off engine off it takes approx 15 min for pressures to equalize on gauges.

With system running at 75 degrees ambient I am seeing 55 psi low side 205 high. Live data shows 230 psi and says system is working normal. Low side pipe is cool-cold not cold-cold if you know what I mean and there is cool air blowing in the cabin but not enough to really make it cold in there. outlet air was in the 60-65 range.


here is another set of photos...shows pretty much the same as above.





It is heating up a bit outside so I will go and see if the system has the high pressure failure again....

 

it is still working as described above and pressures remain around reported above. Ambient temp is still less than 80.
I shut off AC and left the vehicle running and pressures equalized faster...closer to 8-10 min. maybe this is because of the fans running over the condenser...

 

1. Which engine?
2. Manual or automatic climate control?
3. Add evaporator temp sensor to your list of PIDs. Does it correlate closely with outlet air temperature?

 

3.5 liter engine
automatic climate control
vin= 1FAHP2F85JG130264

I will have to check that PID later….vehicle in use. I had looked for something like that but I didn’t see it on the list. Maybe I didn’t look close enough. If you happen to know the exact name to look for in forscan let me know

 

Currently driving the vehicle 65 mph on highway. Temperature probe out window shows ambient air at 71°. Max AC is on temperature probe in vent shows 61.4°


*update
driving home, 65 mph on the highway. 81° temperature probe it out the window, Max AC on, temperature probe in vent shows 62°

 

I cannot find this evaporator temp sensor as an available PID in ForScan. Please advise

 

You have to access the HVAC module's PIDs. That sensor's data isn't available through the PCM.

I was doing it with Forscan Lite (paid Android version) on my phone a few weeks ago but haven't dragged my laptop out to the car yet so I haven't played with it in the Windows environment. On the phone app, I had to explicitly tell it to look at the HVAC module, available individually or under "ALL", instead of the default PCM setting.

 

ok Yes I was able to access via windows as you described once I realized that you could select different modules under live data...LOL operator error for sure! thanks!
OK vent temp was about 62 and the evap was 36...also please note errors...
now when I put a paper towel over the outside cowl bottom of windshield it sucks tight, then I select recirc and it comes loose, so it does appear to be opening and closing properly, but clearly there is an error...

 

Where should I go from here?