[WK2] AC Compressor disengaged when HOT - JeepForum.com
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post #1 of 10 Old 06-30-2020, 10:43 PM Thread Starter
bts_wk2
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[WK2] AC Compressor disengaged when HOT

Hi all,
I got a problem on my WK2, AC is working well when start and after couple of 30 minutes, it's freezing cold and run well, until coolant temp reach 95C (203F), when the coolant getting higher to 96-98C (208F), the AC compressor clutch disengaged and AC not cold anymore, need to wait couple sometimes until engine cooler and clutch start engage again. No overheat indication shown, coolant looks normal and radiator fan works good, its start and stop when needed. Just wondering, who trigger signal to AC clutch and why disengage too soon.

I brought to JEEP Authorized dealer for checking, and they asked to replace the whole radiator fan and whole TIPM (Totally Integrated Power Module) which cost me $2800, which I refuse !!
I am wondering if it is simply fan relay control or other clutch relay replacement. I am thinking to put extra cooling fan on the front to force the engine to cool down.
It's surprising me JEEP can't pinpoint the problem or troubleshoot this issue

Need your advise

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post #2 of 10 Old 07-01-2020, 07:20 AM
ColdCase
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You didn't mention engine size and if you have SD or HD cooling. SD cooling has a fan relay in the TIPM. The HD fan it is driven by a PWM signal from the TIPM circuitry, no relay.

It sounds like the dealer thinks there is not enough air being drawn through the condenser because of a fan failure. The AC pressure builds up enough for the PCM to shut the compressor down. Is the cooling fan spinning up? What were the error codes? Perhaps a problem in the fan burned out the TIPM. Dunno, just guessing. Adding another fan may help.

A/C compressor clutch engagement is controlled by the Powertrain Control Module (PCM), the control drivers are in the TIPM. There are a couple pressure sensors that tell the PCM the AC status and if out of spec, it will disengage the AC clutch. The PCM will request disengagement of the A/C clutch when high side pressure rises above 3219 kPa (476 psi) and re-engage the clutch when high side pressure drops below 2937 kPa (426 psi). The PCM will also disengage the A/C clutch if the high side pressure drops below 110 kPa (16 psi) and will re-engage the clutch when the high side pressure rises above 220 kPa (32 psi). When the refrigerant pressure rises above 1655 kPa (240 psi), the PCM will actuate the cooling fan.
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post #3 of 10 Old 07-01-2020, 07:42 AM
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Clean out the condenser? We have a ton of cottonwood trees around and it snows that crap sometime.

Over charged system? May need to check the pressures and drain some R out.
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post #4 of 10 Old 07-01-2020, 11:07 PM Thread Starter
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bts_wk2

Thanks a lot mate,
engine is 5.7 HEMI, Limited trim, i am not sure if the fan is SD or HD, no idea. Fan is working fine, in low and high speed, no indication of overheat, and no error code detected by OBDII scanner.
Do you think pressure sensor need replacement. I tend to disagree with dealer, they just simply want to replace whole TIPM and cooling fan. I will try to add extra fan instead

Quote:
Originally Posted by ColdCase View Post
You didn't mention engine size and if you have SD or HD cooling. SD cooling has a fan relay in the TIPM. The HD fan it is driven by a PWM signal from the TIPM circuitry, no relay.

It sounds like the dealer thinks there is not enough air being drawn through the condenser because of a fan failure. The AC pressure builds up enough for the PCM to shut the compressor down. Is the cooling fan spinning up? What were the error codes? Perhaps a problem in the fan burned out the TIPM. Dunno, just guessing. Adding another fan may help.

A/C compressor clutch engagement is controlled by the Powertrain Control Module (PCM), the control drivers are in the TIPM. There are a couple pressure sensors that tell the PCM the AC status and if out of spec, it will disengage the AC clutch. The PCM will request disengagement of the A/C clutch when high side pressure rises above 3219 kPa (476 psi) and re-engage the clutch when high side pressure drops below 2937 kPa (426 psi). The PCM will also disengage the A/C clutch if the high side pressure drops below 110 kPa (16 psi) and will re-engage the clutch when the high side pressure rises above 220 kPa (32 psi). When the refrigerant pressure rises above 1655 kPa (240 psi), the PCM will actuate the cooling fan.
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post #5 of 10 Old 07-01-2020, 11:18 PM
ColdCase
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If you know your way around AC, then you could put a gage set on it and see what the pressures look like. With a scanner you could look at the pressure the sender is indicating and compare to the gauge set. Otherwise have a competent AC shop look at it and make the measurements and offer suggestions.

Check to see if the condenser fins (in front of the radiator) are clogged.

The WK2s have a tendency tp freeze up evaporators, but that doesn't appear to be your issue.
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post #6 of 10 Old 07-01-2020, 11:36 PM Thread Starter
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Thumbs up

appreciate your prompt response =)
condensor is brand new, 2 months ago. will do to check the refrigerant pressure.
the control system of compressor activation on PCM looks complicated, that's why dealer want to simply replace that.
do you have any idea where are the refrigerant pressure sensor located ?

Quote:
Originally Posted by ColdCase View Post
If you know your way around AC, then you could put a gage set on it and see what the pressures look like. With a scanner you could look at the pressure the sender is indicating and compare to the gauge set. Otherwise have a competent AC shop look at it and make the measurements and offer suggestions.

Check to see if the condenser fins (in front of the radiator) are clogged.

The WK2s have a tendency tp freeze up evaporators, but that doesn't appear to be your issue.
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post #7 of 10 Old 07-02-2020, 06:32 AM
ColdCase
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Has this problem been going on for a long time?

Why don't you think its a problem in the expansion valve, or was that replaced too?

The A/C pressure transducer monitors the pressures in the high side of the A/C refrigerant system through its connection to a fitting on the A/C discharge line and its internal resistance changes in response to the pressures it monitors. The Totally Intergrated Power Module (TIPM) provides a five Volt reference signal and a sensor ground to the A/C pressure transducer, then monitors the output voltage of the transducer on a sensor return circuit to determine refrigerant pressure the TIPM busses the reads to PCM.

You may also want to check the condition of the harness and connections, these can corode and intermittently cause false readings. The TIPM is on the list of possible causes, but at the end after the circuits are teated and pressure transducer. There may be some TIPM DTCs set, but you need a scanner that can read body module codes to know if their there. Your typical OBD scanner will find nothing even if an error is set.

The pressure transducer #3 in the diagram below. It is not necessary to discharge refrigerant to replace it, just screws onto the fitting.
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Screen Shot 2020-07-02 at 8.28.41 AM.jpg  
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post #8 of 10 Old 07-02-2020, 07:18 AM Thread Starter
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ColdCase,

your explanation is crystal clear.....5 stars !!
it's make sense. I don't think expansion valve nor the compressor are the problem, since when the clutch is engaged AC is very cool and looks good. the only problem happen when clutch disengaged unexpectedly on high coolant temp.
I have OBDII scanner, and multiple times scanned, NO DTC error found.
So, I will try to replace : pressure tranducer (part #68308727AA), cooling fan relay (just in case weak). It's pretty much cheaper than following dealer recommendation to replace TIPM and whole cooling fan unit for $3000 !!

THANKSSS

Quote:
Originally Posted by ColdCase View Post
Has this problem been going on for a long time?

Why don't you think its a problem in the expansion valve, or was that replaced too?

The A/C pressure transducer monitors the pressures in the high side of the A/C refrigerant system through its connection to a fitting on the A/C discharge line and its internal resistance changes in response to the pressures it monitors. The Totally Intergrated Power Module (TIPM) provides a five Volt reference signal and a sensor ground to the A/C pressure transducer, then monitors the output voltage of the transducer on a sensor return circuit to determine refrigerant pressure the TIPM busses the reads to PCM.

You may also want to check the condition of the harness and connections, these can corode and intermittently cause false readings. The TIPM is on the list of possible causes, by at the end after the circuits are teated and pressure transducer. There may be some TIPM DTCs set, but you need a scanner that can read body module codes to know if their there.

The pressure transducer #3 in the diagram below. It is not necessary to discharge refrigerant to replace it, just screws onto the fitting.
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post #9 of 10 Old 07-02-2020, 07:24 AM
ColdCase
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I think all V8s have HD cooling which has a variable speed fan. You may look hard but not find a functioning fan relay because they don't use one. To test them you need a scanner that can set fan speed and observe the fan spinning at the expected rate.

I was born with nuttin' and I still have most of it
Current: 2011 Grand Cherokee Overland V8, 2009 Liberty Rocky Mt V6
Previous: 2000 Grand Cherokee Laredo I6, 1979 CJ7 I6 Quadratrac
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post #10 of 10 Old Yesterday, 10:21 PM Thread Starter
bts_wk2
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[UPDATE]
extra cooling fan installed in front of condenser, just behind front grill. No Hot air anymore so far, coolant temp is now stable at 95C and no unexpected clutch disengage. I am expecting AC pressure switch, which i bought online from Mopar. I hope all problem will be solved
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