I have an 06 2500 4x4 with 56k miles. my a/c compressor is short cycling. have checked refrig. pressure, installed new high/low pressure switch, new a/c compressor and a/c climate control unit in the dash, and the compressor continues to kick on and off irratically when running above idle. low side pressure 35psi high side 250psi fan clutch seems to be engaging properly. it does blow cold air when the compressor is engaged but it will not stay engaged.. any ideas? i am at a loss

 

Sounds like it's LOW on freon.

 

whats your outside temp when checking your charge?

By chart, at 80F your vent temps should be around 45F with a 25-35 Low side and 200-300 high side.

The powertrain control module (PCM) cycles the A/C compressor clutch off and on as necessary to protect the A/C system from evaporator freezing and optimize A/C system performance.

 

i live in southern oklahoma so i guess the outside temp is currently around 98 to 105 degrees. i was told by some people that the temp. sensor in the evaporator may have went haywire... know anything about that? i also had the computers flashed and that didnt fix it either

 

Unless you've replaced your refrigerant, you are low. For R-134a (what you've most likely got) at 100 degrees F, your low-side should read 50-55, and your high-side read 315-325. Pressure readings are based on refrigerant type, not vehicle/compressor/etc. The first I would do with your readings is get a 4oz. can with NO OIL added (your factory lines should still have the correct amount). Get that into your system and it should begin to function properly.

 

Here's the fill specs. I dont feel comfortable posting the pressure charts (copy write) . Does anyone have one thats not protected against reproduction?
CAUTION: A small amount of refrigerant oil is removed from the A/C system each time the refrigerant system is recovered and evacuated. Before charging the A/C system, you MUST replenish any oil lost during the recovery process.



Evacuate the refrigerant system.
A manifold gauge set and an R-134a refrigerant recovery/recycling/charging station that meets SAE standard J2210 should be connected to the refrigerant system.
Measure the proper amount of refrigerant and heat it to 52°C (125°F) with the charging station. See the operating instructions supplied by the equipment manufacturer for proper use of this equipment.
Open both the suction and discharge valves, then open the charge valve to allow the heated refrigerant to flow into the system.
When the transfer of refrigerant has stopped, close both the suction and discharge valves.
If all of the refrigerant charge did not transfer from the dispensing device, open all of the windows in the vehicle and set the heating-A/C system controls so that the A/C compressor is engaged and the blower motor is operating at its lowest speed setting. Run the engine at a steady high idle (about 1400 rpm ). If the A/C compressor does not engage, test the compressor clutch control circuit and repair as required.
Open the low-side valve to allow the remaining refrigerant to transfer to the refrigerant system. WARNING: TAKE CARE NOT TO OPEN THE DISCHARGE (HIGH PRESSURE) VALVE AT THIS TIME. FAILURE TO FOLLOW THIS WARNING COULD RESULT IN POSSIBLE PERSONAL INJURY OR DEATH.
Disconnect the charging station and manifold gauge set from the refrigerant system service ports.
Reinstall the caps onto the refrigerant system service ports.

 

Darn, did you really replace all those components? It would be very unusual even to have one of those fail on an '06, even if you dropped a half-mil miles on it.

I tried to attach the chart from my gauge set. Somehow the forum recognized that I'd attached it before (even when I changed the name), so I have to link to it instead:

https://www.dieseltruckresource.com/...t244095p2.html

The chart is posted about half-way down the page.

Also, I re-read my earlier post. I assume you added the correct amount of oil when you had the system recharged. If you did not, let us know. In the recharging of the system, I would recommend using an actual oil container rather than coolant "with oil in it", that way you can more accurately determine the amount of oil you're adding.

Also, as far as legality of posting a temp/pressure chart, that's just the characteristics of the refrigerant. They really shouldn't be copywrited.

 

as far as i know it has been re-charged after the new compressor was installed, could there be some problem because they may have re-cycled the refrigerant?

 

I must be bored today. If you changed out all those parts yourself you should have evacuated the system and recharged after your final part was replaced. If you did not evacuate the system, you need to. Any moisture in the system will have a negative effect on the compressibility of your refrigerant. I think the general rule is it had to hold a steady vacuum for 15min. The vacuum will cause moisture and residue oil to evaporate and clear out. Then you can proceed to refill as necessary.

 

Yea, It would be really off to replace really anything in the AC system at this point. Failure rates are really low for the AC componets. My concern in posting the chart come from the Chrysler corp. trademark and copywrite. Last thing I need is a lawsuit from copying and pasting lol

 

my mechanic also said the compressor was dis-engaging once the high side got to 250psi

 

It would be disengaging to protect the compressor from low refrigerant. You can add some more yourself. Get the can (NO OIL ADDED) and connect to your low side. Hold it upside down and gently swirl (maybe an old wives tale - the swirling that is). It will only draw from the can when the compressor is kicked on so it may take a little while (5 min). Check your pressures after one 4oz can and see where they stand.

 

i sure appreciate the help

 

No problem. Let us know what worked when you get it fixed. For your sake I'm hoping its just low on refreigerant.

 

If the R134A is low, When you start the filling process the compressor will start running longer and longer. Also, When the compressors off you'll see a higher reading so dont panic!

Here's the information regarding the Sensor. I've seen this 2 or 3 times.
Theory of Operation
The Cooldown Test checks A/C system performance based on Evaporator Temperature Sensor input. The main criteria is to lower evaporator temperature 11.11°C (20°F) within one minute . Before starting the test, the evaporator temperature must be above 13°C (55°F) and the front blower speed must be set to high speed. When the test is running, A/C Select and A/C Request will be on and the A/C status indicator will flash. When the test is complete, the scan tool will display one or more test status messages to indicate the outcome of the Cooldown Test. A Successful Cooldown - Test Passed status message indicates that the main test criteria was met. A DTC Set During Routine - Test Not Passed status message indicates that the A/C system is unable to lower the evaporator temperature 11.11°C (20°F) within one minute . A Conditions Too Cold - Test Not Run status message indicates that the evaporator temperature was below 13°C (55°F) when starting the Cooldown Test. A Blowers Not On High - Test Not Run status message indicates that either the front blower speed was not set to high speed prior to starting the Cooldown Test or the front blower speed was changed from high speed to another setting after starting the Cooldown test. A Refrigerant Temperature Sensor Error status message indicates that a fault occurred with the Evaporator Temperature Sensor/sensor circuits. A No Results Stored/Test Not Complete status message indicates that the power was cycled while the test was running.