A/C intermittently blows cold/warm air?

2013 DODGE GRAND CARAVAN
119,000 MILES • 3.6L • AUTOMATIC
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JOEPETERSON56
  • MEMBER
  • 7 POSTS
System began blowing warm to hot air. Checked pressures & they were all over the place, & high on both Hi & Lo lines. Then somebody who has ridden in the back told me that the back system had been blowing warm air for quite some time. Used 2 diff scanners to run HVAC System Checks, ran all the tests in HVAC tests, all doors, actuators fans work fine, but it could not pass cool down test. I changed the Rear evap & H-block exp valve, lines from front to rear due to damage caused by typical Dodge corrosion where lines connect to rear system & H-block evap valve due to the placement & lack of protection. Also replaced condenser, compressor, receiver/drier, pressure switch, Front H-block exp valve. Completely vacuumed system for over an hour after evac, then system held vacuum for 45 minutes. Recharged with proper amount of 134A. Pressure readings still seem to be somewhat high on Lo side, and slightly high on Hi side. It seems to still be a bit erratic, but seems to work fairly consistent at higher RPMs, and at idle much more erratic blowing warmer air. Could it possibly be a bad New H-block valve, or a blockage in front Evap necessitating a complete Dash/Console removal & Front Evaporator Removal & Replacement?
Aug 21, 2026 at 2:13 PM

What to check next

Diagnostic guidance. Suggested checks and possible repairs are separate from the owner's reported results.

Before authorizing dashboard removal, record both refrigerant pressures, ambient temperature, vent temperature and operating conditions when cooling fails. Have commanded and actual condenser-fan operation checked; seeing the fan turn does not establish that all required speeds work. Review the refrigerant charge by weight and the oil accounting for all replaced components. Then investigate a valve or restriction only if measured pressures and temperatures support it. A qualified A/C technician should perform recovery or charge corrections. The idle-related pattern gives a useful starting point in airflow and system setup. It does not yet establish that the front evaporator needs replacement.

Guidance references and applicability

HELLA: Air-conditioning diagnosis https://www.hella.com/techworld/ae/technical/car-air-conditioning/car-air-conditioning/ General pressure-pattern and condenser-airflow diagnostic reference. Its examples do not establish the correct charge or pressure readings for this vehicle. DENSO: A/C compressor installation guide https://assets.denso-am.eu/production/attachments/AC-Compressor-Installation-Manual-multilingual.pdf Supports application-specific oil accounting, contamination assessment and proper refrigerant recovery. Follow the installed compressor manufacturer's instructions; no universal oil quantity is prescribed here.

Read the replies · Discussion summary and reported outcome

AI-ASSISTED GUIDANCE · REVIEWED BY 2CARPROS
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STRAILER
  • ✓Experienced Mechanic
  • 55,540 POSTS
The first thing I need to ask is do you hear or see the radiator cooling fan running while the system is on? If not this is your problem. Also, I would use a garden hose to help blow out and clean the cooling fins in the condenser and radiator, make sure there is no plastic bag stuck between the two as well. In hot weather, the low side should be about 50 PSI and the high side should be about 230 PSI. please let me know what your pressures are. Here is a video that might help as well.

https://www.youtube.com/watch?v=4EqdrBVb0sY

Let me know.
Aug 22, 2026 at 8:52 AM
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JOEPETERSON56
  • MEMBER
  • 7 POSTS
Yes I do see & hear the fan running while the system is on, but it turns on and off while the system running. What I am not sure of, is whether it is running on Hi or low or both. The shroud makes it hard to see the spinning blades, but I can hear & feel it running, just not certain if it is always the same speed or not. No clogs or blockages on or between the radiator or condenser, & the condenser is brand new. As to the readings, I have taken a break from this for awhile due to the frustration & the darned heat waves we have been having here, so I will have to find & pull my last readings or take news ones as soon as I get a chance, but I do recall that both were high.
Aug 22, 2026 at 9:01 AM
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STRAILER
  • ✓Experienced Mechanic
  • 55,540 POSTS
Okay, I hear ya, also I have seen too much compressor oil cause intermittent AC operation. So with it hot outside what are the high and low side pressure reading?
Aug 23, 2026 at 9:19 AM
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Discussion summary

A/C intermittently blows cold/warm air?

The owner reported intermittent warm air after extensive front and rear A/C repairs. Cooling was less consistent at idle, and both pressure readings were described as high. The fan ran, but the owner could not confirm its speed. Actual readings and a final diagnosis were not supplied.

Reported outcome: No final diagnostic readings or successful repair were reported.

Correct charge and oil balance were reported or assumed rather than independently verified. Generic pressure figures in the replies are not used as specifications.

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AI-ASSISTED SUMMARY · REVIEWED BY 2CARPROS
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