I have taken my 2000 Dodge Grand Caravan to a local shop to have the AC charged (after I installed the new evaporator)

It leaves the shop (all on cool days - around 70) and the mechanic thinks it is fixed. (3 times now)

The first hot day (80+) the AC just won't cool.

The last time I took it back, they said the gases were just fine and nothing was wrong. (it was nice and cool) ..and it seemed to be working

The next day I drove it on the highway and ABSOLUTLEY NO cool air coming out!

- I checked and the gasses we showing red (on my autozone AC fill gauge)
- The dampers were working (heat side was scorching)
- The AC clutch seemed to be engaged

- I did hear hissing under the dash - only when the AC is on (but the system has lost no gas) - so is this the valve regulating pressure?

QUESTIONS:

- If the gasses are in the system, the pump seems to be working, the duct system is working....the what could be keeping the AC from being cool?

- How do I know if the H valve (on the evaporator connection) is working or stuck?

- Are there pressure switches that I can test?

- How do I diagnose the AV system ?

- How do I make sure the system has the proper gas levels?

I appreciate any and all help.

 

more details....

Saturday, the ac just blows hot air. I check it with my gauge and it is in the red with too much pressure.

Sunday I check it again (much cooler day and set all night) and the gauage shows pressure much lower (low enough to add a bit)

I add a can(with dye trace)....at first it doesn't take, so I rev the engine a bit and shake the can, it eventually goes in and....I now have "colder air" coming out - not freezing, but colder air.

It is actually cold enough to enjoy as air conditioning.

QUESTION: could the addition of gasses actually have opened a sticky H valve?

Is this why, when my ac is hot, I take it to the shop, they add some gas and tell me there is nothing wrong? ...because the added gas pops open the H valve?

Is this why I hear hissing from time to time under the dash when the AC is running?

I appreciate any help given.

-Shawn

 

It may be overcharged. If the pressure is in the red zone, the high pressure switch will cut everything off.

 

How much freon should a 2000 grand caravan have?

 

Mr. M, Did you happen to replace the thermal expansion valve (TXV) when you did the evap replacement? Not an expert, but my understanding is the valve senses the gas temp of the evap outlet and open or closes the valve to regulate the amount of refrig going into the evap in order to to attain superheat. So if the valve is bad, the a/c may work intermittently or just fail to keep the correct pressure in the evap.

A TXV is different from an orifice regulator which just keeps the pressure in the evap at a constant pressure.

Don't know if this is your problem. But, check both the high and low side pressures. I believe you should see around 200 on the high and about 40 on the low when the system is running.

 

What does the valve look like? Is it the one I show here:

https://dodgeforum.com/forum/dodge-c...my-o-ring.html

 

sorry BUT questions before ideas:
1)front and rear air?
2)was the system flushed
3) ever use a "sealer/stop leak"
4) IMPORTANT - did you or the shop evacuate the system? (pull a vacuum)??????????
5) if applicable have you run a diagnostic in the Digital heater control panel
6) is the CEL on?

step 1for A/C you NEED the readings BOTH hi and low...


"- How do I make sure the system has the proper gas levels?"
The only way to accurately measure charge is to remove and weigh in the correct amount... BUT the readings HIGH and LOW can guide us...

 

answers to questions:
1)front and rear air? - yes
2)was the system flushed - (evacuated, yes - flushed- not that I know of)
3) ever use a "sealer/stop leak" - yes
4) IMPORTANT - did you or the shop evacuate the system?
(pull a vacuum)?????????? - yes (they said it was ok - but I have since found a leak with the expansion valve connection o-rings) - so I don't trust the shop
5) if applicable have you run a diagnostic in the Digital heater control panel - not sure what that is
6) is the CEL on? (what is CEL)?

 

#5 the heater control panel can run a self diagnostic ck*....while I look up button sequence for your model and year Hopefully someone will post it

#6 CEL = Check Engine Light - AKA...... MIL, SES,


*MOST climate controls panels.

 

I think this is procedure..... if you have a different control head this wont make sense then ck owners manuap

CALIBRATION/DIAGNOSTICS TEST ENTRY
TO INITIATE TESTS:
Set Blower motor ON HIGH
Set Mode position to Panel
Set Temperature to Cold (Both slide pots if equipped)
Depress WASH and REAR WIPER button simultaneously for 5 Seconds (Until all LED's light)
RESULTS:
All LED's will turn on for 5 Seconds
Calibration Test is running when REAR WIPER and INTERMITTENT are alternately flashing. Cooldown test is running if A/C and RECIRC are alternately flashing.
Acceptable results is REAR WIPER LED is the only LED flashing. Push Rear Wiper to exit.
After all tests have passed, Calibration Diagnostics and Cooldown can be run separately.
COOLDOWN TEST ENTRY
TO INITIATE TESTS:
Set Blower motor ON HIGH
Set Mode position to Panel
Set Temperature to Cold (Both slide pots if equipped)
Depress WASH and A/C simultaneously for 5 Seconds
NOTE: If the evaporator is already cold, operate system with A/C OFF and the blower motor ON high for three minutes prior to starting test.

RESULTS:
All LED's will turn on for 5 Seconds (Until all LED's light)
Cooldown Test is running when A/C and RECIRC. are alternately flashing. If A/C and RECIRC. are flashing simultaneously, Cooldown has failed. Make sure that the Blower motor is ON high, and temperature is ON full Cold, abort test and repeat Calibration Diagnostic and Cooldown test again.
Calibration Test is running when REAR WIPER and INTERMITTENT LED's are alternately flashing.
After all tests have passed, Cooldown test can be run separately.
Acceptable results is REAR WIPER LED is the only LED flashing. Push Rear Wiper to exit.
CALIBRATION DIAGNOSTICS AND COOLDOWN ABORT
Test can be aborted by doing one of the following:

Depressing Rear Window Defogger, RECIRC and Rear Wiper buttons.
Cycling Ignition OFF and then ON.
Control will automatically abort after 15 minutes from the time Calibration Diagnostics and Cooldown was entered.
The HVAC control module will return to normal operation or may indicate unsuccessful Calibration Diagnostics or Cooldown test by LED's flashing simultaneously.

CALIBRATION/DIAGNOSTICS TEST ENTRY
TO INITIATE TESTS:
Set Blower motor ON HIGH
Set Mode position to Panel
Set Temperature to Cold (Both slide pots if equipped)
Depress WASH and REAR WIPER button simultaneously for 5 Seconds (Until all LED's light)
RESULTS:
All LED's will turn on for 5 Seconds
Calibration Test is running when REAR WIPER and INTERMITTENT are alternately flashing. Cooldown test is running if A/C and RECIRC are alternately flashing.
Acceptable results is REAR WIPER LED is the only LED flashing. Push Rear Wiper to exit.
After all tests have passed, Calibration Diagnostics and Cooldown can be run separately.
COOLDOWN TEST ENTRY
TO INITIATE TESTS:
Set Blower motor ON HIGH
Set Mode position to Panel
Set Temperature to Cold (Both slide pots if equipped)
Depress WASH and A/C simultaneously for 5 Seconds
NOTE: If the evaporator is already cold, operate system with A/C OFF and the blower motor ON high for three minutes prior to starting test.

RESULTS:
All LED's will turn on for 5 Seconds (Until all LED's light)
Cooldown Test is running when A/C and RECIRC. are alternately flashing. If A/C and RECIRC. are flashing simultaneously, Cooldown has failed. Make sure that the Blower motor is ON high, and temperature is ON full Cold, abort test and repeat Calibration Diagnostic and Cooldown test again.
Calibration Test is running when REAR WIPER and INTERMITTENT LED's are alternately flashing.
After all tests have passed, Cooldown test can be run separately.
Acceptable results is REAR WIPER LED is the only LED flashing. Push Rear Wiper to exit.
CALIBRATION DIAGNOSTICS AND COOLDOWN ABORT
Test can be aborted by doing one of the following:

Depressing Rear Window Defogger, RECIRC and Rear Wiper buttons.
Cycling Ignition OFF and then ON.
Control will automatically abort after 15 minutes from the time Calibration Diagnostics and Cooldown was entered.
The HVAC control module will return to normal operation or may indicate unsuccessful Calibration Diagnostics or Cooldown test by LED's flashing simultaneously.