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What is the procedure to test a front and rear system for a stuck expasion valve?

bteddy on Wed August 04, 2010 10:17 PM User is offline

Year: 1997
Make: Plymouth
Model: Grand Voyager
Engine Size: 3.3L
Refrigerant Type: 134a
Ambient Temp: 90
Pressure Low: 45
Pressure High: 250
Country of Origin: United States

Hello,

I replaced a broken high side line. Replace the accumulator. Replaced oil. Vacuumed system for 2hrs (was opened for a couple of months). Let sit for an hour to see if the system would hold the vacuum.

Started charging system, at the 3/4 full point (36oz of 48oz) the gauges were reading the max for the system.
I ran the engine for an hour and the reading decreased to below max.
I added the last 12oz and the pressures went up to Low: 45psi (37psi max) and High: 250psi (210psi max).
I ran the engine for a couple of hours (drove around town) after and measured again, no change.

The system dual zone, front and rear, the front blows cool, not cold, intermittently and the engine overheated . I could not tell what the rear was doing, couldn't run rear without running front.

Questions:
1)What is the procedure to test for a stuck expansion valve?
2)How do you determine if it is the front or rear expansion valve that is stuck?
3)How do you unstick an expansion valve?
4)My low side connection valve is near the line connection to the compressor and the high side is in-between the expansion
valve and the accumulator, what would I disconnect, and where would I hookup to back flush the system if it is contaminated?
5)There is not a sight glass on the system, is there a way to test for air/moisture in the system?

Thank you for any help you can provide.

mk378 on Thu August 05, 2010 1:00 AM User is offline

Overheating the engine may be because of a radiator / condenser airflow problem. Do all the fans work?

bteddy on Thu August 05, 2010 1:16 PM User is offline

Both were cleaned and the fans are working.

CFSpit on Thu August 05, 2010 5:37 PM User is offline

What temp of air is coming out of your vents? Your high & low pressures sound pretty right on to me.
I have a 97 grand caravan with the same set-up. Did you change the drier? Are you sure that your air blend doors on your heating unit are working properly?

You could have air in the sealed system I suppose. Your system properly charged should take 48 oz of R-134 if it didn't take 48 and it has the pressures it does...maybe there is air in the system? I'm no expert but I would think that if you had a lot of moisture or debris in the system your pressures would be off..too high or too low on one side or another.

My system did have some type of blockage in it recently and the high pressure release on top of the compressor opened and shot out oil & R-134 (shoots it right at the coolant overflow container). The funny thing was that my High pressure reading was low. Which means that the restriction had to be between the compressor and the drier either one of the condensers or the drier, I ended up replacing both condensers and the drier along with the evaporator which had leaks..had been leaking for years. I'm not sure but the high pressure release may be set for over 400 psi.! so the compressor was doing it's thing it just couldn't get the right pressure to the expansion valve.

Spit

bteddy on Thu August 05, 2010 9:37 PM User is offline

Questions:

1)What is the procedure to test for a stuck expansion valve?

2)How do you determine if it is the front or rear expansion valve that is stuck?

3)How do you unstick an expansion valve?

4)My low side connection valve is near the line connection to the compressor and the high side is in-between the expansion
valve and the accumulator, what would I disconnect, and where would I hookup to back flush the system if it is contaminated?

5)There is not a sight glass on the system, is there a way to test for air/moisture in the system?

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