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Discussion Starter #1
Okay, so i have a 98´durango 4*4 5.9 with dual ac.
Yesterday i did a top up with r134a, it still had about 2 bar/ 25 psi in it
but since it was fairly warm and the bottle held a nice 6 bar im rather convinced that i only had
vaporized 134 in there so it was basically empty.
I started filling and the compressor kicked in but i ended up with high suction pressure rather quickly.
- the compressor shut down and didnt want to kick in, it came back after ten minutes....
it seems like adding more refridgerant makes the compressor stop...weird, i do not have high pressure on the hp side. (switch cloosed)
- i have only got about half charge by wheight.
- Its only the rear ac unit that blows cold. ( but it bows really cold )
- both high and low pressure switches are closed with ac off.
- it cycles at 10s on/ 6s off.
What else except the pressure switches/ climate controls controls the compressor?
I also suspect that the front ac expansion valve is broken, thus no cooling at front or can this behaviour be
because of low charge?
- should i just dump the appropiate amount in there and se whats happen?
- How much overcharge can it stand?
It has never been empty or opened so i shouldnt have any air or moisture in it.
By the way refridgerant arent all that easy to come by in sweden so im hesitant to
just waste tha gas.
 

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The front and rear A/C systems are together in a parallel refrigerant path, so if the rear system is blowing cold, but the front system is not, then I would also suspect a front expansion valve problem.
 

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Discussion Starter #3
Is there anything else except the pressure switches and climate control that controls the compressor?
The expansion valve is cheap but is it mounted on the firewall and how hard is it to change?
 

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There may be an evaporator fin temperature probe (cycling switch) pushed into the evaporator to prevent freezing. It may be accessible behind the glovebox? Use care not to pull on the wires or the probe tip. It is fragile. pl807770.gif
The system refrigerant would have to be reclaimed to change the expansion valve and its gaskets/o-rings, drawn into a vacuum and recharged with the proper amount of R-134a. I believe that it is held to the evaporator flange by torx or allen screws.
 

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Discussion Starter #5
Havent had much time to work on it being on the swedish championships for icelandichorses..
but i noticed one thing that makes it look like low level of refridgerant may be able to make just
one of the coolers work.
-it changed places, the front started working slightly and the rear lost most of it cooling..
Since its just half charged, enough to start the compressor i think i should go ahead and charge it completly.
Whats the pressures for the low side switch? ( mine cycles between 2- 4 bar´s or approx 25-50 psi)
 

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If it did lose a charge, there is a refrigerant leak and you will likely lose it again.
Check for leaks while there is still some pressure in the system, then reclaim what you have in the system and fix the leak.
Draw the system down into vacuum and see if it holds vacuum, then recharge with the amount stated on the underhood A/C label.
A partial charge may cause unstable front/rear cooldown.
 

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Discussion Starter #7
it was five years since i filled it and it holds pressure ok now so
i dont think i will find any leaks.
It doesent sweat oil anywere either
 
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