Engine Size: I6D
Refrigerant Type: R134
Ambient Temp: 95
Pressure Low: 25
Pressure High: 275
Country of Origin: United States
For those of you that know, I have replaced the compressor, liquid line, condenser and drier all at the same time a few months ago. I pumped down the system with a 5fcm robinair pump and installed the proper amount of freon. The a/c worked for a few months until recently it got hotter and hotter.
My compressor was cycling on and off so I hooked up my gauges and added about 1/2 can of r134 to the system. The compressor stopped cycling so rapidly which was good but the a/c still blow hot. The gauges read 25/275 in 95 degree weather.
The condenser is getting hot. The liquid line that goes from the condenser to the firewall is hot towards the front of the truck and is ice cold (with condensation on the line) towards the firewall side. The other line coming from the firewall into the drier is normal (warm temp) the same as the actual drier itself.
What is happening? Is the box inside the truck plugged? Is this the symptoms of low refrigerant? What do I need to do to trouble shoot this further
Heres a picture of whats going on. Im not that great of a graphics person....
When the compressor kicks in how long does it take to pull the pressure down? If you measure the time period from when the compressor kicks in to when it kicks in again, how long is that? And in that time cycle how many seconds is the compressor on for?
I would expect the bottom of the accumulator-drier to feel the same temperature as the blue line downstream of the orifice tube. Because it isn't, either the orifice tube is partially plugged or the system is low on refrigerant. In either case not enough liquid is fed to the evaporator and this is causing the refrigerant to quickly boil off and become a hot vapor, which is why that compressor suction line is warm and not cold.
Do you know if you have any leaks that would have caused you to loose refrigerant?
One check you can do is measure the liquid line temperature coming out of the condenser and compare that to the condenser's saturation temperature (the high side temperature read directly off the R134a gauge). The liquid line temp should be lower than the saturation temperature. Under heavy evaporator heat load if the system is flowing a lot of refrigerant (orifice tube not plugged) and if the refrigerant isn't backed up in the condenser at all then it may not be fully condensing in there. As a result the liquid leaving the condenser will be at the saturation temperature shown on the gauge. That means two things. 1) you likely still have vapor exiting the condenser along with the liquid and this will degrade performance. 2) #1 is happening because the system is low on refrigerant.
You are losing refrigerant- still needs more to work right-- sadlly, I highly suspect a leaky evaporator- have seen quite a few on Dodges- a good sniffer and some dye will confirm- look for dye at or around foam insulation at evap drain tube once you know you have dye in the system...
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......
Edited: Mon July 14, 2008 at 4:28 PM by GM Tech
I drained the new compressor free of oil...measured it and found it was a bit low so I added about 1/2 an ounce to make it 6.25 oz which is what the system calls for.
Because I put all the oil in the compressor when it was new, would that have plugged the liquid line?
Sure you can rev that diesel up to 1,500 rpm, AC on blower at max, a door open to give the correct pressures and noting those pressures at the ambient and RH conditions will provide a good reference for two weeks down the road or whatever to tell you if you have a leak.
Hecat, is that based on the theory that if a little medication or fertilizer is good, a lot more is much better?
A little is good, a little more can be better, and too much can be bad.
Ok I found that my evap core was plugged. What a pain that was to remove and reinstall
My question now is...Do I need to add any oil to the system?
Of course I had to disconnect the lines and I dont have a recovery system so I will be adding 2.5 cans tomorrow
How can I measure how much I need to put back in, if any?
can anyone tell me how I can tell how much oil I am suppose to add after replacing the evap core?
I cannot tell you how much, but a guess would be about 2 or 3 oz. Wait to see if you get more guesses that may help you decide.
I have to ask, what clogged the evap after it was flushed a few moths ago?
Its probably like you said before...evap core leaked refrigerant (it was very old) causing the oil to boil and plug the evap core. What else could it have been? The truck does have 200k on it.
I will check for leaks with UV dye when I go to fill it up. Plus the refrigerant I am using has leak seal that may help out in the future.
Edited: Fri July 18, 2008 at 3:22 PM by EverydayDiesel
Sorry, leak seal answers my question. DO NOT use it.
Never ever use leak seal. Here is another example of how it clogs stuff up on the inside. Clogging an evaporator is a pretty mean feat. Was your experience also that the leak seal was ineffective at stopping the leak to the outside?
The original Dodge evaporators were of low quality and leaked. A replacement from a reputable source will be different and will last the life of the truck.
Ok I will take the leak seal back and get the regular stuff.
I did not use the leak seal before but I bought it this time thinking it would be better.
Its a good thing I did not open it. Thanks for the advice.
Although the refrigerant is boiling in the evap, it is not generating the kind of heat that would cook the oil and clog the evap. It boils at a minus 15-20 degrees to carry away the heat load applied from the recirculating cabin air. If you have not used refrigerant with leak sealer before, then I am very happy we could warn you and you will exchange. However, this opens up the question again as to what has clogged the evap? Maybe if you get a chance, you could cut it open and post what it looks like.
I have exchanged the r134 for 3 cans of johnsens
I will cut it open and take pictures. I added 6.25 oz of pag150 which is what the system called for but I put all the oil inside the compressor.
The condenser, drier, compressor, and liquid line was new. I flushed the evapcore out with a/c cleaning chemicals. It may have been plugged before not plugged 100%.
I did buy the truck used and it has about 200k on it right now so who knows what the previous owner did to the a/c system.
Ill get some pictures of the core cut open.
Thanks everyone for the help...especially you HECAT
Edited: Sat July 19, 2008 at 5:25 PM by EverydayDiesel
Is "Everyday Diesel's" diagram correct? On my oem setup--Ford F350--the receiver/dryer "in" is connected to the liquid line coming out of the condenser (lower port), then from receiver/dryer to the evaporator. Compressor connections are: from evaporator outlet to suction side of the compressor, then high pressure gas outlet hose connects to the inlet (top) port on the condenser. No lines from the compressor are attached to the receiver.
Edited: Sat July 19, 2008 at 7:30 PM by vettman
All the proper terminologies of receiver, dryer, filter, accumulator, etc.; get mixed up sometimes.
Filter device in high side line between cond and evap - TXV system (like your Ford).
Filter device in suction line after evap - OT system (like his Dodge).
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