2nd Gen Non-Engine/Transmission 2001 Air conditioning question

[Gordon Maney]

I did a lot of A/C work in the mid-70's, so as you can see, I have been out of it for a while. A friend has gauges and a vacuum pump, having done some basic charging and repairs. We are going to charge my truck's system.

I gather there are no sight glasses on these. I find a capacity in the manual. Do you use system pressures to know when it is full? If so, is that chart pretty accurate, or do you deviate from it in some way?

Is there a dryer that can or should be replaced? I find no mention of it in the manual.

Regarding oil, this is not a system that has leaked, so do I assume I have enough oil, or should some be added? I do know that years ago you could buy pound cans that had some oil in each can. The idea was it made up for any minor losses.

Thoughts?

This is on a 2001 24V Cummins powered Ram 2500 4X4.

 

[B.G. Smith]

Haven't done that much repair work on 134 systems but I find it very difficult to charge by pressure readings, best is to start with empty system and put in required amount, 99 FSM says 28 oz's . The system capacity is sometimes on a sticker on the core support under hood. The dryer is a combo unit of receiver/dryer and is located near the firewall on passenger side, should be changed if system has been opened up or major component changed. If you just had a slow leak and system has not been recharged several time the oil should be ok. If you replace a component like receiver/dryer, condenser, compressor there usually are instructions on how much oil to add etc. bg

 

[Gordon Maney]

Haven't done that much repair work on 134 systems but I find it very difficult to charge by pressure readings, best is to start with empty system and put in required amount, 99 FSM says 28 oz's . The system capacity is sometimes on a sticker on the core support under hood. The dryer is a combo unit of receiver/dryer and is located near the firewall on passenger side, should be changed if system has been opened up or major component changed. If you just had a slow leak and system has not been recharged several time the oil should be ok. If you replace a component like receiver/dryer, condenser, compressor there usually are instructions on how much oil to add etc. bg

I don't have a charging station and will have to do this from cans, which I believe are 12 ounces now? So, determination of the exact amount will be an estimate.

Thank you for your reply!

 

[JBringhurst]

Gordon- when you recharge, you wont get the full 12 ounces out of the can. I've heard to subtract 2 ounces for what you can't get out of the manifold gauge lines and subtract 1 ounce per can.

 

[Gordon Maney]

Gordon- when you recharge, you wont get the full 12 ounces out of the can. I've heard to subtract 2 ounces for what you can't get out of the manifold gauge lines and subtract 1 ounce per can.

Thank you, that is important information.

The bulk of the work I ever did was on systems with sight glasses, and you charged until the glass ran clear. That was easy.

 

[JDKammin]

There is an orfice tube in the outlet tube of the condensor. I put a new condensor in and installed a new orfice tube. I happen to have R134A in a 30# keg and have a digital scale that I can put the right amount in the system, which happens to be 2 lbs in my 1996 system. Make sure you vacuum the system down for a few minutes and close the valves on the gauges. Watch the low pressure gauge and make sure it holds vacuum for 5-10 minutes. If it does not hold, you need to figure out where your leak is. If it holds vacuum, I would continue to vacuum the system down for 20-30 minutes, then charge the system with 134A.

 

[Gordon Maney]

There is an orfice tube in the outlet tube of the condensor. I put a new condensor in and installed a new orfice tube. I happen to have R134A in a 30# keg and have a digital scale that I can put the right amount in the system, which happens to be 2 lbs in my 1996 system. Make sure you vacuum the system down for a few minutes and close the valves on the gauges. Watch the low pressure gauge and make sure it holds vacuum for 5-10 minutes. If it does not hold, you need to figure out where your leak is. If it holds vacuum, I would continue to vacuum the system down for 20-30 minutes, then charge the system with 134A.

Are you emphasizing the orifice tube part of your comments? Meaning, are you saying you feel replacing that is critical?

 

[madmanmanick]

If you totally evacuate the system, than you should pull it down into a deep vacuum. If you can park your truck overnight the best thing you should do to make sure your system is sound is to pull the system down to as close to 30" vacuum. Then let it go overnight, closer to 24 hrs the better. It should not drop. If it drops a lot then you have a leak. When doing from vacuum to pressure make sure you put vapor back into it until the pressure gets back to 0psi or you run the risk of cracking the piping if you put liquid in. The previous post about using a 30 lb bottle and a digital scale is the best way to charge your system. Using the small 12oz bottles allows for a possibility for air getting into the system. if the air has moisture in it the refrigerant and the water will mix and become acid that will eat your seals. Also if you empty your system you may want to put in a can of oil into the system to make sure the system is properly lubricated. Hope all this helps.

 

[Joe Mc]

OK here's my shade tree method. FYI - old HVAC Tech, hopped off the bandwagon right around the time when system reclaim became the norm circa 1992ish.

What everyone is saying above is true and correct. However, my truck requires a recharge every 2-3 years. What I do is as follows: if system is low = still has pressure but not enough to allow compressor to run, you can find out by trying to release some psi - I connect hose to 12 oz can, twist valve in to puncture can top and back off a little so you can barely hear a hiss. Connect up to low side quick connect, have engine running w/AC on max, fan speed high, all registers except 1 center closed, all windows up, and a thermometer placed into the open register positioned so you can read it from outside drivers door without opening it. Start feeding gas to go into the system = open valve on line/can wide and keep hand on the can, you'll feel it get cool as the liquid boils into a gas, once the can is no longer cool you can hold it by the top of the valve and move it to and fro a few times then stop - if there's liquid left in the can you can feel it swishing around as you stop moving the can. If there's liquid left in side just shake the can to help boil off liquid. When you are confident the can is empty close valve on top of can and remove quick connect, install on another can and repeat.

Now, as you are adding cans into the system periodically feel the line leaving the condenser (by the radiator, runs behind the battery) it should get progressively hotter. The line leaving the tip of the receiver (by the turbo and the line leaves heading to the compressor) should get progressively cooler as you add refrigerant. I continue to add gas until I get about a 45 - 50 air temp on the thermometer and when the receiver is fully sweating.

If frost starts to appear on the line entering the receiver you probably have too much refrigerant in and can get a liquid floor back to the compressor = not good, liquid doesn't compress = by by to your compressor.

I know this method is considered crude, but it works and has for me with many cars and my truck over the past 9 years = 3 recharges.

If you have a leak that depletes the charge in a few months then more than likely the leak is in the evaporator (in the heat/ac box) and the dash must be removed to replace the evap coil. Not a fun job = why I keep feeding 134a to mine every 2-3 years or so.

Be cool my brother.