A/c "problem" Volvo 780 cummins Isx

had the same thing happen when mine went out. take it to the dealer when the a/c comp went to lunch it blow junk into the system, a evac and recharge will not fix it, it needs to be flushed

 

Did you replace the dryer(also might be called the receiver or accumulator) when you did all this? It should be replaced any time the system is open to atmosphere, but I would think it would be especially important when you've had a compressor failure.

 

I'm a residential/commercial HVAC technician in my other life. I'd much rather work on a 20 ton commercial unit with 3 compressors than a vehicle unit. But I'll offer some thoughts.

It sounds like the compressor burned up. If that is the case it should have been flushed before the new compressor was installed. If you installed the compressor and took it in they may have assumed you did that. They should have asked, but you wouldn't want the new compressor connected while you do it.

On the limited vehicle units I have worked on, I have never had success unless the receiver/dryer was replaced. If you didn't replace it, they may have assumed you did. They should have asked. Still if you just took it to them and told them to evacuate and charge then that could be the problem.

Since the EPA took over 20 years ago the flushing options are limited. I have never heard of blowing it out. The best way, although illegal, is to flush with refrigerant. If the system was contaminated they shouldn't have been able to successfully pull a vacuum if they used a micron gauge like they should have.

If there were restrictions in the system, the second place you took it should have detected that when charging by superheat or subcooling. I'm not sure which is the proper method on that system.

One other thing that comes to mind is the compressor. What if you got the wrong compressor?

So I'll offer a couple of suggestions as to what I would do. It's not much help but, even having a HVAC Journeyman's license, I would have taken it to someone so they would have had to make it work right. I don't say this to slam you but to let you know how persnickety I think vehicle air conditioners are and I have made a good living working on residential and commercial units.

If I were going to try to fix it I would check to be sure the correct compressor is installed, flush the system (I can't suggest an illegal method), replace the receiver/dryer, evacuate with a micron gauge and charge using the method suggested for that unit.

If I took it to the shop, I would share with them everything I have posted and have an in-depth discussion with them to see if they understood and appeared to be knowledgeable.

 

At this point, I think you should take it to a professional.
You will save time, money, and frustration.

 

EXPANSION VALVE. Let me tell you a story about a brand new w900 with a ISX. 1st trip to vegas I took it to KENWORTH because it wasn't getting cold enough for me. I was told I didn't have the right knob turned on!! (BS) Back to Ohio to my local KENWORTH DEALER which I spent around $500.00 on what I can't remember. Keep in mind this is a brand new truck. In YUMA, AZ the AC goes out and I ended up in Tuson, AZ and another $800.00 to get it working. A few months later heading to LA it gives out in TULSA, OK which I find a OFF the wall AC repair shop and I had them to replace every #### thing related to the AC.... $1,400 .Turned it on and it was somewhat cold but the second I turned the bunk AC on it began to get warmer... All this time and money spent was because of a $32.00 part..(THE #### EXPANSION VALVE IN THE BUNK) I'M JUST SAYING!!

 

flood got it right. When your old compressor let go, it probably blew it's guts all through the high side of the system. You will have either an expansion valve or an orfice tube that is plugged up in either case. Both regulate the pressure drop going into the evaporator to set a core temperature. There may be two if there's a separate bunk evaporator. Expansion valves and orfice tubes both have inlet screens. That's the "end of the road" for for compressor guts, provided the screens are not torn or gone.

The orfice tube is just that: a tiny metal tube with a specific diameter mounted in a long plastic frame and wrapped by a filter screen, about the size of a cigarette. On the liquid line coming from the condenser, there would be a fitting somewhere coupled to another tube that's a little fatter the last few inches than the rest. The orfice tube assembly slides into that fat part and bottoms out in it. When you open the coupler and separate the lines, you'll see a plastic nub in the side with the fatter end - that's the orfice tube. If you're lucky it will pull out with needle nose pliers. If not, there's a tool for that - a little like a cork remover. It has a screw shape tool on the end that self taps into the metal orfice and a shoulder that works like a press on the end of the tube to pull the mess out.

An expansion valve looks like a billet block shaped like a rectangle, usually about the same size if you were to saw an inch and a half long end off a 2x4. Sometimes they'll have what looks like a thermocouple on the side. Unlike the orfice tube which is inline on the high side, the expansion valve usually has two tubes in and out (low and high, one each on each side) to permit pressure balancing/bypass outside the evaporator. Usually there is a flange assembly on both sides with a bolt thru the middle to hold it all together.

You have to flush the parts with a solvent that will cut and is compatible with whatever oil is in the system. You didn't say what year, so I'll assume 94 or newer which ought to have R-134a in it, but may have either PAG or Esther base oil. They are not compatible with each other, nor are they compatible with mineral-based solvents (like paint thinner). There ought to be a label somewhere. Look at your condenser and apply some common sense as to whether whatever liquid you find will flush out particles about the consistency of powder up to small crumb sizes, soaked in oil and cooked, completely out clean as a whistle. You'll need to flush out the high side completely or you'll be doing it over and over. That is, from the high side line (disconnected from the compressor for flushing) all the way to the orfice tube or expansion valve (disconnected for flushing).

If it were me, I'd buy a new condenser (don't forget to add whatever quantity of the correct oil per the instructions that come with it) and new expansion valve(s) or orfice tube(s) after flushing only the lines. If the truck is more than 5-6 years old, it probably wouldn't be a bad investment to go to the stealer and get new lines too.

The reciever/dryer is just a big cannister on the low side that has a big bag of dessicant in it to absorb moisture. If it's been a long time (or never) since the system was open, you routinely change it. If you just put a new one in, you really don't need to replace it again if you have to open the system again right away to fix something else you missed.

Sounds like you're trying to save a few bucks so I know I'm not telling you good news. I've repaired 100s of 4-wheeler a/c systems and I will say you have a 95% chance of chasing that problem over and over and only getting luke-cold air on a good day until you either fix it right (not cheap) or trade the truck.

 

About what I just went thru for only about $100 more including your earlier stops. My last trip to the a/c shop was a leak on the low-side line from the expansion valve to the bunk evaporator. When they started taking things apart, every fitting was seized and broke. $1,800 later, ice cold air again. That was after another $1,000 to do the compressor and a couple of lines under the hood a couple of months ago while getting the radiator replaced too. I think the dash evaporator, and maybe one or two hard lines under the hood are the only parts left that weren't replaced.

Knock on wood.