maybe368

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Well I have been going through some trials and tribulations with the old girl that required me to rebuild the entire ac system. It applies to my 1990 W250. but with some differences, it should be helpful for the later trucks as well. I believe, but am not sure, that 89-91.5 are the same, with some differences in later years. If this is not correct, please correct me. So...As always NEVER WORK UNDER A VEHICLE THAT IS SUPPORTED BY A JACK ONLY. Always wear safety glasses, especially working around high pressures, solvents and other nasty stuff.

I am converting to R134A and will include information on that, but it is not necessary. I accumulated parts, including: A complete kit that included the compressor, expansion valve (not correct, more on that later), seal kit, filter drier and 8 ounces of PAG oil (compatible with R134A), separately, low pressure cutoff switch, all the quick connect adapters for the R134A conversion, nylog (a sealer/lubricant, Thanks rrgrassi ) and new hoses. The hoses were made by a local automotive ac shop, they just use your existing hose fittings and braze them on to new crimp connectors. They fit beautifully. I also bought freon recovery equipment, mostly because I can't bring myself to bleed the refrigerant into the atmosphere, but that is just me, you can follow your conscience. Any ac shop will recover it for you for a fee (of course). Let's get started...

First off, disconnect the negative battery cable, remove the air tube from the air cleaner to the turbo, the serpentine belt and remove the oil filter. You could remove the fan and shroud, it is not necessary, but would make the job easier. I also did not take too many pics during dis-assembly, because I did not want to dirty my camera, so don't be surprised if you see new parts on dis-assembly. Disconnect the electrical connections , there are 2, There are 2 bolts in front of the compressor that need to be removed, you need an open end wrench. It would be easier to get these out without the shroud, but it is not too bad, a quarter turn at a time. There is also a bolt hidden below the water pipe, see pic. This is why you need to remove the oil filter. Also to get access to the top on the compressor and the manifold hose connections. There are 4 bolts holding the compressor underneath, Mine is missing one, I'll find a replacement tomorrow...Continued

maybe368

The wily dodge engineers gave us a nice split bracket, making the job possible. I could not get the manifold hose connectors off, so I just pulled the manifolds off of the compressor. With out the manifolds, or with them if you can get the hoses off (I was afraid of bending and damaging the manifolds) you just slide the compressor out the bottom, pulley side first. You can see the broken wire that caused all this. Once the compressor is out, you can remove the hose system. It is pretty easy. The expansion valve is held on by 1 bolt in the middle. You may need to tap on the valve to break it free. There is a nut that holds on the condenser side....continued

maybe368

The hoses are held on to the filter dryer by a single nut on each side.The hose connections to the manifold are in kind of a tough spot, but you can get wrenches on them. I could not get them off without damaging the manifolds, so I just removed the manifolds from the compressor. Be very careful not to lose the little plastic guides as you remove the manifolds. It all comes off pretty easy. I had new hoses made at a local shop. It was not cheap, 49 dollars for each rubber piece, there are 5... You can then remove the expansion valve. retained by 2 torx head screws. The low pressure cutout switch is on the fender side...continued

maybe368

Once it is all apart, it is important to flush out the condenser and evaporator, especially if you are converting to R134A. I rented a unit for ten bucks. Watch out because it operates at 75 to 100 psi. I was working alone so it was difficult to control all the moving parts. It is best to flush from low to high, to loosen up the crud, then top to bottom. Overall, pretty easy...Continued

maybe368

I always use blue locktite on bolt threads, mostly because it seems that the factory did. I used nylog sealant and lubricant on all the seal surfaces and the threads. Thanks again rrgrassi. I almost missed 2 old o-rings, be careful of this, could be bad. I lightly sanded the seal surfaces on the manifolds, to clean them up. When you reassemble, put the plastic guides into the gasket first, them put them in place. Be careful when you are removing the seals on the new compressor, mine was slightly pressurized and sent pag oil into my safety glasses, Also, some compressors come with 8 ounces of oil in them, but others come with just enough to test the compressor at the factory. It is best to pour it out and replace with the correct amount, 8 ounces in this case...Continued

maybe368

Reinstalling the compressor would be really easy with 2 people, one above and 1 below. Unfortunately, I am working alone. I was able to kind of balance the compressor up there, then slide the half bracket up in position. You need to put the 2 screws toward the rear of the truck in as you put in the half bracket. Use the 2 bolts to kind of hold it in place, then put in the single bolt on top, under the water pipe. Leave it loose for now. Install and tighten up the 4 bolts holding the compressor to the bracket, remember that I am missing 1. Don't forget to tighten up the top bolt on the half bracket. Then replace the 2 bolts on the top/front of the compressor, see the foto in the first post. All done below...Continued

maybe368

Install the low pressure shut off switch into the expansion valve. This part was incorrect in the kit that I bought, it has this switch on the right side and interfaces with the fan housing. The part# of the incorrect part is ex9414c. Fortunately, there is an ac shop close by and they had the correct part, although their book also listed the incorrect part. He just went through the book until he found it. It is part# 3411283. Then just continue connecting all the hoses, remember to use the nylog on all the o-rings.gaskets and threads. The filter dryer is a little floppy on its mount, so I had to take a long, stout screw driver to lever against, again this would be easier with 2 people..Continued

maybe368

I then used my cheapie harbor freight vacuum pump to evacuate the system. It held the vacuum for around an hour and a half, woo-hoo, no leaks. I then charged her up, I didn't worry too much about the numbers, I just watched the sight glass and the temperature. I understand that you don't want to take R134A to a clear condition in the sight glass. This is because it operates at higher pressures, so I understand. I fed in small amounts of gas until the sight glass had a cloud go by once in a while. Make sure to start the truck and turn the ac on max. The compressor will not be spinning, because there is low pressure in the system. Just start feeding in the gas and when there is enough pressure the compressor will start spinning. Some people jump across the low pressure switch wiring, but it is not recommended. It is in a real bad location on these trucks anyway. She sure is blowing cold. It was a very humid day (for us), which is not ideal for charging the system. You should not invert the freon tank and introduce the liquid, as this can liquid hammer the compressor to death. I am by no means an expert on ac, so please feel free to correct anything I may have messed up. All I know is that my air is blowing cold...and that pleases Mark...

jughead

too late now but i would have suggested using ester oil instead of pag. less issues with hoses

maybe368

Thanks for the info. I just used what came in the kit, although I recall reading a recent thread where this was discussed, but being the basically lazy one, I went with the pag . What kind of issues are there with the hoses? Thanks...Mark

jughead

ester oil is compatable with 12 and 134 if one doesnt totally get all the mineral oil out it re-acts with pag and some say forms an acid that works on the old non-barrier hoses which have a rather hard time containing 134 anyway.

maybe368

Yeah, I read about that problem with the hoses in a recent thread, that is why I replaced them. I was also aware of the ester oil, but I was a little worried about the warranty. I read somewhere that up to 20% mineral oil left in the system is ok, sounds like a lot to me. I was a little shocked at the price of the hoses, 50 bucks per rubber hose and there are 5 of them. I asked why the short ones are the same as the long ones he said that they don't even charge for the hose, it's all labor. Well worth it considering that I replaced all the other components. These are the conversion compatible non-permeable hoses...Mark

Philip

Thanks for that expansion valve part number number. I hit the same problem last week on my truck.

maybe368

You are certainly welcome. I have a feeling that every ac parts catalogue out there has this same error. As a side note, the belt tensioner started squeaking after the ac install. No problem, 15 minute job, right? That is what I thought, the new tensioner came with a 1/2" opening to put in a ratchet to lever it in. Well, I don't know about you, but it was hard enough to slide a 3/8' into, 1/2" is IMPOSSIBLE. I even loosened the shroud up and it cleared space for everything, except the hole . Some idiot aftermarket parts designer thought that if 3/8" is good, then 1/2" is better, NOOOOT!!!!!. I am going to try and get a dremel in there to cut out access space for the tool. What a bunch of dumb bastigeges......Mark

Philip

The place I bought my kit from has the correct number now. I had sent pic's on Friday of the orginal block to the new block. He hadn't found the correct one as of this morning. I called and talked to them. When I gave him that number. He brought it up and compared the pic's of mine.

Mine should be in by Friday.