84 300DT AC job

[arew264]

The compressor in my car died. It has been dead for somewhere near a year, and the story as I was told goes like this:
The AC was on, and the compressor started making a moaning noise and leaked all the refrigerant out (it had been converted to R-134).
Since then, the system has been flushed, but a new compressor was not installed. I have a new compressor, receiver/dryer, and expansion valve sitting in the back seat.

I'm a high school student, and I will be driving this car for the next few years, and it looks as though I am going to have to do the job myself because my dad doesn't see it as a priority.

As there is no refrigerant in the system, I should be able to just disconnect the expansion valve and replace it, right?
On the receiver dryer, I am told there is a temperature switch that determines when the compressor clutches in. Would this switch be included on a new dryer or will I have to move the old one over?

IIRC the compressor is in the lower right of the hood, so I would have to put the car on ramps to replace it, right?
What would the procedure be for putting in oil, etc?


I have a basic understanding of how this all works, but I am not sure where to start. Thanks in advance for any help you can offer, I really need it .

[JimmyL]

Where in Texas are you located Andrew?

I think I would go ahead and buy a new pressure switch that goes on the rec/dryer. They aren't real expensive, but if it needs replacing in the future you have to evacuate all your refrigerant, and then you have issues with adding oil, how much, etc.......
Also, if you are going with R-134A or Freeze12 you need to get the pressure switch that monitors high AND low pressures. Same price pretty much.

Non-R12 systems in Texas don't get the most out of these AC systems, but really, they aren't that great to start with. Also, financial concerns do come into play, especially high school students.....
Plus, yall can tolerate a little more heat than we olds.....

[arew264]

I'm in Friendswood, right betweel Houston and Galveston. Excellent schools here

So should I go ahead and order the pressure switch (available from fastlane?) and install the new parts, but wait to charge it until I get the switch?

Yes, I will want to stick with R-134 due to price and because we have gauges and equipment for it. I've never actually worked on an A/C system before, but my dad maintains the A/C on the 3-4 cars we normally have.
The problem here is that he "doesn't see it as a priority", so I have to do it myself. Guess I get the chance to learn

EDIT: I should probably update my signature, I found that my car definitely has more than 138k miles... (the odometer stopped)
Dunno how many it actually has though.

[arew264]

OKAY!
checked Fastlane, and I see that pressure switch. cuts out below 2bars and above 30bars.
Now the only thing I need help on is what I should do for the installation.

[arew264]

*bump*
Still wondering what I have to do to get the compressor and receiver/dryer out and replace them.

[Scott98]

Originally Posted by arew264

*bump*
Still wondering what I have to do to get the compressor and receiver/dryer out and replace them.

You said you flushed the system already, right? Then just remove the R/D and expansion valve. Hold the expansion valve with some channel locks when you loosen the bolts so you don't bend the lines going to your evaporator. Use new O rings on everything. Dip them in oil before you roll them on. Put about 2 oz of oil in your compressor before you install it. Put a plug in the back to keep the oil from coming out until you hook the new lines up. Add oil to the R/D too - about 5 oz.

After everything is together, pull a vacuum with a real vacuum pump (not he HF box) for about 45 - 60 minutes. Then add freon to both the high and low sides with the car off. The vacuum will suck the freon in. Then DISCONNECT THE HIGH SIDE and start your car and run the A/C on high. Feed the remaining freon in through the low side. Cycle your compressor on and off several times to lubricate it properly.

Scott

[arew264]

I don't have it in front of me right now, but the box for the compressor had some instructions for lubricating it...
I'll get it and read them...
1. Replace the receiver drier.
2. replace the expansion valve if malfunctioning or clogged.
3. Replace the "O" rings and or faskets on any fittings or connections open or showing signs of leaks
4. Fill new compressor with oil according to vehicle manufacturer's specifications
5. Install supplemental in-line filter between condenser and expansion valve
6. evacuate the system at 29" of vacuum for a minimum of 30 minutes
7. turn the compressor a full 10 rotations with a clutch spanner wrench prior to engine operation
8. for further information, please read the enclosed instruction sheet

This is basically what you said, but they seem to have a slightly different method for the oil.
Instead of letting it enter during the first few rotations when it's installed, they want you to put it in and turn the compressor 10 rotations...
I'm not sure I understand how that would work. The oil travels with the refrigerant, so wouldn't putting it in and turning the compressor 10 times just pull all the oil through and out the high pressure connection?

Looking at the instruction sheet, the compressor was shipped without oil but designed for either R-12 or R-134, and they say I should use 8 oz of either mineral or PAG oil.
Even though this system was converted a few years back, I should continue to use ester oil, right?

I have the compressor out of the box, and there are two ports on top that are plugged bu rubber plugs. These would be the refrigerant lines, correct?
They are really close together and slightly different sizes, so I would guess the refrigerant lines are both in a fitting that screws in in only one orientation?
Also on top are four holes for bolts. I'm guessing that this mounts sideways so those bolts go on horizontally.

[my123ca]

You should find out first if your new compressor matches the ac manifold that you have in your car. I would remove the old compressor and compare with the new. There are a number of versions of R4 compressor, stepped, non stepped etc. I filled my compressor with 90cc PAG oil thru the low side service port since I did not flush the system beforehand. I also put in 40 cc of PAG oil in the new receiver drier. Find a way to engage the compressor clutch without starting the car and spin the pulley according to the instructions. I dont know if ester oil is compatible with r134. I dont think so but some experts here in the forum should know. I converted to R134 , new drier, expansion valve, parallel flow condenser, used but working compressor, two fan system. Im still not satisfied with the temp. If I were to do this again, Ill go back to R12.

[arew264]

Okay, I will have the system apart at some point in the next few days, but I have to wait because I have to order that low/high pressure switch that was mentioned. I just have the low one right now.

So, in the way of Oil, I should use ester, and I can either put it in the pump and turn the pump or distribute it throughout the system.

The one thing I'm still not too sure about is pulling a vacuum for an hour or so. Previously I thought this was to make sure the system holds pressure, but from the looks of it, air should leak in during that time and the pressure should fall some and cause me to have to reevacuate, right? IIRC where I read about it, they said it should hold the same pressure for about 10 minutes but that the pressure will fall over time.
Aside from that, theres the issue of tools. When I first thought it was just pulling a vacuum to see if the system held it, I thought, "Oh good, I can use the MityVac!". Now I'm thinking, "Oh crap, do I have to use the MityVac?"
What should I use to evacuate the system? My dad has a compressor, but it has no intake hose...

[dmorrison]

Take the time to go to the library or Barnes and Nobles and read a book on AC systems. "Haynes Automotive Heating and Air Conditioning" is a good book, It will answer a lot of your questions. It will take a day of your time but as I said, Answer a lot of your questions. Our AC systems use a expansion valve so don't waste time reading about the other types of systems.

Technique

Since the system is converted to R134a your pressure switch on the receiver/dryer (R/D) should have been changed out. If it is not then replace it as advised.
Remove the old R/D and bolt in the new one. LEAVE THE CAPS ON THE NEW ONE UNTILL THE LAST MINUTE. So the desiccant bag is not used up in the humid Houston air.
Replace the expansion valve anyway. IF blocked you will not know until the system is all buttoned up and charged. Then if it's bad it will not work and you will have to discharge the system and recharge it. $30 of freon gone vs. the new expansion valve.
Always use new O'rings and oil on them. Use PAG oil only, not mineral oil

Everything in your AC system uses SAE wrenches not metric.

Compressor. Located on the right front bottom of the engine ( looking forward from the drivers seat). Removing it requires 4 bolts to be removed. 3 are in the back of the compressor, the 4th one is on the left top/side of the assembly that applies tension to the compressor belt. MAKE SURE YOU KEEP TRACK OF ALL THE BOLTS, NUTS SPACERS AND WASHERS AND THEIR ORDER INSTALLED. Access will have to be from below for 2 of the bolts as well as removing the compressor via the bottom of the car. It is a little heavy and bulky. Disconnect the manifold hose ( the one that connects to the back of the compressor ) first, keep track of all seals etc. But I find it easier to connect the manifold hose to the new compressor while it is sitting on the bench, not in the car. If you choose to leave the hose installed, you can poor the oil into the hose where it connects to the high pressure hose as it continues form the manifold to the condenser. New o'rings and oil after disconnecting the hoses.

Oil in the compressor. You install the oil and then turn it by hand because the compressor cannot handle liquids at full speed. It will ruin it. So you install the oil, rotate the compressor 10 times and the liquid oil will be past the compressor and into the manifold hose.

Oil in the system. If the system has been completely flushed all the oil is out of the system and you will have to add the amount specified for your system. split it up into various parts so it is distributed.

You must evacuate the system to remove the moisture. The longer the better. No you can't use a mity vac. It should be pulled to 29" of vacuum. that is why there is the negative side of the AC gauges so you can measure it. Rent of borrow a 2hp unit if you can. The gauges are connected to the high and low side, connect the vacuum pump to the center hose on the gauges and let it run for as long as you can with both high and low side valve open. Close all hoses and let the car sit overnight. The vacuum gauge reading should not move. If it does you have a leak in the system.
If so tighten each connection and check the compressor to manifold connection.

If it holds the vacuum. Then add a can of freon. Do this by attaching it to the center hose of the gauge set, still connected. Open the low and high side. Open the can valve and allow the vacuum to suck the freon in. The can will get cold. Close your gauge valves after a while. One can should be enough to pressurize the system to allow the compressor to kick in. Now you must close the high side valve on the gauge set. THIS IS VERY IMPORTANT OR THE CAN MAY EXPLODE.
Now to add the rest of the freon charge. NOTE- do not allow liquid freon to enter the system, Which means do not turn the can upside down. You should only allow gas freon to be sucked into the system from the top of the can.
Start the car and run the engine at 2000RPM. Open the low side gauge valve and the freon can valve. Allow the rest of the freon in the can to be sucked into the system. You can swirl the can to see if its empty, you'll feel the liquid in the can. When empty close the gauge valves and freon can valve. Connect the second can and open the freon valve and then the low pressure side of the gauge set. Allow the freon to be sucked into the system.
You are only going to add 80-85 % of the normal R12 charge when using R134a in a R12 system.

ALWAYS wear safety glasses and gloves the freon can damage eyes and skin very easily.

To help the freon evaporate you can place the can of freon in a warm container of water. Warm not hot. If you can't keep your hand in the water then its too hot.

Dave

[arew264]

Well, an update and an urgent question.

As it turns out, the system was not flushed, but all the freon leaked out. This would leave the oil still there, correct?

So far, I have installed the compressor, poured about 8 oz (maybe a little more) down the suction like (you can separate the rest of the hose from the metal piece that goes to the manifold) turned the compressor about ten times, and gotten the belt on and everything back where it should be and connected.
I then pulled a vacuum and checked - had a small leak where I didn't have the top right hose on the expansion valve tight. Got that fixed, and then vacuumed it out. Only got to about 20 inches, but I charged it with a can of freon to 30 lbs three times while trying to get the leak fixed - it's easy to charge with some freon to hear the hiss and find the smell.
I figured the 20 inches would be ok because the freon charges would have removed a good bit of air. I then kept it vacuumed for about an hour (no leaks) and broke the vacuum. I then added a can of freon and fired up the compressor. Added 1 more, took it for a drive to make sure it was behaving and cooling correctly, and tried to add one more to get it charged to where it should be.
At this point, it should have been just under charge, correct?
The issue was that at idle I had 80 lbs of pressure, which got down when getting to 2000 rpm, but not nearly down enough.

My question is this. When the freon leaked out, it should have left the oil behind, correct? This would mean I still had oil in the system.
I'm worried that I somehow messed up with the oil. The manufacturer (GM) wanted 8 oz of oil in the compressor and the compressor turned by hand 10 times, which I did. With the preexisting oil still in the system, everything should have been good, right? The fact that the compressor hasn't gone south seems to point that I did it right, yet I'm getting at max vent temperatures down in the 60s when driving.

Another note, when I was first charging it and I had a thermometer in the vent, the temperature got down to about 65*F ish.
After the drive (after I added most of that last can of freon), at regular idle, I was getting outside air, basically. It got somewhat better if I stepped on the gas some, but it didn't seem to be cooling as well as it did before.

What gives? Something really wierd is going on. Any suggestions as to what or how to troubleshoot it?

[arew264]

bump?
Did I just overcharge the system?

[Bajaman]

Since you did not flush the system, you don't know how much oil was in there, nor did you clean out the bits of the last compressor which could plug up the expansion valve, and or damage the new compressor. This is why you always read about extensive flushing... By the way are you using 134a? You should be aware of compatibility issues with different refrigerants, oils etc. Do a search, I have read this information countless times on this forum.
bb

[arew264]

I do know about the compatibility issues. I used ester oil and r-134, and this system was flushed and converted several years back.
Yes, I know it was not flushed and it should have been. My dad mentioned something about it, and I thought he said he already flushed it.
The trick is that this system didn't die like it was just a compressor failure, it seems it was a freon leak (possibly in the compressor) that just drained all the freon.
As it is, the new compressor seems to be fine, and given that we got a little over 8 oz of oil at the start, and there would be atleast some left in the system, it would seem that everything is fine but we just need to get the freon levels back where they should be. I'll have to get my dad to check the high side pressure as well during this.

As I said, the new compressor seems fine, and I doubt the old compressor put any metal shavings into the system (I'm not sure it ever actually failed, we just got a leak that seemed it was in the compressor).
Given that, would it be alright if I just installed an inline filter on the suction line to catch any remnants before they go to the compressor?

Just a few comments,
With the conversion a few years back, did you replace the condensor? This will make a huge difference. The low pressure switch, make sure it is for 134A or is adjustable. The vacuum you pulled at 20 inches was probably not sufficient and you may still have moisture in the system. The reason for going to 29 inches or more is because water will "boil" at this level of vacuum and I may be wrong but I don't believe that 20 inches will do the trick. You are not just trying to eliminate "air" from the system.

For what its worth I converted my 83 300SD a few years back and consistently blow 38 degrees in 95 plus weather with high humidity so I know its is possible to do so.