evaluating an AC compressor when system is currently discharged - Page 5 - PeachParts Mercedes-Benz Forum

BillGrissom · #1 05-10-2018, 01:08 AM

Be sure to use HBNR O-rings, which are usually green, but sometimes blue or red. I would expect the "R-134A" expansion valve would work fine. Main reason is because of how it works - it varies the opening to maintain a fixed downstream temperature for the evaporator. Some cars (old GM) had just a fixed orifice there. Other reasons are that one can convert from R-12 to R-134A without changing the expansion valve. I use Duracool refrigerant in all my cars now, including my 1996 & 2002 which were originally R-134A. I didn't change the expansion valves or replaced w/ a new listed one, and they all cool fine. Hydrocarbon refrigerants have very similar pressures as R-12 (indeed run slightly lower pressures and more efficient). No need to worry. A good guess as to why it is marked "R-134A" is to assure you that any rubber seals inside are compatible w/ R-134A.

kuene · #2 05-10-2018, 10:16 AM

thanks Bill.

OK - so even if I were to keep the original expansion valve, I'd want to replace the o-rings? I wasn't positive there were o-rings in those connections or not.

If I have the original out and in hand - is there a visual inspection or other kind of basic test I could do in order to ascertain it's working condition?

kuene · #3 05-11-2018, 12:17 PM

picked up my 4 seasons reman heavy r4 compressor today. there is a plate over the in/out ports and a sticker mentioning that a few ounces of oil were added.

if guess i'll know when I take the plate off - but if the unit did not come with any sealing washers, would it possibly be the older o-ring type?

I'm going to dump that oil and use my r12 compatible ac oil. I'm just hoping I don't need to hunt down sealing washers now too...

ROLLGUY · #4 05-11-2018, 01:07 PM

Quote:

Originally Posted by kuene

picked up my 4 seasons reman heavy r4 compressor today. there is a plate over the in/out ports and a sticker mentioning that a few ounces of oil were added.

if guess i'll know when I take the plate off - but if the unit did not come with any sealing washers, would it possibly be the older o-ring type?

I'm going to dump that oil and use my r12 compatible ac oil. I'm just hoping I don't need to hunt down sealing washers now too...

I believe the heavy compressors were all o ring. When the R4 first came out, they all were o ring, and had the big clutch. The second generation R4 had the washers and the smaller clutch. I am not sure, but it may be possible to get a reman unit with washers or o rings and the heavy clutch.

vstech · #5 05-11-2018, 01:33 PM

Quote:

Originally Posted by kuene

picked up my 4 seasons reman heavy r4 compressor today. there is a plate over the in/out ports and a sticker mentioning that a few ounces of oil were added.

if guess i'll know when I take the plate off - but if the unit did not come with any sealing washers, would it possibly be the older o-ring type?

I'm going to dump that oil and use my r12 compatible ac oil. I'm just hoping I don't need to hunt down sealing washers now too...

all oils are R12 compatible... but R12 can use mineral oil... 134 can't...

funola · #6 05-11-2018, 03:26 PM

The reman 4 Seasons heavy R4 that I bought had o-rings. Do not remove the plate until you are ready to charge the system, it provides a pressurized seal. Under the plate should be o-rings. You can re-use them (the ones on mine were black) or replace them with better HNBR o-rings (what I did).

BillGrissom · #7 05-12-2018, 02:12 AM

I would drain out the oil it shipped with, flush in a little new oil and drain again. Most "for 134A" compressors ship with PAG oil. While compatible w/ R-12 or HC refrigerants, it absorbs moisture which can cause internal corrosion. R-12 mineral oil is getting hard to find, and must be a special "no wax" oil for AC. For probably the same price, you can buy Hella PAO 68 oil (ebay or Duracool's "Oil Chill"). Most come w/ uV dye. It doesn't absorb moisture and is compatible w/ all other AC oils and refrigerants. It is also claimed more efficient, by better staying in the compressor where it is needed, instead of in the condenser and evaporator where it decreases heat transfer. That might help R4's last since they have no oil sump and need to hang onto all the lube they can.

kuene · #8 05-12-2018, 10:10 AM

I have some “no wax” ac oil (that says it’s for r12 specifically) that I found at a Napa (had been special orders for another guy who didn’t pick it up). I was going to use this after draining out the shippers oil. I still have much to do - flushing evap, condenser and hoses, replacing orings and maybe the valve. Removing and installing new compressor - this part just seems like a bear.

So I can leave the cover plate on the compressor and hook up the hoses/manifold after I have it fully installed and belt on?

ROLLGUY · #9 05-12-2018, 10:29 AM

Quote:

Originally Posted by kuene

I have some “no wax” ac oil (that says it’s for r12 specifically) that I found at a Napa (had been special orders for another guy who didn’t pick it up). I was going to use this after draining out the shippers oil. I still have much to do - flushing evap, condenser and hoses, replacing orings and maybe the valve. Removing and installing new compressor - this part just seems like a bear.

So I can leave the cover plate on the compressor and hook up the hoses/manifold after I have it fully installed and belt on?

The instructions for installing an R4 usually say that you need to rotate the compressor to distribute the oil before installing it, so it does not start up dry. You may find that the compressor will not turn, no matter how hard you try by hand. There is a tool made for turning the compressor. This requires the removal of the sealing plate. Please check out the installation instructions, and follow them to the letter. So many things that are done/not done can void the warranty, so be very careful. Yes most auto parts stores will take any part back even if it looks at you cross-eyed, but the labor involved in R & R'ing one of these compressors is not worth it if not installed properly.

kuene · #10 05-12-2018, 11:13 AM

That makes sense. I’ve seen some interesting methods to rotating the new compressors by hand to circulate oil without the tool. But maybe I should just get one. They are cheap and prob have other creative uses.

funola · #11 05-12-2018, 11:33 AM

You do not need a special tool to turn the compressor. Use a socket/ ratchet on the center bolt. If you don't have the deep socket, apply power to the clutch and turn it by hand. If you need more leverage, use a rubber band type jar opener/ torque multiplier.

Change/ flush the oil in the compressor immediately before you install it. I used Behr/ Hella PAO 68 oil with premixed dye for R12

BillGrissom · #12 05-14-2018, 12:05 AM

I had a new R4 and was easily able to turn the shaft by hand. I did that on the bench, and it helps force all the PAG oil out. Otherwise, you could install it, tension the belt, and use the engine to turn it over before you bolt on the hose manifold.

Don't need to use the starter, just put a wrench on the bolt on the power steering pump to turn the engine over by hand. As many times as I've done that, I just thought that a diesel could theoretically start from turning it by hand. But, without the glow plugs and turning so slowly, I doubt it could ever start. You will need to actuate the AC clutch, which you can do by pulling the relay and jumping terminal 30 to 87 in the socket w/ a wire.

Most people bolt on the tubes and fill the oil by pouring it down the suction tube, which can be disconnected just above the compressor. If you try to pre-fill, the oil will just run out until you get the tube manifold on. I would rotate the engine (or just compressor) while doing this, to insure you don't hydro-lock the compressor. Actually, that sounds impossible since the outlet valves are just flapper plates which can always open. But, seems smart to distribute the oil regardless.

kuene · #13 05-14-2018, 09:23 AM

I can turn the face of the thing by hand. Is the cprr correction direction to turn clockwise? (If I’m looking at compressor while standing in front of engine).

I’m just waiting for my flush to arrive before tackling the job. Couple questions remain during prep:

1) I want to test the power runing to the compressor clutch. I will jump at the relay - which relay box is this - on the front end of drivers side fender?

2) I was doing a dry run, planning our access to the bolts holding the compressor. Are there 4 or 3? Do I need to remove anything else from engine/compartment to actually remove/install the compressor? If not out of absolute need, is there a thing or two I could remove (without needing to drain coolant) that would make the job or access easier?

3) I’ve not really messed with my belts yet. Can I just approximate the tension when I put the belt back on, or do I need to deal with that more precisely? I’m hoping that in loosening the bolts on old I will be able to determine how this tension is adjusted.

kuene · #14 05-16-2018, 09:42 AM

just trying to bump this a little but don't want to be annoying.. if anybody can provide insight into one or two of these questions as I prep for compressor R&R. I can't thank this community enough for all the help I've received over the last couple years - just want to throw out that genuine appreciation!

Quote:

Originally Posted by kuene

I can turn the face of the thing by hand. Is the cprr correction direction to turn clockwise? (If I’m looking at compressor while standing in front of engine).

I’m just waiting for my flush to arrive before tackling the job. Couple questions remain during prep:

1) I want to test the power runing to the compressor clutch. I will jump at the relay - which relay box is this - on the front end of drivers side fender?

2) I was doing a dry run, planning our access to the bolts holding the compressor. Are there 4 or 3? Do I need to remove anything else from engine/compartment to actually remove/install the compressor? If not out of absolute need, is there a thing or two I could remove (without needing to drain coolant) that would make the job or access easier?

3) I’ve not really messed with my belts yet. Can I just approximate the tension when I put the belt back on, or do I need to deal with that more precisely? I’m hoping that in loosening the bolts on old I will be able to determine how this tension is adjusted.