I just replaced the a/c compressor, drier and expansion valve on my 85 300DT sedan. I used the Diesel Giant DIY for a guide (there wasn't one on this discussion), and a friend who'd done this kind of work before. I plan to have the system professionally evacuated and recharged now that the replacements are installed (see my concluding paragraph for more about how the operation was performed).

I have a few questions regarding oil and refrigerant:

1. I left the electronic cables disconnected from the compressor. Is it safe to drive it like this without any charge?

2. I put 4 oz. of oil in the compressor before mounting it as it instructed on the DIY page. When I went to mount the compressor, most of this oil spilled all over my hair (lol). Q: Do I need to ask the person who evacuates and recharges the system to add extra oil to the system/compressor?

3. I'm debating the R143a vs. R12 refrigerant. I know that the R12 is cooler, but I'm one of those hippie types that doesn't want to use the R12 for environmental reasons. Will it really make that much difference?

FYI for responses: I did flush the system with one can of flush, and evacuated it with an air gun until no liquids came out from any of the lines. I also replaced all of the o-rings using oil to lubricate them. I also used the 100 oil for the 134 oil to fill the compressor and drier thinking that I would be continuing with the R134 refrigerant (the car is already retrofitted). Lastly, I used a compressor from ********AZ that is not the factory one-I wish I'd read the posts about using the MB one prior to the install (it took around 8 hours to do all the work, and I'm not going back now!)...

Yes, if oil spilled out make sure you replace it before putting the system in service. I'm assuming that when you refer to 100 oil you mean PAG 100 which is made for R134 systems. If you were going to use R12 you would stick with the original mineral oil. Make sure you use the correct amount of oil and that the oil and refrigerant are compatible.

If you are going to run the engine that is fine as long as the compressor is not engaged. Leaving the electrical connector unplugged will accomplish that but personally I would leave the connecter attached and take the drive belt off.

__________________
'82 300D - Light Ivory, 2nd Owner (Back in the wind April 2013!)

'95 E300D - White, grey interior. (Suffering from stuck/broken glow plugs)

Deuteronomy 22:4-
"Thou shalt not see thy brother's ass or his ox fall down by the way, and hide thyself from them: thou shalt surely help him to lift them up again."

Thanks fdanielson for your reply. Do you know if I need to get down under the car to add the oil, or can if fill it from the R134 fill valve? I don't want to have the mechanics add R134+Oil in the can if that's not going to be enough...

Is your car fitted with the R4 compressor ?
If yes, it has no sump... so the oil needs to be split around the system if possible. Probably too late for that now... probably better to add it at the 134 valve now which will accomplish that somewhat...
Did you flush in sections as you had them apart to renew the o-rings ?
If you have the R4 compressor... Did you use the old manifold ? The AC manual says to put a new one one as it can not be cleaned ... this means that if the reason your compressor went bad was lack of cleanliness by the former owner or AC work you may be putting your new compressor at risk.

Why don't you put your location up in the right hand corner..... this can affect answers to AC questions... R12 in Texas, 134a in Maine....that sort of thing....LOL

Adding the oil to the high-side service port would be best. But how much? You'll just have to guess.

I do hate to tell you this, but you should not have installed the dryer yet. It should be installed only when you are ready to evacuate the system. Hopefully it will not have absorbed much water yet, which would mean that you are fine.

What kind of oil did you use?

Where's Jimmy?

You cannot evacuate with an air compressor blowing out the lines. The flushing should have been done in stages, IE, the evaporator, the condensor, and all the lines.

Since you already hooked up a drier, and it has been on the car, you will need to replace the drier again. Like said earlier, the drier is the last thing to install, then the car needs to be connected to a vacuum pump immediately.

Did the replacement compressor have flat ports or stepped ports?

__________________
RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

99 W210 E300 Turbo Diesel, chipped, DPF/Converter Delete. Still needs EGR Delete, 232K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Gone and still missed...1982 w123 300D, 1991 w124 300D

I thought what he meant was that he used compressed air to blow out the liquid flush material..and will be having a pro vacuum the system.

I totally agree that the drier needs to be put on new seconds before the vacuuming is to begin... it just sucks up moisture, has limited capacity, holds the moisture below oil and thus can not be renewed by vacuum as a result.. and once it gets full of what it can absorb then it can do no more...and your system is at risk of oil and moisture mixing and forming acid.

"FYI for responses: I did flush the system with one can of flush, and evacuated it with an air gun until no liquids came out from any of the lines. "

I saw this as well, and is where I based my response.

__________________
RRGrassi


70's Southern Pacific #5608 Fairmont A-4 MOW car

13 VW JSW 2.0 TDI 193K, Tuned with DPF and EGR Delete.

99 W210 E300 Turbo Diesel, chipped, DPF/Converter Delete. Still needs EGR Delete, 232K

90 Dodge D250 5.9 Cummins/5 speed. 400K

Gone and still missed...1982 w123 300D, 1991 w124 300D

He used a word we use for vacuuming.... " evacuated ' ....but your reading of " air gun " as meaning an air powered venturi type vacuum did not mesh with the rest of the sentence... but forcing the flush out of the lines it was in with a normal hand held ' air gun' did to me...
I am sure he will clear up what he meant... and use ' blew out' instead of evacuated next time... LOL

OK, lots to clarify. 1. I added my location, you should see it now. I gather since I've already put PAG 100 oil in the system, 134A is my only option. I'm okay with that I think. 2. It is an R4 compressor. I understand that it would be difficult to get the oil in there now. I know some of the 4oz I added is still in there, but not much. 3. Yes I flushed the system in sections with AC Flush, and replaced all of the o-rings and lubricated them. 4. Not sure what you mean by 'manifold'. 5. I DID install the drier already. On top of that, I filled it with PAG 100 oil (till full) before installing it. Not sure how this will effect what you mean by getting water in it, acid etc. 6. The replacement compressor had stepped ports, if by that you mean that one was slightly deeper than the other and required a slightly different width bushing. 7. I did mean to say that I flushed the car with AC Flush, then using an air gun 'blew out' any remaining fluid (in sections, replacing and lubricating o-rings).

SOOO...if I have to replace the drier, it isn't the biggest deal in the world, 30 bucks and 30 minutes isn't going to kill me. But why would the DG site say to fill it with oil if it is supposed to be dry when you evacuate it?

I hope this clarifies enough to confirm, a. that i need to replace the drier, b. that I can still use the car without burning up the compressor until the new drier comes and I can get the car evacuated and filled with R134a.

Since the DG site recomends 4oz of oil in the compressor, I guess i'll just ask that they add 4oz of PAG 100 through the high valve when they start to fill...

Thanks again all, and I'm sorry I thought I was being more concise than I was. I didn't mean to baffle ya'll. Cheers!

a small amount of oil needs to be placed in the compressor suction port. NOT the high side... oil needs to get to the compressor.... YOU FILLED THE DRIER?????
um, how much oil does it hold? I think the entire system is only supposed to have 8oz of oil. and if you live in tucson... you're going to NEED to replace your condenser. 134 is totally incapable of cooling your car in AZ... with that condenser. if you install a parallel flow model of adequate size you should be OK.

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 560SL convertible
1987 190D 2.5-5SPEED!!!

1987 300TD
2005 Dodge Sprinter 2500 158"WB
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

So, it looks like I've got what I need to go from here, and john I'll look into the parallel condenser, though I've seen the DIY for replacing that part and it looked like a good enough reason to go with R12. It's really not that much work to replace the drier and blow out the lines again, and then to have the system evacuated. Thanks for all your help (again)! Cheers!

By ' still use the car' until the dryer comes in... I assume you mean NOT activating the compressor...either by leaving off the belt..or not hooking up the electrical wires to it ?
I would not allow that oil in the dryer to be forced into the system. It will be pushed to the evaporator ( if the back pressure does not blow your condenser ) ...and it is usually not even flushed... so in changing oils several times you are risking mixing the oils bigtime.... no one that I know of suggests that is good. Remember, the oil circulates around the system by being mixed in the refrigerant vapor... particularly for our non sump R4 compressors... if the oils mix and gell up enough then your compressor has no lubricant to work with.