air conditioning questions - PeachParts Mercedes-Benz Forum

luvmysd · #1 04-14-2003, 03:41 PM

Hi everybody my compressor bit the big one last fall and now I have a rebuilt one to go in its place. My question is how much oil is soposed to be put in the compressor, I have a can of pag oil that come with it. Also I was wondering if this system has an orifice tube, and if so where is it. I have also bought a reciever/drier for it.
Thanks

David

#2 04-14-2003, 04:39 PM

To begin with do NOT use the PAG oil in your system. PAG is for systems that were originally 134 from the factory.

If you are using R12, use mineral oil, if you are converting to 134, use ester oil. Since you have blown a compressor it will be ABSOLUTELY NECESSARY to THOROUGHLY flush the system, then flush it over again, followed by another THOROUGH flushing. Failure to THOROUGHLY flush a system after compressor failure is a guarantee for another failed compressor.

If the compressor is being replaced ONLY because of a blown seal, then you can be a little less fanatical about flushing. If you are changing to 134, flush it thoroughly anyway.

I am pretty sure that your system requires 6 oz., but you can verify this by checking the information at www.aircondition.com.

BTW, this is not an orifice tube system. There is an H block type expansion valve on the evaporator underneath and behind the glove box.

Good luck and happy flushing,

luvmysd · #3 04-14-2003, 05:01 PM

Ok Thanks
BTW the system was converted to 134a before the compressor seized do I still use ester?

leathermang · #4 04-14-2003, 07:57 PM

http://www.ackits.com/

these people have a forum on auto ac stuff...

#5 04-15-2003, 07:53 AM

Yes, you still use Ester. As I said, PAG is ONLY for cars that came from the factory with 134. When putting in either of the 134 oils it is very important to pour in the oil, immediately close the container and get the system together as soon as possible. These oils are very hygroscopic, so they soak moisture out of the air at a rapid rate. Not a good thing.

Do you know if the system was thoroughly flushed at the time of the conversion? If not, now would be the perfect time to thoroughly flush the system. If the compressor internally failed, it will be ABSOLUTELY MANDATORY to thoroughly flush the system.

I just reread your original post and see that the compressor SIEZED. This means that you MUST THOROUGHLY FLUSH THE SYSTEM EVERYWHERE!!!!!!!!

Also, you should check with your automotive a/c supply and see if they can supply you with a suction side filter. This will filter everything just before the compressor inlet. You still need to flush the system though.

Good luck,

gsxr · #6 04-15-2003, 03:05 PM

If your compressor seized, and you don't flush like Larry says, you will be doing the job all over again shortly. And since you have to flush anyway, I'd take the opportunity and convert back to R-12 while you have the chance to re-fill with mineral oil. PAG/POE are nasty garbage, as is R-134a. Jim (?) on the MBZ email list considers all three to be "contaminants" to an A/C system and I agree!

#7 04-15-2003, 05:01 PM

I also would recommend reverse converting. Some cars do okay when converted to r134, but the 123 and especially the 124 MB's are NOT good candidates for conversion. This would be a great opportunity to do this.

I have reverse converted one vehicle with great success.

Good luck,

md21722 · #8 05-06-2003, 05:05 PM

Larry,

When we talk about MINERAL OIL - is there "one size fits all". My W124 has a Nippondenso which takes ISO 46 oil to my knowledge, but I can't seem to find a specific viscosity for mineral oil other than "recommended for GM" which make me think its too thick?

Also, have you ever flushed a W124? Removing the expansion valve does NOT look like fun! Have you charged up the system with some nitrogen or used it as a final flush?

Thanks,

leathermang · #9 05-06-2003, 08:36 PM

Note : Nitrogen is available in 'dry' or 'not dry' containers.. one needs the dry one to use it as a flush for air conditioner systems...

These really tech questions , like about the oil, can also be asked of the place in San Antonio which TCane suggested ...

Lyle Ac I think.. will come back and edit when I find it.. if that is not correct...

CSchmidt · #10 05-07-2003, 10:47 PM

Folks,

It appears my a/c compressor died tonight also. I need to debug more to confirm, but it appears so. Must be the season.

Any preferred sources? (87 sdl, I checked fastlane and they don't carry it). It appears to be a Nippodenso 10p15c model, and that appears to be used on many cars. I would guess the Mercedes version is specific? Is new available or only rebuilt?

I got the hint about flushing... I will ask my buddy to assist. He spent 20 years in Dallas and was doing A/C work for a long while. He has the tools, guages, vacuum pump....

Anything special needed? Compressor, oil, still deciding on r-12 retro vs staying with 134 (it was converted 5 or 6 years ago), receiver dryer, fastlane said a r/d switch is needed? Any special O-rings?

The good news is it means a road trip to my buddy's place and most likely a beverage or two when we're done. BTW - I've been working on him about diesels, and he just bought a new Ford Superduty with the 6.0 L engine. Quite a machine! Tows his horse trailer like it isn't there.

Thanks again for the guidance...

Chuck

gsxr · #11 05-07-2003, 11:19 PM

Chuck,

My favorite alternate source (if FastLane can't get it) is Wholesale Parts - call Rusty at 800-741-5252, email rusty@mbz.org for a quote. Tell him Dave in Idaho sent ya.

If you have a green switch screwed into your receiver/drier, you will want to buy the newer red switch - it turns on the electric fans much sooner and helps cooling at low vehicle speeds. About $25, I think. You'll probably want a new drier if the system is opened anyway. Don't let it stay open while working on it, plug the hoses, etc immediately! The R-134a oils are horribly, horribly hygroscopic and create acids that will ruin your new compressor.

Since you have to replace the compressor anyway, flushing the evap & condenser (and lines) and swapping back to mineral oil makes a lot of sense. The compressor is the nasty part (IMO) to remove and drain/flush the oil out of. If you go to mineral oil, it's up to you what refrigerant to use, probably R-12 or AutoFrost are the 2 best choices (R-12 preferred).

If you stick with the PAG/POE oils, I'd skip R-134a and use something better like Duracool or AutoFrost's new R-134a replacements. I sure wouldn't charge back up with R-134a after the system has been evacuated & fixed...!

Good luck,

md21722 · #12 05-07-2003, 11:34 PM

If your compressor sufferred "black death" then flushing is your only recourse. Some parts don't flush well like condensers and may need to be replaced. Fastlane SHOULD carry that part. Just call Phil at the 800 number and ask. Sometimes it shows unavailable, but ALL parts are USUALLY available.

If you are using R134a again, if your system has not been directly opened to the environment and the compressor didn't throw black death all around, its probably okay to just add the necessary oil and refill, no flush, just replace the drier (anytime the system is opened - such as to change the compessor). Compressor vendors say warranty void if drier not replaced in many cases.

If you are going R12, then you'll need to flush everything including the evaporator, which will require replacement of the expansion valve (~$31). R12 is completely INCOMPATIBLE with the PAG/POE oils used with R134a. When the oil and genuine R12 mix, hydrocloric or hydrofloric acid will be formed and eat you system from the inside out. $$$. Flushing eliminates this problem.

The oil incompatiability is MOST severe with genuine R12. If you use something along the lines of Duracool or AutoFreeze, they claim to be much better able to deal with traces of previous refrigerants.

However, I recommend either R12 or R134a. The others are illegal in some states. Duracool is propane based and may contaminate R12 supply (bad!) if attempted to be recycled. AutoFreeze is SNAP approved IIRC and takes special AutoFreeze fittings (left hand).

One of your deciding factors will be what your buddy has equipment to deal with. If he's only got R134a then sounds like your decision is made. If he has both, make sure he flushes first.

HTH,

#13 05-08-2003, 08:13 AM

md21722,

What a great sermon! You are the MAN!

Have a great day,

CSchmidt · #14 05-09-2003, 10:17 PM

Folks,

It seems the compressor has siezed. I have searched and called a number of places. FYI - the Nippondenso compressor for the Mercedes I have (87 SDL) is used on many Chevy, Dodge, and Toyota applications. Of course the Mercedes version seems a bit more expensive. So far the ranges are going from $300 for a rebuilt to $750 for a new depending on place... so I'm still looking around a bit. My independent quoted "about $1000" for the whole job, hence my looking around.

The previous compressor was a 134 conversion, and it was in place for about 5 years and 100K miles, with a few leak / refill problems. It still had 134 in it, but must have run out of oil or just worn out. I'm leaning toward the $300 rebuilt, but need to consult with a few more places.

The other parts are coming together as well. I'm probably a week away from starting. I'll let you know what I find out and hopefully how it goes!

Chuck

leathermang · #15 05-09-2003, 10:28 PM

A couple of times lately mention has been made of changing the Thermostatic Expansion Valve..... ( actually a Combination valve on our cars )..... to one designed for 134a... but before I picked up my R12 I was asking about this... and could not find anyone that knew anything about a different one for 134a compared to R12 or that stocked one...
There are differences for orifice tube systems... and newer adjusting styles... but I never found anything about a " 134a expansion valve" ....
Does anyone have any hard info about this ? Sometimes they had one listed under" expansion valve 134a" but it always turned out to be the same part number as the one they had for R12....
Today I was standing holding the fuel nozzle at a local HEB gas station and was looking at the Coke vending machine from the back side... there was a sticker on the compressor which said "134a".... which surprised me because I thought R22 would have been standard on a non mobile system ....