Low "high" side, high "low" side, does that mean the compressor is bad? - PeachParts Mercedes-Benz Forum

pizzachef · #1 04-27-2009, 07:52 PM

I'm working on the a/c. The system had R-12 in it.
I removed the drier and exp valve. flushed the evap and the line to the drier. I couldn't get the bolt lose on the compressor or the fittings loose on the condenser so I didn't flush them. The a/c last worked about 2 years ago. The evap had green oil in it, and no visible debris came out, so I figured not flushing the compressor and condenser would be fine for now.

After flushing and reassembling, the system held a vacuum ~30 inHg for a few hours. I put in a 4oz can of ester oil and then a can of envirosafe (not under vacuum, like the can says). When I jumpered the compressor on, the low side went up to 80ish psi and the high side dropped almost to nothing. Stupidly, I tried a second can of envirosafe, and the low side went up over 100 psi and the high side dropped again. I shut the low side valve quickly so the can wouldn't rupture. When the car is shut off, the pressures equalize to about 100psi.

WTF? The compressor isn't seized, it can be spun by hand and the clutch engages and spins it. Why would the pressure increase on the wrong side? Should I start looking for compressors?

Thanks.

pizzachef · #2 04-27-2009, 08:37 PM

Quote:

Originally Posted by nhdoc

Clogged expansion valve, BTDT.

but its brand new and the pressures equalize when it shuts off...even so, clogged valve?
if that's the case, its easier/cheaper than a bad compressor, so i guess i'm glad to hear that. can i smack it with a hammer to free it up?

oh, and does the fact that the pressures change when the compressor is turned on mean that the compressor works?

thanks

pizzachef · #3 04-27-2009, 08:38 PM

uh oh, nhdoc's response disappeared...now it appears that i'm talking to myself

nhdoc · #4 04-27-2009, 08:40 PM

At first I misread your post and thought you had a clogged expansion valve but that would make the low side drop to near zero or even vacuum and the high side would spike. If the high side drops and the low side spikes up I would guess you have a clog elsewhere - I would suspect the receiver-drier (which you probably should have replaced anyway if the system hasn't been run in some time).

Where is the high side tap on your system? Is it between the condensor and R-D ? If so then it could be the condensor which has the clog.

Sorry I deleted the initial response to prevent confusion, but I guess I was too slow

Matt L · #5 04-27-2009, 09:00 PM

You checked again that you don't have the hoses reversed, right?

pizzachef · #6 04-27-2009, 09:09 PM

Quote:

Originally Posted by Matt L

You checked again that you don't have the hoses reversed, right?

I was hoping that at first...I did, they won't screw on to the incorrect ports, I checked

Here's a diagram...I'm not at the car right now, its dark outside, but I'm pretty sure the high pressure port is between 1 and 2, and the low pressure port is between 4 and 1.

Matt L · #7 04-27-2009, 09:28 PM

How about the connections at the compressor then?

I cannot fathom how a bad compressor would pull DOWN on the high side. Well, actually I can. If your high-pressure port is after the condenser or dryer (between 2 and 4) and the condenser/dryer is plugged, then the high-side would pull down. But so would the low side.

pizzachef · #8 04-27-2009, 09:39 PM

I didn't touch the compressor connections. Well, actually I did, I tried to loosen the bolt holding the two lines on but I couldn't make it budge. So that connection remained unchanged. It was good 2 years ago.

Matt L · #9 04-27-2009, 09:48 PM

I still can't think of anything that could possibly cause the low side to go up and the high side to go down at the same time. Both going up or both going down, I could understand.

Compressors don't fail by pumping the wrong way (unless we're talking about AC-powered scroll compressors, and then pumping the wrong way that causes failure).

TOPGUN · #10 04-27-2009, 10:29 PM

This is a far reach for an answer. An R-12 system would have had 1/4 flare fittings. The R-134 adapters will fit on either high or low side 1/4 flare fittings. The R-134 adapter for the low side suction line should be connected to the left hand side blue gage. The R-134 adapter for the high pressure side should be connected to the right hand red gage. The larger fitting of the two should be installed on the high side. (Usually after the condensor but before the reciever dryer. If the fittings were reversed your problem could be duplicated provided there is a blockage on the high side.(dryer plugged or txv not opening). If you have good equipment and experience disregard this post.So far Matt L has the best answer.

leathermang · #11 04-27-2009, 10:56 PM

Here is an important part of the rules ... since you now have a blend in your system...

"refrigerant, the technician must first extract the CFC-12, must cover the CFC-12 label with a label that indicates the new refrigerant in the system and other information, and must affix new fittings unique to that refrigerant."

I have seen a chart at one time with the specs on the different fittings for this but have not been able to find it yet this evening...
You do not want to mess up someone's expensive machine... or violate EPA rules ..but not putting the proper information and fittings on your AC system.

The rules concerning Blends...
from http://www.epa.gov/ozone/title6/609/justfax.html

Using Older Equipment to Recover Blends

Technicians have a number of choices in recovering blend refrigerants. One option is that a technician may permanently dedicate an older piece of equipment he owns to recovering one or more blend refrigerants. The technician may also use this equipment to recover contaminated CFC-12 and HFC-134a and other "mystery mixtures." This equipment, however, may no longer be used to recover uncontaminated CFC-12 or HFC-134a. Refrigerant recovered using this kind of "junk" tank must then be shipped off-site for reclamation or destruction.
Using New Equipment to Recover Blends

Another option for recovering a blend refrigerant is to use a new piece of EPA-approved equipment designed to recover, but not recycle, any single, specific blend refrigerant. The EPA regulation published in December 1997 includes an appendix that describes the standards that this new equipment must meet.

In addition, EPA is currently working with independent testing laboratories and equipment manufacturers to devise a standard for new equipment that can recover, but not recycle, both multiple blend refrigerants and contaminated CFC-12 and HFC-134a. EPA will finalize a standard for this type of equipment by the end of 1998. This equipment may be commercially available by the 1998 A/C season. EPA expects to grandfather any equipment purchased in 1998 before the EPA standard becomes finalized.
Recycling Blends

As of June 1, 1998, EPA allows recycling of refrigerant blends used in motor vehicle air conditioning systems (MVACs), provided that a) recycling equipment meets a new Underwriters Laboratories (UL) standard (Standard 2964) and b) refrigerant is returned to the vehicle from which it was removed. The only exception to item b) is for fleets of vehicles with a common owner; recycled blend refrigerant may be moved among vehicles within such a fleet. EPA detailed this policy in a June 1, 1998, open letter to the industry. Certified recycling equipment may be commercially available during the 1998 A/C season. EPA plans to adopt this new UL standard into EPA's regulations and to grandfather any equipment that (1) meets the UL standard and (2) is purchased before the date on which EPA publishes a proposed rule to adopt the UL standard.
Converting CFC-12 or HFC-134a Recover/Recycle Equipment for Use with Blend Substitutes

EPA currently prohibits the conversion of existing CFC-12 or HFC-134a recycling equipment for either temporary or permanent use with a blend refrigerant, unless the equipment is used only to recover, but not to recycle, the refrigerant. In the future, EPA may issue regulations allowing these conversions but placing certain restrictions on who performs the conversions, what models may be converted, etc.
Technician Training and Certification

Technicians who repair or service MVACs that use blend refrigerants must be trained and certified by an EPA-approved organization. If a technician is already trained and certified to handle CFC-12 or HFC-134a, he does not need to be recertified to handle a blend refrigerant.
Recordkeeping Requirements

Service facilities that work on vehicles that use blend substitutes must certify to EPA that they own approved equipment designed to service these refrigerants. Note that this certification is a one-time requirement, so that if a shop purchased a piece of CFC-12 or HFC-134a recycling equipment in the past, and sent the certification to EPA, the shop does not need to send a second certification to EPA when it purchases a second piece of equipment, no matter what refrigerant that equipment is designed to handle. If refrigerant is recovered and sent to a reclamation facility, the shop must retain the name and address of that reclaimer.
Sales Restrictions

Section 608 regulations prohibit the sale of any size container of any blend refrigerant to anyone other than a certified technician. This prohibition began in November, 1994.
Retrofitting Vehicles to Alternative Refrigerants
Although Section 609 of the Act does not govern retrofitting, Section 612 of the Act, which describes the Agency's Significant New Alternatives Policy (SNAP) program, does require that when retrofitting a CFC-12 vehicle for use with another refrigerant, the technician must first extract the CFC-12, must cover the CFC-12 label with a label that indicates the new refrigerant in the system and other information, and must affix new fittings unique to that refrigerant. In addition, if a technician is retrofitting a vehicle to a refrigerant that contains R-22, the technician must ensure that only barrier hoses are used in the A/C system. Finally, if the system includes a pressure relief device, the technician must install a high-pressure compressor shutoff switch to prevent the compressor from increasing pressure until the refrigerant is vented.

Much more information about the SNAP program and about retrofitting procedures is available in a fact sheet called Choosing and Using Alternative Refrigerants.

JimmyL · #12 04-27-2009, 11:17 PM

Quote:

Originally Posted by leathermang

Here is an important part of the rules ... since you now have a blend in your system...

.....................

Remember, he's just trying to figure out what is wrong, not what the labeling rules are.

So far the high and low side fittings being reversed seems to be the most plausible. I had a problem of the readings being very similar to each other and I believe that was a clogged exp. valve.

BTW, we're guessing this is on the TD, but you didn't really mention. If it's the TD, being a Euro often means a different compressor and AC line routing. The low side port or Federal W123's is usually right in the upper front of the engine and the high side is down kind of behind and under the alternator.

Hmmm, your diagram above makes it look like the 240 with the York compressor. If so I have no idea where those fittings are.....

pizzachef · #13 04-27-2009, 11:26 PM

Quote:

Originally Posted by leathermang

..must cover the CFC-12 label with a label that indicates the new refrigerant in the system and other information...

done

Quote:

Originally Posted by leathermang

...and must affix new fittings unique to that refrigerant."

the low side fitting i got from envirosafe fits on the car's low side port, but the high side fitting that I got from them does not. I'm not sure what's up yet, for now I'm using the stock r-12 fittings.

Don't worry, I'm not out to ruin anyone's reclamation machine or their stock of r-12.

Quote:

Originally Posted by TOPGUN

This is a far reach for an answer. An R-12 system would have had 1/4 flare fittings. The R-134 adapters will fit on either high or low side 1/4 flare fittings. The R-134 adapter for the low side suction line should be connected to the left hand side blue gage. The R-134 adapter for the high pressure side should be connected to the right hand red gage. The larger fitting of the two should be installed on the high side. (Usually after the condensor but before the reciever dryer. If the fittings were reversed your problem could be duplicated provided there is a blockage on the high side.(dryer plugged or txv not opening). If you have good equipment and experience disregard this post.So far Matt L has the best answer.

I got two fittings with my refrigerant, along with new stickers. The high pressure port fitting (red cap) doesn't fit on the car's high pressure port. The low side fitting (blue cap) does fit, but for now I'm just using the car's stock screw-on ports. The port that's right on top in the engine bay is the high pressure port...its on a line between the compressor and the condenser (if I'm wrong, please tell me). The low pressure port is under the car, on a line between the evaporator and the compressor (again, if I'm wrong, please tell me). So the blue hose goes under the car, the red hose goes to the port on top. Tomorrow I'll look at the car again and make for certain that I don't have everything backwards...if I do, then I have a lot to learn

JimmyL · #14 04-27-2009, 11:34 PM

Quote:

Originally Posted by pizzachef

The port that's right on top in the engine bay is the high pressure port...its on a line between the compressor and the condenser (if I'm wrong, please tell me). The low pressure port is under the car, on a line between the evaporator and the compressor (again, if I'm wrong, please tell me). So the blue hose goes under the car, the red hose goes to the port on top. Tomorrow I'll look at the car again and make for certain that I don't have everything backwards...if I do, then I have a lot to learn

OK, still don't know what car, but on most W123's, you have it bass-ackwards......

leathermang · #15 04-27-2009, 11:36 PM

Typically high pressure side lines will be smaller than the low pressure lines....

I am glad that you are following as many of the rules as the items they sent you will allow..