A/C Refurb Questions - Page 2 - PeachParts Mercedes-Benz Forum

jcyuhn · #16 04-22-2004, 04:56 PM

They're both basically OK, both Yellow Jacket and Mastercool are good brands.

The Mastercool set looks like the same setup I have. One significant comment - it's not really R12 ready. Those smaller bits in the picture are the R134 adaptors - they screw into the end of the hoses. Although the threads on the hoses match R-12, the hoses do not have shut-off valves to retain refrigerant (as required by federal law), nor do they have effective depressors for the valve core in the schraeder valve. (Does that part have name?)

I ended up picking up a nice set of R-12 shut-off adapters which screw into the hoses in the same way as the R-134 adapters shown. Cost was about ten bucks each - think I sourced them at the local Graingers, a big contractor supply chain. Try http://www.grainger.com and check out SKU numbers 3KU71 and 3KU70. Look under tools and then manifold guage set accessories. These work great on my 124, which likes one straight connector and one 90 degree connector.

I don't share Larry's deep concerns with mixing R-12 and R-134a. A few molecules of R-12 in a 134 system (or vice-versa) won't cause any problems. I'd be more concerned about mixing oils. The manifold hoses do eventually get some refrigerant oil in them. The PAG oil used in 134 factory systems doesn't like chlorinated refrigerants (i.e. R-12) very well. I don't think getting a trace amount of mineral oil in a 134 system is any big deal. I personally only use more expensive synthetic refrigerant oils in my vehicles; these oils work in both 12 and 134 systems, so mixing doesn't matter.

My wordy $.02

- JimY

#17 04-22-2004, 05:24 PM

I would get the less expensive set. It will serve you just fine.

The EPA Test can be taken for $15.00 at www.imaca.org

You are wise for buying R12 gauges for R12 and R134 gauges for R134. Mixing the refrigerant itself is not really a problem, but you should try not to mix the oils. Mineral oil works great in R12 systems and is cheap. That way your R12 gauges will never see anything except 12 and mineral oil and you R12 systems will have no doubt of being contaminated in any way except the possibility of moisture if you don't evacuate properly.

Good luck,

jbhebert · #18 04-23-2004, 10:15 AM

Thanks for the new link... the one at epatest.com has been down for 2 days.

Anyways, I just finished the test and printed out my temporary certificate. Time to buy some tools!

jbhebert · #19 04-23-2004, 11:45 AM

Think I should pick this up while I'm at it?

http://www.acsource.com/index.asp?PageAction=VIEWPROD&ProdID=371

Seems like a good deal for the complete package. Lets me do other fluids, too.

#20 04-23-2004, 12:23 PM

I have one of these that I bought without the lamp and the other than a/c items. It works well. It can also be refilled when empty by turning the handle back out counterclockwise and then blowing back the piston with air and filling it with a dye solution that I got from my local auto a/c house.

This is a very good price for the injector AND the light.

Have a great day,

Eric Eliel · #21 04-23-2004, 12:27 PM

I think they use that on CSI looking for......................opps (family board) :-)

jbhebert · #22 05-12-2004, 09:23 AM

OK, so I got my gauges and leak detector kit. I also got the Mastercool manual, which has a lot of good info. However, in the Servicing section where it talks about hooking up the gauges, it says:

"After the test gauges are attaced it will be necessary to purge the test hoses of all air before proceeding with testing. Use instructions, provided with the recycling machine, to properly purge the test hoses."

Does this mean that I have to get a recycling machine or pump, even if I just want to check pressure and/or add refrigerant? Is there another way to purge the air?

Thanks again.

126nut · #23 05-12-2004, 10:06 AM

That's where it gets tricky.

A mobile refrigeration certification is laughably easy to get but in most areas, city and state codes, to be 100% in compliance you will also need a recovery machine and some fashion of leak detection equipment. They, recovery machines, are getting cheaper but the last one I bought, for commercial building use, was almost 2 grand. A vacuum pump is also another necessary tool, nitrogen cylinders and manifold set is helpful as well.

There is a reason most shops charge the bucks for A/C work, lots of fancy and expensive equipment is required.

zafarhayatkhan · #24 05-12-2004, 12:33 PM

If the system has leaked over a period of 10-15 years, how can one determine how much oil to add?

What are the consequences of too much oil in the system?

jbaj007 · #25 05-12-2004, 12:52 PM

J.B. Hebert,

"Is there another way to purge the air?"

This is ONLY for historical perspective; but in the "old" days, you would just loosen the hose at the gauge and run a tiny bit of refrigerant thru for a second, to purge air. Patently illegal, now, but common and efficient in the past.

jbhebert · #26 05-12-2004, 04:27 PM

jbaj007 -

Thanks for the info... I would of course never think of doing that now...

In all seriousness, should I start looking for a vacuum pump, or is it not worth it for what I'm looking to do? I just want to be able to check/add refridgerant.

Thanks again.

#27 05-12-2004, 04:39 PM

If you do much auto a/c work, it is inevitable that you will have to repair a leak somewhere in an empty system. That means breaking apart the system, replacing the o-ring, the hose, the compressor, the evaporator or whatever is leaking. Any time you OPEN the system you MUST evacuate before recharging. Otherwise the moisture left behind will not only prevent the system from cooling properly but will also combine with the refrigerant to make an acid that will eat its way through aluminum components from the inside out.

Since you don't currently have a situation needing evacuation, take your time and try to find a bargain on a vacuum pump.

Good luck,

jimandsuzy · #28 05-12-2004, 10:08 PM

Years ago a friend made a vacuum pump by hooking up an old auto a/c compressor to an electric motor by way of a V belt on a piece of plywood. The vacuum was the low pressure inlet side of the compressor. It pulled 30" of vacuum in just a couple of minutes. 2 years ago I borrowed a small air compressor and put an A/C fitting on the inlet side where the air filter was screwed in with a pipe thread fitting and it pulled over 29" vacuum in about 5 minutes. I did this to change my Sidekick from R12 to R134. It's worked fine so far. Point being that you may be able to get a used small compressor cheaper than a vacuum pump or get a used auto A/C compressor and electric motor for cheap. For what it's worth.

#29 05-12-2004, 11:06 PM

Hello All:

First great thread, good info and nice dialog. I have a question, I have a 93,190E, 2.6 liter that has been converted to R134. I have been thinking of converting back to R12. Your discussion concerning the lub for the system is interesting.

My question to the forum: is the oil for a R134 system compatable with a R12 system?

It appears that the R12 oil is not compatable with R134 system.

What would be required to convert back, because its just not working down here in Florida.

Thanks,

jbhebert · #30 05-13-2004, 08:35 AM

The oils are definately not compatible. R-13a uses PAG (Polyalkylene Glycol) or ester oil. R-12 uses a mineral based oil. I think in your case you would have to evacuate and flush the entire system before reintroducing R-12 in it. But I'm sure others on the list much more knowledable than I can give you more details.

Good luck.