Can you just use O-rings from a hardware store? - Page 2 - PeachParts Mercedes-Benz Forum

lietuviai · #16 09-17-2007, 11:35 PM

I was planning on maintaining the old R12 system since the outcome will be more predictable. Good advice Frank.

tangofox007 · #17 09-18-2007, 08:00 AM

Quote:

Originally Posted by lietuviai

I was planning on maintaining the old R12 system since the outcome will be more predictable.

There is not much that is unpredictable about an R-134a conversion. The outcome is very predictable; marginal a/c performance is assured!!!

FRANKNBENZ · #18 09-18-2007, 03:39 PM

DJ,

TF007's recommendation is right on. The folks at Arizona Mobile Air (ACKITS.COM) are pros, knowledgeable, and sell great stuff at the most reasonable prices I've Googled or BizRated.

On this and other forums there is a lot of good guidance on DIY AC maintenance and repair. Please avail yourself of this great body of knowledge. The point I guess I am trying to make is this: If you are going to go through all the hassle of O-ring changeout, it might be a good time to R/R the major compontents and do preventive maintenance.

You don't give any indication of your level of AC DIY, and I'm still learning every day, but here are some of my homework notes and thoughts you might mull over:
+ Cars pre-1994 such as my older MB's were designed to run R-12.
+ Most older US model MB's have GM-style R-4 rotary compressors. These apparently come in two manifold types, flat and stepped. Clearly the seals needed at this location must match the type.
+ Some folks say nix on the R-4, that those from Hodyon (Hancock Industries) are better.
+ I got my R/D and XValve from either Fastlane or ***************, both good suppliers.
+ Study for and take the 609 certification test online. That gets you the legal ticket to buy R-12.
+ Best advice I've read: when tuning up the AC:
- ID the four zones in a mobile AC system and inspect each, by component, for road damage, wear (chafing), and leaks.
- Professionally recover the refrigerant. You can do it DIY but the gear is about $1,000 per refrigerant type.
- Break open all the fitting lines and inspect O-rings. I use one of those small, segmented plastic boxes (like an egg crate), label and insert for later measurement and reference when buying replacements.
- Remove, inspect, note numbers, dimensions, and maybe photograph the compressor, receiver/drier, and expansion valve. Do not discard until the new replacement items come in (about $250). Stuff should match.
- Do a zone and component system flush generally along the lines of that shown in Diesel Giant's pictorial. He uses aerosol canned flush; I prefer liquid in a $40 flush gun operated by shop air.
- Note his recommended lube. This magic potion goes into the compressor, the receiver/drier, and the O-rings get dipped in it prior to component fitting assembly.
- Reassemble with a friend, especially mounting the new compressor -- unless you're a masochist. Torque fittings to, but not over, spec.
- Evacuate to 29"Hg for an hour. You can rent a 4hp vac from Autozone or buy one online, about $250-$350.
- If you have it, do the nitrogen thing to get all the H2O out.
- Charge by weight -- the best -- or by gauge -- less reliable in older systems. Do not overcharge.

And, after all this is over, if, on a 90 degree ambient high humidity day, you don't get 36 degrees at the vent

...or less, start doing push-ups...

Good luck.

lietuviai · #19 09-18-2007, 10:28 PM

Awesome advice Frank. I really appreciate the time you took to guide me through properly refurbishing my A/C system. I would certainly have left a few things out or would have tried to short cut others without reading your post.
I have had some A/C experience professionally but I haven't done any major work in nearly 20 years. The last job was a transplant of a complete system from an A/C equipped car to a non-A/C equipped car. I left the evacuation and recharge to a friend who owned a shop. AFAIK the system is still operating on the same charge in that car to this day.