A/C recommendations for the MB vehicles - Page 11 - PeachParts Mercedes-Benz Forum

leathermang · #**151** 07-12-2011, 08:41 PM

I would use a standard flushing fluid myself to make sure I avoided any residue which might cause problems later...
The MB AC manual is very specific about the whole procedure.. even specifying which direction to run the fluid through the disconnected hoses....

gskurka · #**152** 07-12-2011, 10:42 PM

Is the MB flush procedure available on this site somewhere?

remotemark · #**153** 07-16-2011, 06:34 PM

Did the reverse conversion. Forty degree vents today with 85-90 ambient. I'm pretty happy! If I could figure out how to degrime evap fins, i'd probably be even happier.

Quote:

Originally Posted by remotemark

I'm sick of the crappy cooling I get from the 134 in my 84 W123 300D. In the shade or on a cool morning, I can get 55-60 degree air from the vents, but when it's hot here in Charm City, I'm lucky to get mid-70s, and when 95 and the muggies hit, it doesn't seem to do much of anything. So I've decided to bite the bullet and do a proper reverse conversion to R12.

I bought some 12 oz. cans of R12 off a fellow on CL ($100 for 16 cans). I've ordered a new R4 compressor, a new condenser (mine has plenty o' bent fins -- maybe 40-50% of them), a new receiver-dryer, and a new high-low switch. Does anything else need replacing to do this right? Any of the hoses?

I've found a good radiator and a/c shop and will ask them to do the following for me: 1. get out the 134. 2. hook up the hoses to their flushing rig and flush all of the oil out of the hoses and the evaporator as many times as they can. 3. install the new components. 4. pull a vacuum to see if there are any leaks. 5. charge with oil and R12 (I have to supply it for them).

Have I covered all my bases? What is the correct R12 charge for my car?

Thanks!

leathermang · #**154** 07-16-2011, 06:48 PM

Congratulations.... really glad to hear that...
I have been reading in the MB service manual trying to figure out how to access the evaporator..

gskurka · #**155** 07-22-2011, 11:19 PM

With the a/c set at the coldest setting and blower speed on high, occasionally the blower will stop for a few seconds and then restart. I have been putting the fan on the low setting when this happens. I checked the strip fuse and tightened the mounting screws. Any thoughts on what might be causing this?

FWIW: With 100 degree temperatures in NJ today, I'm getting a delta t of about 30 degrees F at the middle vent with recirculation on; PO converted to 134a. With these extreme temperatures, I'm seriously thinking about going back to R12.

Greg

vstech · #**156** 07-22-2011, 11:29 PM

it stops on high? odd. bearings would be my guess... as in high, the resistor pack is out of the circuit. your fuse is the original or the upgraded strip fuse on the fender? 91 should be on the fender, and the 30 amp strip fuse may be cracked... pull it and look it over carefully.

leathermang · #**157** 07-23-2011, 12:00 AM

Greg... to put that Delta T into perspective.... a room AC only expects to provide 6-8 degrees difference....
It may not be providing all the cooling you want or need...but it is doing a lot of work in these record temps and high humidity....

gskurka · #**158** 07-23-2011, 11:28 AM

Thanks for the input guys.

The strip fuse is located at the firewall. The holder looks like it has been overheated a few times (partial melting of the plastic). Is there an upgrade available? In the meantime, I'll put in a new strip fuse. The one that's in there I replaced about 3 years ago and it looks a bit oxidized, but the contacts seem to be secure.

colincoon · #**159** 07-23-2011, 11:44 AM

I recently found a tank of R12 in my grandpas garage (a TANK!) and will be putting it in my newly rebuilt AC system. My question is how do I measure the 2.6 pounds required to fill the system when using the tank? Is it as easy as putting it on a scale and watching it's weight drop or a little more difficult than that?

leathermang · #**160** 07-23-2011, 12:25 PM

Yes. that is the method... but it needs to be an accurate scale...

vstech · #**161** 07-23-2011, 03:15 PM

a UPS digital scale can do it, We professionals use refrigerant digital scales.

gskurka · #**162** 07-23-2011, 04:50 PM

Quote:

Originally Posted by vstech

it stops on high? odd. bearings would be my guess... as in high, the resistor pack is out of the circuit. your fuse is the original or the upgraded strip fuse on the fender? 91 should be on the fender, and the 30 amp strip fuse may be cracked... pull it and look it over carefully.

On a short trip this afternoon, the a/c was working fine; blower on max. I shut the vehicle down for a few minutes without pressing "0" to shut off the a/c. Upon restart, no blower, but the compressor clutch is engaging. I checked the strip fuse (ok) and changed #5 fuse in the box next to the brake booster as a precaution. I think I found the blower motor on the passenger side of the vehicle behind an interior trim panel and a Behr cover with an aluminum heat exchanger mounted to it. I pulled the red and blue wires off of the motor and attached a trouble light. The light illuminates with the fan controls. My next check will be to apply 12v to the motor directly. Assuming it doesn't run, how do I remove the blower motor? Can someone provide direction here? John mentioned bearings above. Are the bearings serviceable or do I just replace the motor? Vehicle is a '91 350 SD.

Thanks in advance.

Greg

vstech · #**163** 07-31-2011, 11:37 AM

I moved the conversation to it's own thread.
http://www.peachparts.com/shopforum/showthread.php?t=302705

colincoon · #**164** 08-07-2011, 01:00 AM

Another question about filling with a tank...

Is there any special trick to it? On my tank it has an arrow pointing up that says "gas" and another pointing down that says "liquid" in terms of how you want the stuff to go in to the system. I know that with cans you are supposed to rock the can side to side to get it all in, but from what I've said not with a tank.

I'm assuming that I just let the tank sit on it's own and not touch it, the liquid will turn to gas anyway, but I wanted to double check before I accidentally waste some precious R12.

Matt L · #**165** 08-07-2011, 01:17 AM

Liquid in the low-side line can slug the compressor. You only charge with liquid with the compressor off. If you are charging from the low-side line with the compressor running, it's gas only.

Liquid doesn't turn to gas on its own. It takes heat.