A/C recommendations for the MB vehicles - Page 12 - PeachParts Mercedes-Benz Forum

vstech · #**166** 08-07-2011, 08:15 AM

ok
official charging method with a tank.
FULLY evacuated system. lines from charging manifold to car attached, and closed.
tank inverted for liquid dispersal, and valve open, tank resting on digital charging scale. preferably with an exact weight alarm, or a digitally controlled charging valve.
car and system OFF.
open the HIGH SIDE VALVE and add in 90% of indicated weight, close high side manifold valve, turn can back to gas discharge side up, then start the system. finish the charging with gas until the correct weight of refrigerant is indicated by the scale.

Matt L · #**167** 08-08-2011, 01:42 PM

Hopefully this link will remain active for a bit:

http://www.sears.com/shc/s/p_10153_12605_00916236000P?sid=IDx20070921x00003a&ci_src=14110944&ci_sku=00916236000P

Are these sorts of units sufficient for producing dry air for purging? I expect that they're made for painting.

vstech · #**168** 08-08-2011, 02:35 PM

no.
it's also unlikely they are voluminous enough for painting. more likely they are for running either control air for commercial a/c controls, or for pneumatic operation of equipment like benders and brakes in a shop of some sort.

leathermang · #**169** 08-11-2011, 03:21 PM

http://www.youtube.com/watch?v=HztDhgyq6wc&feature=related

Nice explanations, graphics .... note they had the blower on high instead of low for the function test... otherwise good material...as far as I watched it... two others go with it....

leathermang · #**170** 08-16-2011, 03:26 PM

http://www.hemmings.com/hmn/stories/2009/11/01/hmn_feature30.html

leathermang · #**171** 08-23-2011, 12:22 AM

http://www.youtube.com/watch?v=_6Qlob80iE8&feature=related

sjh · #**172** 08-23-2011, 01:06 AM

Quote:

Originally Posted by leathermang

http://www.youtube.com/watch?v=_6Qlob80iE8&feature=related

Thanks.

In my world the 'saturation point' is a phase change and the P-T relationship of this 'change of state' is plotted on a phase diagram.

I'm pretty sure you'll know that but I needed to translate the terms for myself to better understand the video.

vstech · #**173** 08-23-2011, 08:49 AM

in my world, saturation point is a temp reading you will get at a given pressure without any heat added.

that's all.

there is a lot of scientific info you can infer from the saturation point, but what is important is the actual pressure, and the actual temperature. when charging a system with a txv, like all our cars (except 1980SD's car) the temp of the liquid line exiting the condenser is crucial to understanding the amount of charge in the car. the only problem, is there is no where to measure the actual pressure of the line. so for our cars, we have to measure the suction pressure and temp to get a close ballpark for the charge.
this is why it's important to weigh in the correct charge. "adding" refrigerant to our systems is problematic.

sjh · #**174** 08-23-2011, 10:48 AM

Right.

So on the above graph it is along the blue line. A phase change occurs. Either liq -> gas or vice-versa. It's the phenom where the working fluid either absorbs or releases the greatest amount heat.

I'm still working on understanding the terms you use, relating them to words/concepts a physicist/physical chemist would use.

I'm assuming high T gas enters the heat exchanger before the radiator. I think it's called the condenser. Here the gas turns into liq, the point at which that occurs being the saturation point. That is the temp at which it turns into a liq depending on the gas P in the condenser.

Continuing on at some point the cooled liq expands to cool the car. I'm thinking this may be metered and takes place within an expansion chamber. It's possible metering takes place before entering the compressor. I don't know I'm getting my handle on the physics. I need to learn that first and then I 'll learn your terms.

Anyway the process in the expansion chamber, where I'm thinking liq -> gas, the T at which that occurs depends on the P at that point and is also a saturation point. Which would be found on the blue line on the phase diagram.

I'm speculating in my comments. Please correct where I'm wrong & since this is a sticky alter, delete as best. If this is the wrong thread to be asking these questions I'll do it in a different area.
.

1980sd · #**175** 08-28-2011, 08:51 PM

Quote:

Originally Posted by vstech

like all our cars (except 1980SD's car)

It's ready for vacuum and charge

leathermang · #**176** 09-03-2011, 01:21 PM

I love the clips from this movie anyway.... all of life seems to relate to it now...but this is interesting video...I currently have a 2001 Lincoln Towncar the blower works sometimes if it wants to... if I disconnect the battery it will sometimes reset that circuit board... not always...we are about to get out of 100 plus temperatures this next week... maybe I can get motivated to change out that board... or hard wire the blower ( AC works fine..only the blower not working )...and my 95 Lincoln is intermittent also... sometimes just fine.. other times randomly barely cool...

http://www.youtube.com/watch?v=ah4OEeCu1KE

1980sd · #**177** 09-04-2011, 10:54 AM

Quote:

Originally Posted by leathermang

I love the clips from this movie anyway.... all of life seems to relate to it now...but this is interesting video...I currently have a 2001 Lincoln Towncar the blower works sometimes if it wants to... if I disconnect the battery it will sometimes reset that circuit board... not always...we are about to get out of 100 plus temperatures this next week... maybe I can get motivated to change out that board... or hard wire the blower ( AC works fine..only the blower not working )...and my 95 Lincoln is intermittent also... sometimes just fine.. other times randomly barely cool...

http://www.youtube.com/watch?v=ah4OEeCu1KE

He forgot one thing. LOW PRESSURE SWITCH! I wouldn't put straight power to my compressor without one... Seems like you could lock that sucker up quick if it had a low charge!

Good video, bad info.

leathermang · #**178** 09-04-2011, 11:08 PM

Always flush the line when hooking up with some refrigerant to get rid of the air in it....just a little bit... harder with the new fittings but can be done... may can use the manifold holder fittings to do that...

dieseldan44 · #**179** 10-14-2011, 08:28 AM

OK, I read through the entire thread.

vstech and leathermang - I'll make you guys a deal - if you help me through my A/C 'rebuild' I'll document it all and write it up so it summarizes this thread into an article and DIY with FAQ's. You guys are warriors answering the same q's every year, so I want to make it easier for everyone in the future.

Normally, being in Boston, AC is not high on my list, but I have gotten so frustrated with no shops around here knowing what do on any A/C system, Id rather just buy the gear and do it myself.

I am rebuilding the 82 300D's AC. It is my fiances car and I want to hear complaints on how cold it is

- It had been converted to 134, but I would like to deconvert it to R12
- new evaporator already installed
- new condenser to be installed
- new compressor and o-ring kit from Carlisle in SA, TX is sitting at my feet
- new R/D purchased
- new expansion valve installed
- new upper manifold A/C hose. I'd like to re-use the lower manifold if possible.

tools i have acquired:
- robinair 2 stage 1.5 CFM vacuum pump
- R12 and R134a gauges
- A/C leak detector

I plan to in this order:

this fall:
- flush entire system and blow clean with dry shop air
- replace all o-rings using nylog sealant
- add 4 oz of mineral oil to compressor, 2 oz to evaporator, 2 oz to R/D
- pull vacuum for hours
- charge with 4 oz of R22 and inert gas (*) to check for leaks
next spring (car sleeps while salt is on road):
- re-evacuate, replace R/D, hold for an hour, then charge system with propane (j/k...seeing if you guys read this far) R12.

Questions for the experts -

(*) 1.) Can I use MIG welding gas (75% argon, 25% CO2) as my inert gas for the pressure test? I ask because I already have plenty of it.

2.) For the deconversion, I need to go back to R-12 fittings. How can I tell if I have damaged anything by taking the 134a fittings off? That isn't entirely clear.

3.) For the blowing out of the lines with air after the flush. If I use my air compressor with an inline desiccant and oil/water separator - is that OK? Even if there is a tiny amount of moisture that gets through, won't that boiled out during the vacuum step? (I could use welding gas here, but I don't want to waste it)

thanks, looking forward to learning to do this the right way...
dd

ROLLGUY · #**180** 10-14-2011, 10:21 AM

Quote:

Originally Posted by dieseldan44

Questions for the experts -

(*) 1.) Can I use MIG welding gas (75% argon, 25% CO2) as my inert gas for the pressure test? I ask because I already have plenty of it.

2.) For the deconversion, I need to go back to R-12 fittings. How can I tell if I have damaged anything by taking the 134a fittings off? That isn't entirely clear.

3.) For the blowing out of the lines with air after the flush. If I use my air compressor with an inline desiccant and oil/water separator - is that OK? Even if there is a tiny amount of moisture that gets through, won't that boiled out during the vacuum step? (I could use welding gas here, but I don't want to waste it)

thanks, looking forward to learning to do this the right way...
dd

Great questions for the experts, and I have been wanting answers to similar questions as well. Especially about the MIG gas. I have plenty as well, and was wondering if it would be a decent substitute for other dry gasses that are suggested.