AC Minor Overall, Tool Questions to do it Right! - PeachParts Mercedes-Benz Forum

veggie190 · #1 06-04-2007, 11:58 PM

Well, I do a lot of driving and I know summer temps are about to soar…time to get that AC working!

I have done my “homework” reading several AC threads. My main questions are about the tools to get the job done. Here’s what I’ve bought so far:

Receiver/Drier
Expansion Valve
AC High/Low Switch
AC/Refrigerant Temp Sensor
Freeze 12 (in the process of buying)

I bought the car last October so I have not driven it in hot tempatures. So far on sunny days in the mid 70’s the vents produce cool air, but not cold…definitely more comfortable to have the windows open.

Steps to complete the minor overhaul (as I understand it):

1. evacuate the system
2. replace expansion valve and o rings
3. add 5 ounces of pag oil to drier
4. install drier with new switch, sensor, and o rings
5. pull vacuum for approximately 45 minutes
6. stop, wait 15 minutes see if vacuum holds
7. if doesn’t find leak and fix
8. when vacuum holds connect AC gauges and put 2 pounds of Freeze 12 in

Any holes in the game plan…I believe I have the gist.

Where do you get a vacuum pump and refridgerant gauges? I’ve asked at three auto stores and I haven't found someone who rents them. Next option is to buy, what gauges and pump will work?

Will these 134a guages that are on sale work?
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=92649

Do I have to buy a R12 set like this? What’s the difference?
http://www.fm-distributing.com/catalog_i1528059.html?catId=68133

I this a good pump? I don’t want to break the bank but want something that will do the job.

http://cgi.ebay.com/ebaymotors/FJC-2-5-CFM-Vacuum-Pump-Air-conditioning-A-C-R12-R134_W0QQcmdZViewItemQQcategoryZ63700QQihZ011QQitemZ320121119355QQrdZ1QQsspagenameZWDVW

And last, any recommendations on top vs side can tap?

Thanks a lot for the advice. I am really looking forward to a COOL ride!

Matt L · #2 06-05-2007, 12:06 AM

You might be able to rent the pump from Auto-Zone or similar and save some money on a seldom-used tool (what if it corrodes inside from lack of use?).

However, I would recommend using R-12 or R-134a and not any blends. These can be trouble in the long run, and you can still buy R-12. The price difference of the refrigerant itself is so little that it shouldn't be a factor in your decision.

vstech · #3 06-05-2007, 12:09 AM

the HF set will do both 12 and 134a. you don't even need to install 134 fittings on your car if you use that set. and if you are using freeze 12, you really don't want to install 134 fittings. LABEL the CAR stating you have a blend refrigerant FREEZE 12! you don't want the next driver who gets your car ( it could be your kid!) to have a tech put in the wrong chemical.
that pump is just fine for a car.
BUT it is improper to check for leaks with the pump... you want to pressurize the system with a small amount of gas, not liquid. build it up to 30 psi and then wait 24 hours. check the pressure, if it has not dropped, you are leak free.
checking with a vacuum, causes the system to draw in moisture, if there are leaks.
John

veggie190 · #4 06-05-2007, 07:05 PM

Oh, great to know that the HF set can be used with Freeze 12. I had read it operates at a "lower pressure" so 134 gauges cannot be used with R12.

So you pressurize the system with gas to check for leaks. What kind of gas/how do you do that? Should I replace my expansion valve and drier and then pressurize with gas?

Thanks a ton for the advice.

Kuhlrover · #5 06-05-2007, 11:44 PM

After replacing all the components you list, you will want to vacuum the system to remove any moisture and air that you allowed into the system. After you vacuum the system you can use a small amount of refridgerant or use nitrogen into the system to bring it up 30 to 70 lbs. Take note of what the temperature is inside the car and outside the car. When you check the pressure the next day, the temperature should be the same and so should the pressure.

This should identify any medium sized leaks. Large leaks can be detected using a soap water solution. As the gas escapes it forms bubbles. Very large leaks you should be able to hear. The very small leaks are the hard ones to find. I have seen old A/C hose that will weep R-134a through the side wall of the hose.

TimK

TimK

JimmyL · #6 06-06-2007, 01:24 AM

I tried 2 different sets of Harbor Freight gauges, and both sets had different problems. Very poor quality, and most all my stuff is from there. But not gauges.
I got my flush gun from these folks, and I think the HitMan might have got this kit.

http://cgi.ebay.com/ebaymotors/Automotive-Vacuum-Pump-AC-Gauge-Set-R134a_W0QQcmdZViewItemQQcategoryZ43989QQihZ002QQitemZ120128828204QQtcZphoto

I would go to http://www.ackits.com/merchant.mvc?Screen=SFNT&Store_Code=01 and get some Nylog to seal your orings at the joints, and they also have a Euro oring kit that was very handy. Remove all old orings, use new ones with Nylog, and you will almost never have a leak from these locations. Also get new Schrader valves for your fittings. If you are not going to use R12, I would get the R134A type fittings for either that or Freeze12. Just be sure to label if you use Freeze12 so a future AC guy's recovery equipment and supply isn't contaminated.
And, I'm not any happier with Freeze12 than I was with R134a. Not much difference really.
Also, that website sells parallel flow condensers that folks seem to think help the system work better, especially with R134a. Search for info on that. (parallel)
Listen to other opinions, see what you think.

veggie190 · #7 06-06-2007, 11:35 AM

Great, thanks for the info to stay away from the HF gauges. The combo on ebay isn't a bad price, I think I'll be doing that option.

Also thanks for the info on buying new o-rings for the connections. I want this to be done right and last, I plan on keeping this car as my daily driver for years ahead!

I really appreciate all the help!