A/C problems, help needed. - Page 3 - PeachParts Mercedes-Benz Forum

leathermang · #31 07-30-2011, 05:31 PM

Quote:

Originally Posted by BSharp

I have put oil back in after each flush. Except today, I am thinking about going to the wrecking yard and comparing back pressure on a cond compared to mine. Yuk

Not sure I understand these sentences...
' Except today' .... referring to NOT putting oil back in today..??

BSharp · #32 07-30-2011, 05:41 PM

Quote:

Originally Posted by leathermang

Not sure I understand these sentences...
' Except today' .... referring to NOT putting oil back in today..??

Yes, oil is going back in. If I go to the wrecking yard and test another cond and it flows better than mine, I will get a new cond before I put oil in the system.

BSharp · #33 07-30-2011, 05:45 PM

Quote:

Originally Posted by leathermang

Elaborate on the ' multiple routes for the freon to go '.... in the evap cleaning...

Did you not convert the old TXvalve into a ' TOOL' as the FSM suggests for the purpose of flushing the evaporator ?

No, I just removed the expansion valve and flushed it. The evap has a common manifold where the tubes connect. It is feasible for a small amount of flush to hide in a corner (though unlikely).

leathermang · #34 07-30-2011, 05:51 PM

Quote:

Originally Posted by BSharp

No, I just removed the expansion valve and flushed it. The evap has a common manifold where the tubes connect. It is feasible for a small amount of flush to hide in a corner (though unlikely).

If flush is hiding there ... then moisture could be also..
suggest instead of air compressor air ( if you have compressed air from a welding supply it would be dry and fine ) you use nitrogen or Argon to push flush and evaporate afterwards..
and perhaps MB knew something critical when suggesting making the old Txvalve into a tool for flushing ?
You have done a lot of the stuff right.... but it shows how important each thing in an AC system is when you are in Texas...
If you flush it again... how about changing to Castrol Cold flow premium mineral oil just for grins.... and of course change out the oil in your vacuum before vacuuming the next time....
You are pretty much keeping some ac shop in business selling rec-driers....

BSharp · #35 07-31-2011, 10:30 PM

Well, I flushed the system, replaced the drier, blew though everything, added about 6 oz of ester oil, vacuumed for 1 hour, but in 3 cans of R12. And cools to a chilly 70 F. I did everything right and it still will not cool. I have done other systems without as much attention to detail and never had this happen. I am now thinking the cond. may be the problem. I think the evap is not getting enough freon flow. The high is a little too high maybe because of a restricted cond. I wish there was a way to get a pressure reading between the cond and evap.

leathermang · #36 07-31-2011, 10:50 PM

That was not much time vacuuming..... for someone that thought they might have a moisture issue.....
and you did not do a leak test by pressure ?
and did not change to Castrol cold flow 500 oil....

BSharp · #37 08-01-2011, 12:20 AM

An hour should have been plenty long. I also let it sit for an hour with no vacuum loss at all. I tried to find the Castrol stuff but did not have any luck. I did put in new fresh ester oil. The expansion valve I installed did say R134 but from what I have read it should make a real difference. I have done a lot of a/c over the years but this one has me stumped. There is nothing in this system that is all that different.

BSharp · #38 08-01-2011, 09:08 PM

Update. I did not drive the car today, drove my truck to work. Came home and started to car, I was going to check the switch-over valve and vacuum lines. Before I did anything I started it and turned on the a/c. Hmmm seems to be cooling rather quickly. Idling it is staying about 62 F. I figure it is a fluke and wait a little longer, staying steady. Ok, time for a test drive. Cooling better while moving, down to lower 50s , then realize the recirc turned itself off after 30 mins. Reset it and gets down to 47-48 F. Looked at the sight glass it it is actually clearing up. WTH, did not work yesterday, would not get under 70, now working better that it did with R134a. I was going to check the pressures but I am afraid to mess with it.

vstech · #39 08-01-2011, 11:55 PM

Quote:

Originally Posted by BSharp

An hour should have been plenty long. I also let it sit for an hour with no vacuum loss at all. I tried to find the Castrol stuff but did not have any luck. I did put in new fresh ester oil. The expansion valve I installed did say R134 but from what I have read it should make a real difference. I have done a lot of a/c over the years but this one has me stumped. There is nothing in this system that is all that different.

PLEASE go read the first few posts in the a/c sticky...

I'm glad your system is cooling adequately now, but, proper setup and testing is important to a long lasting a/c system.

BSharp · #40 08-02-2011, 12:12 AM

I did read the thread. I was not so much worried about leaks as I was about why it was not cooling.

leathermang · #41 08-02-2011, 11:01 AM

Quote:

Originally Posted by BSharp

I did read the thread. I was not so much worried about leaks as I was about why it was not cooling.

Vacuuming is not a good way to test for leaks.

Pressure is the only legit way.... for reasons described by VStech...in that thread...

Vacuuming one hour --particularly if one is trying to sort out hard to find problems--- is not enough to make sure you have the moisture out....

I hope your problem is fixed and it works great from now on...but if it does not... you are in the same place you started from...
not having used the proper procedures to makes sure you eliminate the possibilities one at a time.....

BSharp · #42 08-02-2011, 11:48 AM

I was not trying to find leaks, that is why I did not pressurize it. And the last time I filled the system I had flushed it and let it sit overnight (not the drier). According to the Mobile Air Conditioning Society 30-45 mins is sufficient. http://www.macsw.org/AM/Template.cfm?Section=auto_a_c_climate_protection_pledge&Template=/CM/ContentDisplay.cfm&ContentID=6252
This is what I did the last time.
Flushed the lines
flushed the evap
replaced the expansion valve
replaced the drier
removed the flushed the cond.
drained the compressor
installed 6-7 oz of new unopened ester oil
vacuum system for 1 hour
watched gauges for vacuum leaks (I know, not the same as pressure testing the system. If I has a reason the think it might leak I would have)
Installed 38 oz of R12.

I appreciate the tips, it has helped.

BSharp · #43 06-28-2012, 09:53 AM

I forgot to update on another problem I found. I had replace all my vacuum pots when I replaced the dash. Once I had got the A/C working it was ok at idle but not very good while driving. I did not make sense. After checking everything multiple times I noticed that when I put my temp probe in the center vent while stationary it would be ok, in the 50's. But when driving it would be in the 60's. I put the probe further in, almost touching the evap and it was in the 40's while driving. I know my heater core was not flowing. I started to think about the recirc door. I pulled the blower motor and checked it. Sure enough, the hinge was broken. Even though the actuator was working since the hinge was broken cowl air pressure at speed was allowing warm air in. This is why it was acting the oppisite way than normal. Since there is not way to fix it with the dash installed I cut a piece alum the same shape as the opening (14"x2") and siliconed it in place. I still have to hit the recirc button to get better air flow but the a/c works great (worked, my cond sprung a leak and could not be fixed. A new one should be here tomorrow, the last new one in the country. 87 190D turbo uses one different from all other W201s). So check your fresh air flap hinge on your W201s and W124s (assuming they are the same).

Bob338 · #44 06-28-2012, 01:27 PM

Your center vent, when open, allows outside air. That's why your temperature rises.

What I don't understand is your getting refrigerated and cold air from the center vent. That vent is not normally fed by the refrigerated air. Your owner's manual should make that clear, as mine does. For max cooling, you are instructed to close the center vents. It's the same on all 201's.

BSharp · #45 06-28-2012, 01:53 PM

If you look through the center vents you can see the evap. Weather the center vent is open or closed if the recirc button is pushed outside air should not be comming in. Regardless, the issue I had was outside air was being forced into the cabin even though I had the recirc on. The evap was tring to cool 100 F air instead of 60 F. It is a cheap design, the hinge is made of plastic and breaks.