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  #1  
Old 02-17-2006, 04:49 AM
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70 degree days are back. Some AC help needed

Hi all,

Warm weather has come a bit early and I have had to move up my AC repair work. This is on my 300D. I would like some input on where I should start on my search for the non-functioning system.
This car has been, as someone else on the board had refered to as, southern engineered. The blower works as (I think) it should. Move the dial and the speed increases. When the dial is at 4, the blower runs slowly at first and when the engine warms up (?), it blows at full force. The air flow selector (defroster, heater, vent) works, mostly. No matter what position the selector is in, there is always a good amount of air coming out of the vents. When I select the vents, the air volume increases from the vents. Nothing seems to happen when I press the AC button, so I keep it on Economy all the time. When I have done my limited invistigation, the AC button did not work. The small red light shines, but no effect on the air coming out. The temp dials do not work. To turn on the heat you have to depress the toggle switch that is next to the recirc switch. The air, when the heat is 'on' blows at one temp, friggin hot. The only way I can control the temp is mixing the outside vents (hot) with the middle vents (cold).
Under the hood, there is something that I am sure was not standard MB design. There is a shut off valve on the heater hose.
There is no way to contact the PO (this was an estate car apparently), so I have no idea what was done (and more importantly, why) and what I need to do to get it going (the correct way) again.
Living in Alabama, 95 degree and 100% humidity days will be a reality sooner than I want.







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Old 02-17-2006, 08:43 AM
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When you hook gauges to the system what pressures are you reading?
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  #3  
Old 02-17-2006, 10:08 AM
Brandon314159
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I dunno about you but personally its been in the low teens here (close to setting coldness records).

The AC is not getting much use (other than for drying out air!) hehe
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Old 02-17-2006, 10:11 AM
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I'd dump that ball valve. Is the AC compressor engageing? If not you may have low freon.
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  #5  
Old 02-17-2006, 01:40 PM
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Quote:
Originally Posted by dannym
When you hook gauges to the system what pressures are you reading?
I am a total novice at all of this DIY stuff, but am an eager learner. What guages hooked where are you refering?

Thanks for your help,
Dale
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  #6  
Old 02-17-2006, 01:42 PM
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Quote:
Originally Posted by Hatterasguy
I'd dump that ball valve. Is the AC compressor engageing? If not you may have low freon.
I was thinking about removing it, but since there must have been SOME reason the PO installed it, I was a bit reluctant to do so. Any ideas why someone would do this?
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91 190E 2.6 5 speed 220k miles and this car still scoots!
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  #7  
Old 02-17-2006, 09:04 PM
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Quote:
Originally Posted by fantom71
I am a total novice at all of this DIY stuff, but am an eager learner. What guages hooked where are you refering?

Thanks for your help,
Dale
I was refering to air conditioning gauges like these:
http://www.ackits.com/merchant2/merchant.mvc?Screen=PROD&Store_Code=AMA&Product_Code=35772
You won't get very far without them.

A simple test you can do now to check the compressor is short out the wires to the pressure switch on the dryer. If the compressor starts good. If not it may need to be replaced.
Don't worry if you short out the wrong switch. The other one starts the auxiliary fan.

Another good site:
http://www.airconditioning.com/start.htm

Another good idea would be to pick up an automotive ac repair guide. They can be found at probably all auto parts stores.

Danny
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  #8  
Old 02-17-2006, 09:52 PM
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its only 80 degrees cooler here wo the wind chill

shut up!!!




Quote:
Originally Posted by fantom71
Hi all,

Warm weather has come a bit early and I have had to move up my AC repair work. This is on my 300D. I would like some input on where I should start on my search for the non-functioning system.
This car has been, as someone else on the board had refered to as, southern engineered. The blower works as (I think) it should. Move the dial and the speed increases. When the dial is at 4, the blower runs slowly at first and when the engine warms up (?), it blows at full force. The air flow selector (defroster, heater, vent) works, mostly. No matter what position the selector is in, there is always a good amount of air coming out of the vents. When I select the vents, the air volume increases from the vents. Nothing seems to happen when I press the AC button, so I keep it on Economy all the time. When I have done my limited invistigation, the AC button did not work. The small red light shines, but no effect on the air coming out. The temp dials do not work. To turn on the heat you have to depress the toggle switch that is next to the recirc switch. The air, when the heat is 'on' blows at one temp, friggin hot. The only way I can control the temp is mixing the outside vents (hot) with the middle vents (cold).
Under the hood, there is something that I am sure was not standard MB design. There is a shut off valve on the heater hose.
There is no way to contact the PO (this was an estate car apparently), so I have no idea what was done (and more importantly, why) and what I need to do to get it going (the correct way) again.
Living in Alabama, 95 degree and 100% humidity days will be a reality sooner than I want.





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currently
[1981 300 td tdidi 165500 dark brown/palamino-Brownie-mine-3k miles of ownership
1983 240d 162+++ Anthricite grey w/ henna red interior and hella lights-wifes car-Red

the above two cars are for sale
and can be seen on the cars for sale thread here. pix also available.


240d-144+ Manilla Yellow w/ palmino interior-greasecar kit-Blondie-the college kids car

23" gt 21 speed still on original tires-still got the nubs
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  #9  
Old 02-17-2006, 11:50 PM
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83-240d

Quote:
Originally Posted by 83-240D
shut up!!!

If it makes you feel any better, it dropped down to an extremly fridgid high of 46 today. Actually, in this part of the world we have varying extremes. Sunday, we had lows in the low 20's and a 1/4" of snow, the middle of the week was in the 70's and tomorrow it is looking like we will get about 1/2 to 1" of ICE (freezing rain) and up to 2" of sleet on top of that. If that does happen, bad things are to come...
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91 190E 2.6 5 speed 220k miles and this car still scoots!
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  #10  
Old 02-18-2006, 11:13 AM
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Location: Geographically challenged on the S.W shores of Lake Michigan in S,E Wisconsin
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46 is shorts weather up here.

-6. one car started. one didn't.
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currently
[1981 300 td tdidi 165500 dark brown/palamino-Brownie-mine-3k miles of ownership
1983 240d 162+++ Anthricite grey w/ henna red interior and hella lights-wifes car-Red

the above two cars are for sale
and can be seen on the cars for sale thread here. pix also available.


240d-144+ Manilla Yellow w/ palmino interior-greasecar kit-Blondie-the college kids car

23" gt 21 speed still on original tires-still got the nubs
21" khs tandem
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  #11  
Old 02-18-2006, 12:21 PM
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Make sure that you know what kind of refridgerant is in the system before you do anything. There is a rather good chance that it has been converted to HFC134a, which will change your ideal pressures considerably.

If the connections have been converted, you know for sure that the system no longer contains CFC12. I've seen converted cars without the proper connections.
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  #12  
Old 02-18-2006, 02:03 PM
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Quote:
Originally Posted by fantom71
If it makes you feel any better, it dropped down to an extremly fridgid high of 46 today. Actually, in this part of the world we have varying extremes. Sunday, we had lows in the low 20's and a 1/4" of snow, the middle of the week was in the 70's and tomorrow it is looking like we will get about 1/2 to 1" of ICE (freezing rain) and up to 2" of sleet on top of that. If that does happen, bad things are to come...
Sooooo, thanks for rubbing it in....-12 last night.
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  #13  
Old 02-19-2006, 12:37 AM
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Quote:
Originally Posted by Matt L
Make sure that you know what kind of refridgerant is in the system before you do anything. There is a rather good chance that it has been converted to HFC134a, which will change your ideal pressures considerably.

If the connections have been converted, you know for sure that the system no longer contains CFC12. I've seen converted cars without the proper connections.
Is there a way to tell when I cannot talk with the PO?
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  #14  
Old 02-19-2006, 09:51 PM
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The R-12 use the Schrader Sp? fittings. They are the threaded fittings like on a bicycle tire.

The 134A fittings are a quick connect fitting. They are not threaded. They will have a lip near the top.

What happened when you did that test I mentioned?

Danny
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  #15  
Old 02-19-2006, 10:56 PM
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You really need a plan

Hey there,

I suspect the ball valve was to replace the mono-valve that most likely quit, explains the blow only hot issues. this becomes your temp control valve, the PO must have used fan speed to regulate temperature in the winter, probably shut the valve off completely in the summer months. also, you may, cause, as they do, have one or more of the 7 vacuum modules in the air handling box blown. Fail vacuum modules keep the internal doors from operating correctly again the blow hot gig.

Far as the compressor is concerned you can by-pass the low pressure control switch ahead of and under the abs pump, IF, has ABS, not all the euro 124s had it or airbags for that matter, (left front fender-well) on the receiver dryer. This will give you the quickie check on the freon level without refrigerant gauges. If the compressor clutch engages and the compressor runs, AND you get cold or cooler air, you found it, otherwise if it's cold, you have other issues. The type won't matter for now until you can tell if you have compressor function and freon present. The low and high pressure switches protect the system and the compressor from damaging it self and prevent operation.

Look for a blue benz part number stick over or near the original red freon charge quaintly sticker on the radiator support. Blue is for retro fits to 134, red is from r12. a quick familiar eye balling of the service ports IF AND ONLY IF, the converting mechanic installed 134 fittings will give it away also. I DID NOT on three of the cars I own, names because my gauges were for r12 and fit. if i installed the 134 fittings, then i needed new hoses, to that i say WHY? until i sell, then i will, but i've marked them 134 anyway.

Soo--that's my best shot, get a 124 Climate control manual to guide you, there are british versions out there that cover your car, and if I'm not mistaken the us manual covers most of the components as well, I just don't remember if it covers the manual system entirely. The 201 manual system is similar enough to yours to gump your way through it, i.e., look for a 2901 climate control manual as well.

cross your fingers, maybe some of the senior heavies will weigh in on this and help.

good luck,
mark

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