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  #1  
Old 09-18-2010, 06:17 PM
WANT '71 280SEL's Avatar
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Location: Dallas, TX
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AC blows cold, but still getting heat out side vents (water valve sealed shut)

I cannot only get air conditioned air blowing out of my vents. In the center vents, I get about 60F running around town. The faster I go, however, the warmer the car gets. I have sealed off the water valve under the hood so coolant isn't circulating through the core, but the air is so hot it feels like it's engine bay heat? I have the side vents closed off, so no hot air comes in there, but the blower is blowing hot air out the driver's side windshield vent! If I could get this thing to stop blowing heat when the A/C is on the car would stay pretty cool I know the right side heater lever is broken, but does switching on the heat, using the lever, change the source of ambient air? When the heat is on, doesn't it get the air from the same place as the AC? I thought both systems pull in air from the windshield cowl?

Any help would be greatly appreciated as Dallas is pretty hot.

Thanks,

David
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  #2  
Old 09-19-2010, 12:26 PM
WANT '71 280SEL's Avatar
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When starting the car this morning, I realized it definitely has to be heated air, whether it be from the engine bay or heater core. When the car was first started cold, the air coming out the defrost vent (not as strong as the center or side vents) was cold. As the engine warmed up, so did the air. The car was parked the whole time in the shade so the ambient air didn't get any warmer during the engine warm up period.

Thanks,

David
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2000 Honda Accord V6 137k miles

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  #3  
Old 09-19-2010, 05:56 PM
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Location: Central Ky
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Id say you are just getting engine heat into the vent . The flap may be open ( stuck) or not sealing properly. What does your manual say about AC and where you should feel it. IIRC its only the center vents
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Ron
2011 Porsche Cayman - Bond,James Bond
99 E320 THE Queen Mary
62 220b - Dolly - Finally my Finny!
72 450SL, Pearl-SOLD
16 F350 6.7 Diesel -THOR
07 Lexus RX 350 - Lexi
14 38HP John Deere 3038E Tractor -Mean Green
84 300SD, Benjamin -SOLD
71 220 - W115-Libby ( my first love) -SOLD
73 280 - W114 "Organspende" Rest in Peace
81 380 SL - Rest in Peace
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  #4  
Old 09-19-2010, 07:16 PM
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Location: Dallas, TX
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I removed both kick panels and patched the hole in my air box. Then, I saw that my right side lever had the air door partially opened. It was stuck, so I removed the nut from the lever and manually moved the door. I could feel the air go hot when moving the arm. So, I moved it so the air felt cooler (I say cooler because I don't know that it's really air conditioned air) and tightened the nut down. Right now, I get moderately cool air out the side vents, nothing to the windshield (THANK GOD!!!!) and 60F air out the center vents with an ambient temp in the 90-95 range. It's not the best system in the world, but it isn't uncomfortable, either.

The system's on R12 right now with a new compressor. I didn't replace the drier as I should have but that's because I was in a hurry and didn't have one with me at the time. Now to diagnose my electric fan that doesn't come on when the temp rises or pressure rises. I jumped the wires and nothing happened but sometimes they come on. Oh old German cars...it's always something. I'm just glad to have the heat stop pouring into my car!

Are the side vents supposed to be very cold air? It seems like they're routed to get the AC air but the evaporator seems to be right in front of the center vents so the side vents get the left-overs.

Regards,

David
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2000 Honda Accord V6 137k miles

1972 300SEL 4.5 98k miles

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  #5  
Old 09-19-2010, 09:08 PM
meltedpanda's Avatar
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these cars were never know for good AC systems, if you are getting 60 degree air out of the center vents and semi cold from the sides vents, count yourself lucky!
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Ron
2011 Porsche Cayman - Bond,James Bond
99 E320 THE Queen Mary
62 220b - Dolly - Finally my Finny!
72 450SL, Pearl-SOLD
16 F350 6.7 Diesel -THOR
07 Lexus RX 350 - Lexi
14 38HP John Deere 3038E Tractor -Mean Green
84 300SD, Benjamin -SOLD
71 220 - W115-Libby ( my first love) -SOLD
73 280 - W114 "Organspende" Rest in Peace
81 380 SL - Rest in Peace
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  #6  
Old 09-20-2010, 01:50 AM
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I don't know, if it's the 4.5... I remember ice forming on the center vents on longer highway trips on 90+ days. I would say if it's 60, something is wrong. Never had experience with a 116 to call that one.
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  #7  
Old 09-20-2010, 03:01 PM
meltedpanda's Avatar
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going by my SD's of past and the 220
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Ron
2011 Porsche Cayman - Bond,James Bond
99 E320 THE Queen Mary
62 220b - Dolly - Finally my Finny!
72 450SL, Pearl-SOLD
16 F350 6.7 Diesel -THOR
07 Lexus RX 350 - Lexi
14 38HP John Deere 3038E Tractor -Mean Green
84 300SD, Benjamin -SOLD
71 220 - W115-Libby ( my first love) -SOLD
73 280 - W114 "Organspende" Rest in Peace
81 380 SL - Rest in Peace
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  #8  
Old 09-20-2010, 05:04 PM
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Location: Atlanta, GA
Posts: 293
Please tell us which car you are referring to.
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J. P. Mose
1968 250SL
1970 280SE 3.5 Cabrio
1987 560SL
1990 560SEL
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  #9  
Old 09-21-2010, 09:54 PM
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JPMOSE, I was talking about my 450SEL, a w116.
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  #10  
Old 09-22-2010, 03:18 PM
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Location: Atlanta, GA
Posts: 293
Now that we know what car you're referring to, more info may come your way. First and foremost, please join the following forum, which has more information on W116 cars than any:

http://www.w116.org/

Look under LIBRARY and access the Service Manual Library in the upper right corner. This is the factory CD set for free!!! There is a climate control manual as part of it. Your system is the earlier manual configuration. My W116 had the automatic and was quite different (and very complicated!).

I would post your question(s) on that forum and you'll likely get a lot of answers. My W116 A/C had R12 refrigerant and yielded cold air even in Atlanta's hot summers (I used to live in Fort Worth and understand you situation with heat). The W116 A/C system's only drawback was less fan volume than the later W126 (which was not as good as the W140).

You haven't mentioned whether the refrigerant capacity is within specifications. The plenum chamber is controlled by vacuum actuators, even though the levers on the dashboard appear to be similar to W108/109 and earlier configurations. A major vacuum leak would cause the entire system to dis-function. The upper dial on your climate control panel will engage the cooling system when the dial is turned counter-clockwise....continuing to the farthest turn will operate the cooling system in Recirculating Air mode (80% Recirculated/20% Fresh). This is a must for cooling down more rapidly. But even 100% Fresh air should provide some cooling and NOT HOT AIR.

I would download the climate control manual and study it well. If you're handy with cars, I would use a vacuum gauge with hand pump to see whether you have a leak or not. If so, you will need to go through the entire system to isolate the leak(s). The vacuum actuators are likely leaking if they have never been replaced or rebuilt.

George Murphy has a lot of knowledge on the W116 system (especially the very complicated automatic system). Here is his contact information.

http://www.dianasmercedes.com/PAC.htm

He also has a catalog that he can send you. He further knows how to convert the recirculating door so that the output will be 100% recirculated air, which is a major difference in a hot climate such as Dallas.

Good luck with this...but be assured that your system will blow cold air even on 100 degree days with everything working correctly (even better with George Murphy's modification)!
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J. P. Mose
1968 250SL
1970 280SE 3.5 Cabrio
1987 560SL
1990 560SEL

Last edited by JPMOSE; 09-22-2010 at 04:14 PM.
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  #11  
Old 05-20-2013, 12:06 PM
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Posts: 12
Hey J. P.,

I'm having similar issues with my 85 W126. The first symptom was the heat was on all the time. Then the AC went out. After much troubleshooting, my mechanics replaced the AC regulator, and that brought the AC back, but the heat is still on and now the tach stopped working. Any tips?
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  #12  
Old 05-20-2013, 10:25 PM
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If you are only getting it down to 60F something is wrong. I just charged my r134a converted w108 this weekend, I know it's underchaged, but still got 55F out the vents with the car sitting still.

Csaba
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  #13  
Old 05-20-2013, 11:02 PM
WANT '71 280SEL's Avatar
I'll Go Upside Your Head!
 
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Location: Dallas, TX
Posts: 3,378
This is an old thread. It turned out that coolant was still going through the core and heating the air in the vents. Once I fixed that, I got A/C into the mid-40's. The car was a w116.

Thanks,

David
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2000 Honda Accord V6 137k miles

1972 300SEL 4.5 98k miles

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  #14  
Old 05-20-2013, 11:51 PM
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Duh! Sorry, I should have checked the dates...

Csaba
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