Author Topic: A/C nightmare  (Read 318 times)

larrud

  • Newbie
  • Posts: 1
  • W116 Enthusiast
  • Location: North Fort Myers, FL
A/C nightmare
« on: 20 May 2020, 11:31 PM »
Help! I’m dying from heat stroke. Just got my 73 back from 16 months of reconditioning with complete mechanical restoration and new interior. Car is wonderful with one MAJOR problem. The AC blows piping hot air through the outside upper and lower door registers. I live in SW Florida so the car cannot be used. The people who worked on it just shrug  :'(

Has anyone else had to deal with this? Any solutions? Upgrades? Off the wall replacements? I will entertain any idea that will work, no matter how unconventional. I’m not being a purist. I have a gorgeous old first year perfect 116 that I cannot use. Thanks for any and all suggestions

daantjie

  • W116 Addict
  • ****
  • Posts: 1,900
  • W116 Enthusiast
  • Location: Vancouver, BC, Canada
Re: A/C nightmare
« Reply #1 on: 20 May 2020, 11:36 PM »
Need more info.  What model, Euro or US spec, manual AC or Automatic Climate Control?
Maybe post a pic of the control panel so we can see what you have.
Daniel
1977 450 SEL 6.9 - Astralsilber

revilla

  • Classic
  • **
  • Posts: 298
  • W116 Enthusiast
  • Location: Aix-en-Provence, France
Re: A/C nightmare
« Reply #2 on: 21 May 2020, 04:18 AM »
Diagnosing the problem will take time, but you asked for even unconventional solutions. One of them would be to bypass the rubber hose that enters your cockpit on the right of the firewall and exists on the left side of your engine. This ‘temporary solution’ will avoid the hvac core to become hot and blow hot air all the time. To bypass it you’ll need a couple of elbows and about one meter of hose capable to handle the pressure/temp.
Once bypassed, you can at least drive your car while you solve the true root cause. Most likely, others can chime in, the problem is the valve connected to a red vacuum line on the firewall engine side that is not closing properly, letting therefore hot water circulate, which causes your AC to blow only hot air. The second usual suspect is the 2 flaps mechanisms around the core unit that lost their foam isolation and/or their capacity to closed completely as it was the case in one of my cars. It took a while to solve because access is VERY difficult but I was able to solve the problem weeks later after the bypass operation.

Good luck.

Robert
 
Robert
W116 1977 280SEL & 1979 280SE

UTn_boy

  • W116 Addict
  • ****
  • Posts: 1,248
  • Chrome Bundts & bundts with white walls are a sin!
  • Location: knoxville, tn
Re: A/C nightmare
« Reply #3 on: 21 May 2020, 02:56 PM »
Need more info.  What model, Euro or US spec, manual AC or Automatic Climate Control?
Maybe post a pic of the control panel so we can see what you have.

He notes that he has a 1973 year model, and automatic climate control didn't come about until fall of 1975, so his will have manual climate control.  So U.S. or Euro spec won't have any bearing on us helping him.  Though, Revilla's commentary is a wonderful start. 

A silly question, but are all of your control levers and knobs in the proper position for no heat and AC on?  You'd be surprised how many people aren't aware of how the control levers work, and that one of the 4 slide levers has to be opposite of the other three when the A/C is on or being used. 
1966 250se coupe`, black/dark green leather
1970 600 midnight blue/parchment leather
1971 300sel 6.3, papyrus white/dark red leather
1971 280sel Black/black leather
1973 300sel 4.5, silver blue metallic/blue leather
1976 280s astral silver/blue MB Tex

BCDC

  • Enthusiast
  • *
  • Posts: 41
  • W116 Enthusiast
  • Location: Tasmania
Re: A/C nightmare
« Reply #4 on: 21 May 2020, 03:21 PM »
The AC in my car works fine apart from a slightly noisey compressor but my heating sliders will not go completely to the bottom for the totally off position. Is there something going on here? I've seen pictures of these right at the bottom of the travel.

BC
1978 280SE Cream with blue interior. With SLS

revilla

  • Classic
  • **
  • Posts: 298
  • W116 Enthusiast
  • Location: Aix-en-Provence, France
Re: A/C nightmare
« Reply #5 on: 22 May 2020, 04:11 AM »

A silly question, but are all of your control levers and knobs in the proper position for no heat and AC on?  You'd be surprised how many people aren't aware of how the control levers work, and that one of the 4 slide levers has to be opposite of the other three when the A/C is on or being used.

Thanks Aaron. You’re right. I assumed too quick all knobs/levers were in AC mode (zero heat) before entering into the bypass temporary solution. I failed to mention too that once problem is root caused and solved, the bypass has to be removed. Maybe too obvious but better to point that out later than never.

Up to ‘larrud’ now to confirm his status.

Robert
W116 1977 280SEL & 1979 280SE

TJ 450

  • W116 Addict
  • ****
  • Posts: 4,235
  • Location: Rockingham, Western Australia
    • Tim's Insulators Downunder
Re: A/C nightmare
« Reply #6 on: 22 May 2020, 06:58 AM »
If it is the manual HVAC setup then a possible scenario is the vacuum lines being hooked up incorrectly.

A temporary solution would be to manipulate the heater valve in the engine bay so it stays in the off position.

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

revilla

  • Classic
  • **
  • Posts: 298
  • W116 Enthusiast
  • Location: Aix-en-Provence, France
Re: A/C nightmare
« Reply #7 on: 22 May 2020, 10:20 AM »

A temporary solution would be to manipulate the heater valve in the engine bay so it stays in the off position.

Tim

That’s right Tim. That was my 1st attempt, but the valve itself together with the vacuum actuator was malfunctioning, letting still refrigerant circulate.  Then I resourced to the bypass option. However, your idea made me think of a possible easier way to isolate the core from the circuit while the problem is diagnosed so he can at least drive his car in hot Florida: simply disconnecting one of the 2 in/out hoses in the engine bay and adding 2 plugs (temporarily). That should have the same core isolating effect than your idea of forcing the heat valve close (providing it’s in working condition, mine wasn’t) and he won’t need to add a bypass hose/elbows/screw-hose-clamps/etc.  That could work.

Let’s see what he finds.

Robert

Robert
W116 1977 280SEL & 1979 280SE

revilla

  • Classic
  • **
  • Posts: 298
  • W116 Enthusiast
  • Location: Aix-en-Provence, France
Re: A/C nightmare
« Reply #8 on: 22 May 2020, 10:29 AM »
The AC in my car works fine apart from a slightly noisey compressor but my heating sliders will not go completely to the bottom for the totally off position. Is there something going on here? I've seen pictures of these right at the bottom of the travel.

BC

Hi BC,

I’ve seen that. If you remove the knee panel (left or right depending which lever isn’t moving all the way up/down) you’ll see the adjustment bolts and rods. There are 3 on each side if I recall correctly. It’s not very intuitive, at least for me it wasn’t.  I adjusted them by trial and error. There might be a procedure somewhere to do this job. BUT, it could also be the flaps that are jammed (I’ve seen that too).  No joy...

Please let us know of your findings.

Robert
Robert
W116 1977 280SEL & 1979 280SE