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Old 03-10-2003, 06:24 PM
alex charles
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Heater control will only do hot - help.

Calll me a thick Englishman but I can't work it out.

I have just bought my first SL and no matter what setting I use, unless I turn on the AC, I can only get hot out of the far right and left vents and cool out of the middle.

Is this normal or am I mad ?

It may be bad weather in England but heat all the time ? there must be a better way ?

Last edited by alex charles; 03-10-2003 at 06:44 PM.
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Old 03-10-2003, 06:55 PM
Registered User
Join Date: Sep 2002
Location: Kingsport, TN
Posts: 375
Hi Alex,
I think it is normal. On an '87 420 SEL, the inner air ducts are for fresh or cool air, while the side and footwell outlets are for hot air.
The manual would tell, but you probably don't have one.
Reinhard Kreutzer
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Old 03-10-2003, 07:07 PM
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Join Date: Jul 2001
Location: SoCal
Posts: 1,303
Try closing down the center vents - the temperature out the side vents should fall, if it works like our newer 190E. However, with the heat turned all the way down, you shouldn't get any heat anyway.

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Old 03-10-2003, 07:38 PM
96C220's Avatar
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Join Date: May 2001
Location: Hamilton, NJ
Posts: 367
The MB HVAC system can confuse the best of them....

Footwell vents and Side Vents only provide heat....

Fresh / Cooled air is provided only by the center vents.

One thing I am suprised the Euro manufacturers didnt follow the trend on, was the bi-level heat / cool combo that the American manufacturers were big on in the 80's.

My friend had a camaro convertible, and it was the best feature.. A/C out of the front dash vents, but heat out of the floor vents to keep the feet warm.

It seems like anyone who has spent any time in europe knows that until very recently (late 90's) - A/C was an option not chosen by many, especially because of the lag it put on the smaller displacement engines. Because of that, the A/C systems in a lot of our 80's to 90's cars seem like an afterthought. That and the extremely sub par audio systems compated to other cars in this price range....Things have improved some, but its just not the same to see the door jamb say manufactured by daimler chrystler.

Oh well...

George Androulakis

Former Mb's:

1990 500sl R129 - 76k Original Miles - New project - Follow the saga
1990 190E 2.6 148k mi (sold)
1989 420 SEL 246k mi (sold)
1995 C220 175k mi (sold)
1992 190e 2.6 74k original miles (sold)
2000 c230 Kompressor 122k miles (RIP)
1996 C220 149k mi (sold)
2000 C230 Kompressor Sport 127k (sold)

Current Cars:

2009 Mercedes c300 4matic
2006 Mercedes s430
2005 Jaguar XJR
2003 Cadillac Escalade
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Old 03-10-2003, 08:26 PM
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Join Date: Jun 2001
Location: Omaha, NE
Posts: 962
The rationale for the situation you describe is that the side vents are intended to be turned toward the side windows in winter to defrost them. Kind of clever, using the same vents instead of newer vehicles with dedicated side window defoggers.

There is USUALLY some sort of logic to MB engineering. Defining it is a different story ...
'93 400E
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Old 03-11-2003, 02:34 AM
alex charles
Posts: n/a
I guess that makes sense. When it's hot I suppose you justs switch of the air flow to them.

However - you can't control the flow of air to the very front winidscreen blower.

Even when I turn down the two heater sliders in the central console to minimum it blows hot ?

I suppose if the fan is off - thee front blower won't put any air out even though the sides ones do.

Anyway - my enquiry seems petty compared to others problems.

Thanks for the help.
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Old 03-11-2003, 11:55 AM
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Location: Lathrup Village, Michigan
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There is USUALLY some sort of logic to MB engineering. Defining it is a different story ...
I don't know what they were thinking for the M-class.

The center vents are ALWAYS on, can't be closed off all the way, and is heated air, not fresh air.

For this reason alone, I find it difficult to ever want to drive the thing in cool/cold weather.
Michael LaFleur

'05 E320 CDI - 86,000 miles
'86 300SDL - 360,000 miles
'85 300SD - 150,000 miles (sold)
'89 190D - 120,000 miles (sold)
'85 300SD - 317,000 miles (sold)
'98 ML320 - 270,000 miles (sold)
'75 300D - 170,000 miles (sold)
'83 Harley Davidson FLTC (Broken again) :-(
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Old 03-11-2003, 07:37 PM
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Join Date: Jul 2002
Location: Devon, UK
Posts: 26
you have a fault. The centre vents as stated provide only fresh or cooled air (assuming you have AC) whilst all other outlets are under thermostatic control and should provide the full range from fresh or cooled through to hot.
My 300TE had the same problem before I bought it - the remedy was replacement of the electronic control panel of which the 2 thermostatic sliders form part (an expense fortunately met by the supplying dealer in my case).
Good luck!
90 300TE 24v (M104 eng) 207K miles
87 300TE (M103 eng) 269K miles (and never had the head off!)
86 300TE (M103 eng) 230K+ miles (donor car)
95 Toyota Lucida diesel 4wd
86 200T 165K miles (sold)
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Old 03-12-2003, 03:31 PM
alex charles
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Thanks Adrian,

thought it was going to turn out to be a fault.

Any idea of th cost ?
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Old 03-12-2003, 03:43 PM
alex charles
Posts: n/a
Thanks Adrian,

thought it was going to turn out to be a fault.

Any idea of th cost ?
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