[W126 Coupe] Heater stuck in "on" position

[Waldemar Kalinowski]

Hi Dick,
Thanks for quick response. This is a new problem and since it started few 
days ago it is constant. It is definitely hot engine air that's coming in 
through the vents. Could you let me know where the recspected fuses are 
located?  Since none of the climate controls are responding, I can not 
change any AC settings.
Thanks,
Waldemar

>From: Dick Spellman <spell.yy at verizon.net>
>Reply-To: Mercedes Coupes Mailing Lists <mbcoupes at mbcoupes.com>
>To: Mercedes Coupes Mailing Lists <mbcoupes at mbcoupes.com>
>Subject: Re: [W126 Coupe] Heater stuck in "on" position
>Date: Wed, 07 Jun 2006 21:26:15 -0400
>
>Hi Waldemar:
>
>I'd start with a check of the external foil fuse for the blower and the 
>fuse for the ACC.  Next would be the ignition switch.  Is this a constant 
>problem or is it sporadic?  For ex. one day you turn on the ignition and 
>everything works and the next day you turn the ignition and the ACC is 
>dead?  This would be a symptom of the ignition switch failing.  Next might 
>be bad solder joints on the ACC head unit harness pins.   Then there is the 
>question, does the AC clutch engage for air conditioning and you still get 
>hot air?  Then, I'd check the mono-valve which may be stuck in the open 
>position allowing engine coolant to flow through the heater core and 
>compete with the AC evaporator.   One way to clear this would be to place 
>the ACC in MAX AC and see if the stuck mono valve plunger frees up.  You 
>could try tapping the mono-valve head as well while in Max AC.  Last would 
>be the vacuum elements that could allow too much outside air to enter the 
>cabin through the fresh air door, defeating the benefit of the AC.
>
>Dick
>
>Waldemar Kalinowski wrote:
>
>>Hi Everyone,
>>Heater pumps hot air through the interior vents. Heater blower 
>>non-functioning.  None of the climate control buttons work. What would be 
>>the order of things to check out? How to disconnect the heater, at least 
>>temprarily?. Weather's getting hot in So Cal.
>>Thanks for advice.
>>Waldemar 1989 560 SEC
>>
>>
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>>
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