[W126 Coupe] Heater stuck in "on" position

[Dick Spellman]

Hi Waldemar:

ACC power - I'd simply replace or swap fuse #5 in the big fuse box on 
the left side (driver's US side) (should be white and 8 amps rated) It 
does not matter if the fuse looks good, be sure and replace or swap 
since a visual check of the fuses does not always work.  # 5 is for 
power to the climate control push button unit.
Blower power -  Look for a black harness  going in and out of a flat 
black holder attached to the engine firewall on the driver's side just 
in front of the fuse box and brake master cylinder/booster.  Under the 
cover is a foil fuse (available from MB dealer and <$3 US) that provides 
power to the blower.

Regards,

Dick

Waldemar Kalinowski wrote:

>
> 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
>>>
>>>
>>> The MB Coupes Website!
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>>>
>> The MB Coupes Website!
>> W126 SEC Mailing List
>> Postings remain property of MB Coupes, L.L.C.
>
>
>
> The MB Coupes Website!
> W126 SEC Mailing List
> Postings remain property of MB Coupes, L.L.C.
>