[W126 Coupe] MBCOUPES Digest, Vol 25, Issue 10

[Dick Spellman]

Hi Jack:

Just a few thoughts that may or may not help.  Set the ACC dial to 
coldest setting and 3rd button from right depressed, fan set to Auto.  
Disconnect the 2-wire connector at the top of the mono-valve.  Check 
this connector for 12VDC with a volt meter.  If it's giving you a 
voltage it's likely the ACC head unit has a problem.  If there is no 
voltage present then it's likely the mono-valve (new and all) is stuck 
in the energized (open) position allowing hot coolant to flow to the 
heater core.

You could probably check the auxiliary coolant pump in the same manner. 

Regards,

Dick

Jack wrote:

> Hi All,

>

> I have a question about the heating in a 500SEL.

> What would cause the heat to be on full blast?

> I've changed the mono-valve to no avail.

>

> I also have a 86 560SEC that I'm parting out.

> I saw someone looking for one with good body parts.

> This is an Arizona car with no rust, dents etc. with 156k on it. No

> accidents. It's had recent timing chain, rails tensioner, and a complete

> valve job. Tranny was rebuilt etc. It's been a money pit for years, not that

> I minded it at the time.  I've sold a few parts off it already, but don't

> have the time to work on it much anymore.

>

> Jack H.

>

>

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