[W126 Coupe] MBCOUPES Digest, Vol 52, Issue 36

[Dick Spellman]

Hi Robert,

I presume the 'cold' air does blow out into the leg areas when you call for
heat.  This would be correct for the vacuum system to close center vents and
open leg flap doors at least initially until the cabin gets to a certain
temp before air flaps cycle elsewhere too.

A possible quick fix is to dial the heat all the way to highest temp (you
will feel a click on the dial) and see if heat occurs after a minute or
two.  If it does the mono-valve is sticking but, you'll have heat
temporarily.

In any event, the mono-valve likely has a tear in the rubber diaphram.  The
mono-valve replacement kit is now about $40 (just did one yesterday after
85k on the last one).  It is a simple DIY'r job or ask a mechanic and it's
30 minutes work.  If you need the kit pronto, contact Jonathan and it will
usually arrive next day if you are on the east coast.  I'm ordering my spare
from him tomorrow.

Let us know how you make out.

Dick

On Sun, Dec 28, 2008 at 10:59 PM, btb management
<btbmanagement at hotmail.com>wrote:


>  Dear MBCoupes:

>

> Having a problem with my recently repaired 1985 500 SEC heating system.

> Over the summer my a/c was repaired, as it didn't blow out of the center

> vents

> from a prior repair which disconnected the hoses.  Had no prior problem

> with the heater,

> it worked fine.  Now that cold weather has set in, when the heat is turned

> on it

> blows out cold, except when the defrost button is used and it sounds like

> there is some

> door switching open and hot air comes out.

> Any thoughts as to why the heater blows no hot air?

> Something must not have been

> reattached during the a/c repair is my thought.

>

> Thanks,

> Robert

>

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