[W126 Coupe] Is this a monovalve problem?

[Dick Spellman]

Hi Tom:

I sniped the following from a post I did when replacing the ACC head unit.

""check that there in no reading at or close to 0-ohms resistance on 
both the mono-valve head and the coolant recirculating pump as an 
external short on either of these components will damage and void the 
warranty on the acc push-button unit". So, as an additional test you can 
and should check these two devices with an ohm meter with electrical 
disconnected to see if they are working showing and open vs. a short as 
the instructions recommend. I tested both my units before installing the 
new head unit and found them to be in working order. I took the added 
step of running 12VDC across each unit to see/hear the operation was as 
it should be... Clicking on the solenoid element for the mono-valve and 
the buzz and sounds of coolant being pushed though the heater core on 
the recirc. pump."

So Tom, with engine off and a quiet setting.  Disconnect both the 
monovalve electrical harness and the auxiliary pump harness that is 
directly below the mono valve.  Use two jumpers (I've used 18ga for 
short periods, no problems on everything but the acc blower without 
lighting up the jumpers).  Jumper one lead to ground and the other to 
battery positive on the aux pump and listen for the sound of moving 
water.  You should be able to hear a bit of gurgling.  On the mono-valve 
you should hear the click on/off but there is always the chance the 
rubber seal is cracked so even if the solenoid is actuating you've got 
the valve leaking or fouled.  Best to pull the head and have a look and 
test it on a bench.

I did not measure the amount of current being drawn by the recirc motor.

Hope this helps you find the problem.

Dick

Tom Oelsner wrote:

> Hi Dick

> See Below

>  

>  

>

>     -----Original Message-----

>     *From:* mbcoupes-bounces at mbcoupes.com

>     [mailto:mbcoupes-bounces at mbcoupes.com]*On Behalf Of *Dick Spellman

>     *Sent:* Thursday, December 07, 2006 4:13 PM

>     *To:* Mercedes Coupes Mailing Lists

>     *Subject:* Re: [W126 Coupe] Is this a monovalve problem?

>

>     Hey Tom:

>

>     Could be mono-valve then again maybe not.  If you throw the temp

>     dial until it clicks in the red, do you get hot air?   Not until I

>     am standing still.   If you then throw it to click in blue do you

>     get cold air?   Yes  If you then throw it in the red but, not all

>     the way to the click do you get hot air?  Not if f I am driving. 

>

>     Another way to test the mono-valve(s) directly is to apply 12vdc

>     to the 2 pin terminal atop the valve and see if you get hot

>     air.   What current? Other possibilities are ignition switch, or

>     climate control head or possibly a sticking fresh air make up door

>     which would be the two vacuum element flap up under the passenger

>     dash.

>

>     Anyway, you need to test further and report your findings.  If you

>     are inclined, just pull the mono-valve head and see if it's 1.

>     fouled with sludge and 2. showing signs of a ruptured rubber

>     seal.  If sludge only clean and re-install, if ruptured, replace.

>     ($20-40 depending on where you buy MB stuff)  I figure I'll do it

>     when I am taking time off from work at the end of the month. 

>

>     Regards,

>

>     Dick

>     btw:  took a position this past summer in the Northeast for a

>     company with US hq's in Sunnyvale (home of fantastic sushi) and

>     world hq's in Kobi and Kyoto, Japan (home of world's best steak,

>     would you believe?)  Same field as before just doing more work for

>     the US govt as a result.  Having fun too.  Let me know how the new

>     job is going.

>

>     .toelsner at comcast.net wrote:

>>     Happy Holidaze to Everbody,

>>     Well it is finally getting cold enough to turn on the heater in

>>     the mornings...now here is the scenario.

>>     When the car warmed up enough to turn on the heater, it was only

>>     blowing mildly cool air no matter what the temp setting or what

>>     buttons were pressed.  Driving speed was 75-85 (hey this is CA). 

>>     As soon as I stopped at a light, the air blew HOT.  The next day

>>     I tried a variation...drove the car until warm, pulled over and

>>     waited to see if it blew hot air.  Air only remained mildly

>>     cool.  As soon as I started driving, it blew hot.  I turned down

>>     the temp until it blew cold and then turned up the temp...only

>>     got mildly warm.  At the same stop light as the previous day, it

>>     blew hot.  560SEC has around 165k miles on it.  Does this sound

>>     like a monovalve problem?

>>      

>>     btw..saw a great license plate on a new MBZ when in LA earlier

>>     this week...hys2pid..maybe it was hys2upid...I was dodging

>>     traffic when I saw it

>>      

>>     Tom Oelsner

>>     ------------------------------------------------------------------------

>>

>>     The MB Coupes Website!

>>     W126 SEC Mailing List

>>     Postings remain property of MB Coupes, L.L.C.

>

> ------------------------------------------------------------------------

>

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