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symplered 08-21-2007 09:54 PM

Mono Valve Location
Does anyone out there have a diagram that shows the location of the mono valve (95 SL 500)? Thanks!

tecqboy 08-21-2007 10:26 PM

Just went through that myself. Right rear of engine compartment. Remove the large black plastic cover ( either 3 or 6 screws ) that butts up against the cowl. Beneith the cover at the very front wall of the compartment is the mono valve and just below it the aux water pump and motor. Also in there are many of the electronic modules and the infamous OVP relay and fuse. You can look up a picture of the mono valve in the buy parts section of this forum.

symplered 08-22-2007 08:46 AM

Thanks tecqboy... I'm assuming that you mean the right side facing the engine. Hopes this stops the hot air flow inside the cabin. This part cost a ridiculus $204 at the MB parts store. They are going for $78 brand new on ebay. Will post results when i replace part....

tecqboy 08-22-2007 11:09 AM

I should have said passanger side of a US car. The valve is normally "open". That means with no power, it passes water. It requires a 12V "signal" from the controller to stop the hot water. The valve opens with the ignition off, so hot water gets to the heater core when you turn off the key. If you come back and restart after a few minutes, you get un-wanted heat until the AC cools the core. If you are in EC mode, especailly on a warm day, it takes a long time for ambient air to cool the core down. I wouldn't assume a bad MONO valve just because you are getting heat when you don't want it. There has been much written on this forum about the HVAC system on this car. You can do a "search". You'll find info on how to clear all the error codes from the controller and check all the temperature sensor values. And finally, realize that it was designed primarily to be run in the AUTO mode at all times. EC is OK for heat in the winter, but poor for non AC fresh cool air in summer. The blend doors run on vacuum and the vacuum motors do fail too.

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