The one in my "new" 300D was stuck -- it will fall closed on the W124, I think just by gravity, when off the car. It will open with flow from the aux pump or water pump, so if it sticks on the solenoid, which is the usual failure, you get no heat at idle and a blast of warm air when you accelerate and the circulation pressure goes up. Since it's normally closed by the solenoid, the usual failure is no heat, but they can stick open too, I suppose. You'd notice that right away.
To test, remove from the car. Valve should be closed. Blow through in the normal direction of flow -- valve should pop full open and produce very little back pressure. You might want to rinse off first. Don't use compressed air, too hard to tell what the opening resistance is. If it won't open all the way or it's got back pressure, replace. They are expensive, and the one from the early W124 chassis isn't as easy to find used as the later ones (they have three hose nipples, I think, not one as the heater core is split and is upflow rather than downflow). Check the auxilliary pump too -- on the gassers it's easy to get to, on the diesels more of a pain but not too bad so long as the fender hasn't been bashed in a foot and a half... Peter _______________________________________ http://www.okiebenz.com For new parts see official list sponsor: http://www.buymbparts.com/ For used parts email [EMAIL PROTECTED] To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
