I suspect my heater valve ( mono valve ) is at fault as I have had intermittent heat some time remedied only by restarting the car and by keeping temp Wheel on high or highest setting

Though there is a great deal of discussion in various threads regarding the repair 'kit" for the mono valve I have not been able to find any supplier that provides a listing that matches my application 1991 300D 2.5 Turbo Diesel. Is this in fact a unit that the marketplace provides a kit for or should I change the whole unit - Thankyou

I have always been told that the W124 chassis monovalve is not repairable. All you can do is get a used one from a junkyard or a new one from Phil.

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Used (But, not abused) or Brand Spanking New from Bosch/Mercedes.

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'84 300SD sold
124.128