Does anybody have an exploded view of the complete mono valve assembly? Looking down inside the assembly there appears to be a plastic ball is this the device that controls the hot water flow when the solenoid has no voltage, if so how can you tell if any hot water is getting past the ball on full cold position on climate control? aux pump is working in heat mode and I have the proper voltage at solenoid, but vent temp at 40 degrees ambient is about 130 degrees in winter lower with colder ambient temps engine temp runs at 85-90c. I have replaced the plunger assembly. Thanks for any help

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84 300 Turbo / 320,000
96 E300 D / 55,000

If you search you will find that there has been a lot of discussion over the last few months about the monovalve function, but moreover the issues with the rebuild kits.

Based on what I've read here, it sounds like MTC rebuild kits are running at least 50 percent failure rate right out of the box (they were never long-lived vs. the OE Bosch, but didn't have many instant failures when installed).

There has also been discussion about pulling the monovalve assembly off the car and soaking it in CLR or a similar product overnight to ensure it's working properly.

Right now the rebuild kit issue is really big as the Bosch part is no longer available.

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

The ball float prevents hot coolant flow into the cabin heater core when engine is off. Have you put your hands on the heater hoses into and out of the firewall to feel what temps they're at? I posted a pic of the monovalve internals recently. Do a search and you will find it.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked