I would guess:

#1. a bad mono valve.

Mono valve links thread
http://www.peachparts.com/shopforum/diesel-discussion/281902-mono-valve-links-thread.html#post2514617

#2. A fried ACC Board = no power to the mono valve = maximum heat all the time.
It is possible the mono valve diaphragm has failed since the manual shutoff valve was installed = no heat.

Aux. Water Pump takes out CCU
Aux. Water Pump takes out CCU

Fried ACC Board (picture) due to frozen aux pump?
Fried ACC Board (picture) due to frozen aux pump?

I rebuilt my auxiliary water pump
http://www.peachparts.com/shopforum/general-information/38739-i-rebuilt-my-auxiliary-water-pump.html#post219859

Fixed Auxiliary Water Pump!!
Fixed Auxiliary Water Pump!!





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__________________
ASE Master Mechanic
asemastermechanic@juno.com

Prototype R&D/testing:
Thermal & Aerodynamic System Engineering (TASE) Senior vehicle instrumentation technician.
Noise Vibration and Harshness (NVH).
Dynamometer.
Heat exchanger durability.
HV-A/C Climate Control.
Vehicle build.
Fleet Durability
Technical Quality Auditor.
Automotive Technical Writer

1985 300SD
1983 300D
1984 190D
2003 Volvo V70
2002 Honda Civic

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