Sounds like you are getting no heat at all, if that is the case then it sounds like the monovalve has failed in closed position. i.e. not letting hot water into the heater core. These are designed to fail in the open mode and deliver heat all the time. It is located just towards the drivers side, just beyond the battery.in the area between the firewalls. It is the square flat metal with the round piece sticking up through it. with an electrical connection.

Now disconnect the battery.

Unplug the mono valve and see if it lets hot water into the heater core. you will get heat but you have to be moving to force the heat into the car without the fan. you can check the pins(one hot one ground) and listen to hear the valve working. if not it's dead. if it's dead leave it unplugged to let water into your heater core.

Next check the aux water pump. the connection for that is right beside the battery clipped to the firewall just before the Mono valve. Unplug it and check the male connector pins(one power, one ground) to see if your Aux water pump is alive or dead. If it's dead just leave it unplugged for now. It just helps maintain pressure when you are in traffic.

Now if either or both are dead, chances are that they have fried the CCU.
Do a search in the DIY for Climate Control. When eithr of the above seize or fail they can burn through the traces on the circuit board of the CCU.

To remove the CCU you have to disassemble the dash in the console. First remove the ashtray, then the ashtray frame(two screws in the bottom of the frame. Remove the radio, then you will see two screws above where the radio was remove these. Remove the switches above the CCU. Gently remove the wood and plastic cover, there are two clips that hold the frame to the CCU. Loosen the two bolts holding in the CCU. pull the ccu torwards you. disconnect the 12 pin plugs from both sides, disconnect the lights from their receptacles. There it is in your hands.
Now go to the DIY and search for climate control and how to fix it.

To check the fan motor remove the glove box(remove the plastic pins and keepers and save. then remove the light, remove the box. in front of you on the left is a vertical plug attached to the fan/heater box. unplug the fan and check the pins(one hot One ground to see if the fan is dead, if not then the problem lies in the CCU that you have taken out.

Hope this helps.

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1986 Euro 500SEC "RUF" 9:1CR, "Rose"
1985 Euro 500SEC Cabriolet AMG Widebody
1982 Euro 500SEL "Blue"
2001 Texas Heeler (Aussie/Queensland X) "Sulphie",
2012 Queensland Red Heeler "Squeak"
Best dogs I've ever had.