Slow down a little. You had said earlier that you still didn't have heat with the monovalve disconnected. The ccu can only turn the monovalve on or off. If it is unhooked, it is off. Off = heat. You now have heat with the modified valve, so that means the valve is bad. You can put in a new ccu if you like but I don't think you need it. Never replace parts until you prove they are bad. You have proved the valve is/was bad. The new ccu may not be as good as the one in there now. Fix/replace the valve and go from there.

Paul

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84 500 SEL (307,xxx miles)