After the AC11 finally completely quit (no hot water for defrost), and this after the PO replaced the whole works with fancy new stuff just a few years ago, after which it quickly defaulted to defrost only, I finally took the plunge today and ripped out my ACII and simply plugged the coolant lines right into the heat exchanger. Living here in the Salish Sea, it is never too hot (at least not for someone who grew up in SoCal) and so AC was disconnected long ago. And, it is never bitter cold here. So the only function I really need is to defrost, and that is what she now does admirably.

On this and other forums I've read some question as to whether the little electric circulating pump is necessary for hot air when idling, and let me add my voice to those who speak from experience saying it is not. My defrost cranks out the heat at idle just as it does other times.

For anyone else looking to do this, even for a temporary fix, let me tell you that it does not cost a penny, as you can reuse the coolant line from near the firewall to connect the pipes near the front of the engine. One of them is long enough, and you can tell.

I suspect this fix may be permanent on my car, as all I will ever need is defrost, but if I ever feel like I have $ burning a hole in my pocket I may install the manual valve in the line to control the flow of hot water. Doubt I would bother.

What I love most, perhaps, about my 300D is the elegant simplicity of the motor, and it is nice to have ripped out that monstrous AC11 and to have removed an incongruous complexity from an otherwise bombproof and simple vehicle.

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Where there's a will there's a way
1978 300D