Peter,

You certainly made it crystal clear why the a/c evaporators in the 124 Models are prone to failure and I haven't heard that kind of talk since I took a course in metallurgy. To better understand how the copper and aluminum connections occur in the 124 evaporator, I searched out a photograph and it quickly became evident.

I also found a photograph of the replacement evaporator you mentioned, that comes "all aluminum". I found both versions being sold under the same part number, with the "copper/aluminum" version less expensive than the "all aluminum" and an uninformed DIY buyer might be inclined to make the mistake of opting for the less expensive version. Hopefully, others reading this thread will make a mental note of this information and check it out.

In further searching, I found a photograph of the model 126 a/c evaporator and it is entirely different in design and is "all aluminum".

Many thanks for educating me on how to go about searching for a refrigerant leak.

Based on the response I received from M.B. Doc it appears that I need to chase a set of R-12 gas tables that will provide information on what the "Hi & Lo" gauge readings should be for different ambient temperatures. This gets a little more complicated considering one of the threads I read where the engine revs have to be factored into the equation (either idle speed or 1500 rpm). Perhaps someone can identify where I could find a chart that would tie all of this together.

William