Thanks Bill
I have figured out that while I have become competant at the basic work on these things I have had three different versions and the requirements get mixed up. Funny that that info should be in the 'Installation ' manual as opposed to the service manual. In any case it would cost over $300. to drain and fill the system so if it isnt reccomended then I will think on it a little more. One heat exchanger that went out is under the kitchen cabinet and you have to crawl in through a drawer opening. When that is done it may make up my mind for me ...
Eric,
So what you are telling me is that the new cap I put on just before losing the first heat exchanger might be the problem? I hate it when that happens! Wouldn't surprise me though LOL!
Will try the acid test hopefully before one of the tougher ones goes out.