Thanks for the info on the vinegar flush. Vinegar is cheap and environmentally friendly. Our water is hard here in AZ. I use vinegar to clean hard water deposits and it works quite well.

 

How much crud did you see with the vinegar flush, number9?

 

 

Most of the crude came out with the the initial water flushing. I found a few bit's and pieces at the top of the thermostat the vinegar must have helped dislodged from somewhere. I didn't use a pan to inspect for debris or dissolved deposits when draining the vinegar mix.
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