Red and blue connect together, Try a PD 4600 that mounts where the Magnetek's electronics are now, save a few bucks.
Go to www.bestconverter.com and scroll down on the left side to EXTRA INFO
There you will find a link to
Magnetek/Parallax to PDI or PMAnd there you will find all your answeers. How to do it.
Instructions for using a 4600 or 9200 are the same save for you don't need to remove the existing electronics (just disconnect) with the 9200
An even easier way
Hook the 9200 to the house side of the battery disconnect switch and simply disconnect the 120 volt power to the Magnetek, an internal relay will bridge the red and blue so long as the Magnetek elecctronics does not have power.