If you plan to creat a new system you will obviously have to know how it works, to establish such. While the learning is possible the doing is real unlikely, so instead learn how to remove the heat from the defrost position of your current system. Out of hundreds of activities that take place in the system you would have to recreate, only one creats the heat associated with defrost. Toggle it.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician