ive been working on and off(between my competitors) on a J4sff-40b..
brand new out of the box i replaced the controller under warranty..a couple years later im called and see someone replaced a compressor but now the system is hot (its a freezer) evap fans were running and nothing else..
called cold/tech they suggested i replace the controller again, and i did.
went to 0 and i bailed..next day customer says its hot..i come back call cold/tech we go over the digital setting, everything is good..i looked at it yesterday and its still good..tonight i get a call...warm 40*...MOnday ill go back in the a.m..
any of you guys work on these things??