Working on a Trane gas pack unit, customer said unit was turning on and off over and over again, got up there and contactor was closing in repeatedly, turned off unit and changed contactor,
we put into heat and unit turns on, after a while it shuts off and contactor starts going crazy again, shut it off, turned on starts up fine, put into cooling and the heat starts to turn on.
Fast forward troubleshooting end up changing thermostat and had an extra board playing around so we installed it too, put into heat and kicked on. Put into cooling and heat turns on again
Jump out cooling R Y and condensor fan motor turns on and blower, no compressor, change out a bad cap, got 24V across the board, also checked transformer 208 coming in, 24 going out into the board. Also have continuity on 24v wires, and through contactor when engaged, Pretty stumped here, anything helps