Exhaust Fan runs whether door open or closed when 1st plugged in

GE Profile Microwave Oven PVM1870DM3BB replaced Magnetron, Diode, Capacitor, all 3 door switches, Thermal Switch.

Microwave heats and shuts off normally but Exhaust fan constantly runs and the fan symbol on the display is indicating it is on.

When I disconnect the microwave and then plug the power cord into the A/C socket, the display comes on and then the exhaust fan comes on low and stays on all the time whether I heat up something or not.

I set the clock to a time and then microwave shows time in display. Next I put a cup of water to heat for 30 seconds and it counts down to 0 then beeps and shuts the magnetron off but fan ALWAYS stays on. I went into OPTIONS and selected normal and one other time slowest fan speed but the exhaust fan continues to run.

I do not know where the exhaust thermostat is. I replaced a thermal Switch which was on the lower right vertical frame just to the right of the fan that cools the large transformer.

I have no readable schematic of the parts and now at my wits end. The microwave works perfectly but for the EXHAUST RUNNING ALL THE TIME WHETHER IS WAS JUST PLUGGED INTO THE a/c POWER WALL OR IT IS JUST STANDING THERE IN NO HEATING MODE OR IN HEATING MODE.

THANK YOU KINDLY FOR ANY INFORMATION/LEAD YOU MIGHT SUGGEST