You do not have an aspirator motor on the 84 380se. That started in 1986. Your inside temp sensor is hooked up via a rubber hose to a nipple that is on the blower motor housing.

Also, up to 1985 you have an older style CCU. I have never opened up one of these before, but I have opened the one on my 86 300sdl and it has two circuit boards.

I do know on the older CCU units there is no provision for a short in the system anywhere, and then you burn a trace on the CCU board. On 86 and later there is a built in circuit breaker that will trip and put the unit into default ( defroster mode) when something in the system goes wrong.

I would check the resistance of the heater core temp sensor and make sure it is in good shape along with the resistance of the interior temp sensor.

Good Luck
I fought a week long battle with my 86 and I won and it works well now. I replaced the monovalve insert, the center vent pod, and the CCU.

John
86300sdl