Our 2003 Honda Accord EX-V6 with Nav started having a problem with the heating/air conditioning a couple of weeks ago. It started after the last service at the Honda dealer. We also had a full detail done on the car about the same time. Something may have been disturbed during one of these actions.

The automatic system tries to maintain the temperature, but there is no blending. It goes from freezing cold to very hot then back again. It just keeps doing this cycle over and over. It appears to me that there is a problem in the air mix motor circuit. There is plenty of heating and cooling capacity. It's just not being controlled. How can I test the system to see if there is a problem in the air mix motor circuit? Or maybe something else?