ECC system switches abruptly from cold air to warm air, when temperature setting is increased from 78 F to 80 F

[jreed]

I am wondering if anybody else has experienced the same behavior from the ECC electronic climate control system on their 850. Mine is a 1997 850, and the system works as expected on hot days when it is set to any temperature up to and including 78F, but if you increase it to 80 F on either the driver side or the passenger side, the fan speed increases suddenly and warm here begins to blow out of the center vent, depending on if you turned the drivers temperature control or the passengers temperature control. If you turn the temperature knob back down to 78F, the fan slows down and cold air begins blowing again out of the vent.
I recently read the codes and got 211 and 212, which are for malfunctions in the damper motors on the driver and passenger side. I am wondering if I need to repair or replace the dampers I wanted to check here if anybody else has experienced this behavior, and if so what was the cause. Thanks

[scot850]

Does it do this no matter what the external temp is?

Neil.

[jreed]

Thanks for asking... great question! It does it during the summer.... The system works fine during the winter and does the sudden switch from cold to hot during hot days. We observed it yesterday when the exterior temperature was 82-86 F.

[scot850]

Could it simply be the intake air to the system is just hitting a threshold flipping the system from heating to AC cooling? There is the small intake temp sensor just after the fan motor measuring obviously the ambient outside air temp. Maybe it is flaky? Does your intake air have the modification with the cabin air filter?

Neil.

[jreed]

Thanks for the follow up questions.... really appreciate the input. The car does have the cabin air intake filter installed and there is a newish filter that I installed about 4-6 months ago. I will check and measure the intake temperature sensor to see if there's anything going on there. Thanks again!