DEFROST PROBLEMS

[LIZARDKING]

We got a new guy at work. I see him driving up in a really nice 92 SHO. We get to talking and he tells me that for over a year he has had no defrost. I showed him how to run the EATC self test and it shows no codes. Everything works except defrost. When defrost is turned on it blows out of the dash vents. Any idea's? He is not online but I will SHO him the way.

 

[Slo-Sho]

Maybe the mechanical linkage for the blend door actuator??

 

[projectSHO89]

The panel-defrost air door is not being switched, but is stuck in the panel position. The door is controlled by a vacuum motor which gets its vaucuum supply from either the EATC or the manual ****.

It is supposed to deault to the DEFROST position when there is no vacuum applied.

My guess is that it either has vacuum applied all the time due to a failure of the EATC or the motor has failed and has stuck in the panel position.

The motor is mounted vertically on the left side of the AC plenum chamber, roughly above the gas pedal. I'll stick my head under there later and see if it's visible or accessible. The 89 Helms says to remove the instrument panel to access it for replacement, so I'm not sure it will be easy to reach.

Steve