1992 Defrost always blowing

[skyshadow07]

I'm having an A/C issue on my 92. Unless I put my system in 'floor', it will blow out of what ever area I choose plus defrost no matter what. So if I put it in 'panel' I get that and defrost with the majority going to defrost. I have pulled the unit and smoked all vacuum lines coming from the unit, there are not visible leaks and all lines are attached to the actuators. Any help or suggestions would be appreciated.

 

[Irish Pride]

You need to replace the blower motor controller. What is typically called a resister on most cars. It's under the dash to the left of the blower motor. When it fails the system defaults to defrost. You might notice the blower on in defrost when the unit is turned off too. Another common sign of a failed unit.

-Chad

 

[Devin]

IIRC it is under the stack of connectors and it sticks into the housing.

 

[zoomlater]

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[SHOrod]

You need to replace the blower motor controller. What is typically called a resister on most cars. It's under the dash to the left of the blower motor. When it fails the system defaults to defrost. You might notice the blower on in defrost when the unit is turned off too. Another common sign of a failed unit.

-Chad

Very interesting. I recall years ago when my blower motor controller failed I only had high speed, but I can't remember whether or not the system defaulted to defrost. I know many (maybe even all) vacuum controlled systems will default to defrost as a failsafe, but I hadn't heard before that the blower speed controller on these cars would also cause the system to default to defrost. I'm not sure I'll have much of a chance to take advantage of that knowledge now, but interesting nonetheless.

-Rod

 

[luigisho]

Yes failsafe default is defrost

 

[skyshadow07]

Good info, looking into it.

 

[DNort]

Hello! Sorry to bump this thread.
I am looking at replacing this part myself as mine is bad.
It's fairly easy as it's just 2 bolts and 1 hose. However, my unit looks like it has a spot for 2 hoses coming out But my car only had one hose. Am I missing some sort of hose? My HVAC seemed to work correctly (minus ac, clutch is bad) prior to the blower control module failing.

Edit: It seems that my "missing hose" is designed to be open as some sort of aspirator for the cabin air temperature sensor. Can anyone confirm?

 

[Deathacus]

Hello! Sorry to bump this thread.
I am looking at replacing this part myself as mine is bad.
It's fairly easy as it's just 2 bolts and 1 hose. However, my unit looks like it has a spot for 2 hoses coming out But my car only had one hose. Am I missing some sort of hose? My HVAC seemed to work correctly (minus ac, clutch is bad) prior to the blower control module failing.

Edit: It seems that my "missing hose" is designed to be open as some sort of aspirator for the cabin air temperature sensor. Can anyone confirm?

Yurp, thats exactly what that is for, odd as it seems