91 SHO Climate control issue.

[WhiteSHO91]

my a/c in my 91 sho does not work, so in the summer I never use the climate control, I just keep it off. but now that were starting to have cooler mornings, im starting to (attempt to) use it. The problem is it will only blow air on the windshield. no matter which zone I select, it blows on defrost. I replaced the climate control unit with a hard button unit out of a 95 Taurus and it didn't change anything.

I had to replace my blend door actuator last winter and if pulling the dash is required to fix this issue, I want to get it done before I really need it. Any place I should start? When I select different zones I don't hear any hissing noises so I wouldn't suspect a vacuum leak.

 

[zoomlater]

Did you check the blower control module, do a search on this forum to check if your issues are similar

 

[WhiteSHO91]

all the blower speeds work fine, but it sounds like I need to check the vacuum lines under the hood. ill do that tomorrow and see what I can find.

 

[rubydist]

defrost is the default position, so if the vacuum lines are broken or the vacuum selector is not functioning, all air will blow to defrost.

 

[WhiteSHO91]

thanks for the help. turned out to be a broken vacuum line where it comes through the firewall. a couple layers of heat shrink and 2 zip ties later its working great!