Defrost on my 1984 3/4 ton 4x4 suburban does not work but there is vacuum...

[84burban]

I am fairly certain that there is vacuum connected to the dash controller in the cab. The heat blows hot and strong and it will switch through all the selections but defrost. Is it possible that there are multiple connections and one of them is disconnected? I don't have time to rip into it this second... Just seeing if there is anyone out there who has had this experience. This is my daily colorado driver so it is missed.. Thank you!

[82silverado]

I had a similar problem. Defrost would not blow but it would also still blow out A/C vents when in the heat mode. Took the cover off of the vent system at the bottom and sure enough it was the air recirculating valve rod link. A small plastic piece that costs about five dollars. This also prevented it from closing all the way so it would blow out defrost.

[Captkaos]

It is possible that one is disconnected or a rod it not on or the hose has a hole/worn

Chris Lucas
73-87chevytrucks.com
squarebody.biz

[84burban]

Hey Guys, thank you for the response! I have time today to get into it and will be checking everything out. I will post what I find. Thank you!
 

[North Central Ohio]

I had the same issue w my defrost last yr and it was the same fix as 82silverado