Defrost

[Blazer1AB]

I had to put a heater core in my blazer last weekend and ever since, the defroster hasn't worked. I havent had a lot of time to check it out, but I have basically found out that the door that is behind the middle floor vents doesn't do anything when i switch the control to defrost. I will inspect the vacuum lines tomorrow, but if those are fine, do you think its the little silver diaphram or is something with the actual door broke? I've reached in there with my hand it its feels like its spring loaded- so is this right?

 

[jeeptuff]

Mine does the same thing, no defrost..

 

[nstarry]

there is a another post on here about this everybody says its a vaccum line but they wont tell you wich one it is yet

 

[jeeptuff]

So, which is it?? Come on somebody is holding out on us!!!!

 

[big d]

im guessin its the lil plastic clip on the door that changes the direction of the fan air.the rod is fastened to it and the clip has a sheat metal screw passing thru it. the clip usually brakes right in the middle. its only like a 1.50 or sumpin like that from a g.m. garage. im gonna go pick myself up a couple here pretty soon and fix mine. hope this helps.

 

[GM Man]

I had the same problem on my 78 Jimmy and I found out that if you unplug the vacuum canister on the passenger side firewall, then nothing wants to work. Check this out to see if yours is unplugged.

 

[nstarry]

the controls themselves are activated buy vacum , were is the vacum coming from ? I found the vacum line coming out of the fire wall right buy the heater/ air cowl so I could fix it if i had any idea wear to hook it up to

 

[Muddytazz]

Runs off of a vacuum port off the backside of the intake manifold right between the carb and dist.

the controls themselves are activated buy vacum , were is the vacum coming from ? I found the vacum line coming out of the fire wall right buy the heater/ air cowl so I could fix it if i had any idea wear to hook it up to

 

[nstarry]

thanks man

 

[anjieandjohn]

Big d, you got a part number for that little plastic piece? I took all my ducting out today and guess what, I have that little broke plastic piece. Where did you get it from? Thanks.

 

[big d]

i dont have the pn but its only available from the chevy dealership. just tell em what u need. my dealership has 4 and im buyin em all while they r still available.

 

[anjieandjohn]

Went and got that little plastic piece for the door...cost $1.68 with tax....I put one on and now the heat blows like the dickens...with no blow by to the vents. Now, when I switch from heat to vents or defrost, it doesnt switch. Isnt there a vacuum switch in the ducting somewhere?