Defroster Won't Work

[cornbinder 84]

Well it's getting colder of the mornings, and I turned my defroster on this morning and it won't work. All of the air comes out the front vents. I have a 1983 service manual from Ford (truck is an 85) and went through the check list and every thing seems to be working correctly with the proper amount of vacum. According to the shop manual on defrost, neither of the two vacum motors should have vacum on them and they don't. I took out the radio and the glove box so I could get at the motors, and both seem to be working properly. I had to quit working on it because it got dark and my shop is full right now (1970 Chevelle and 1965 Mustang doing full restos on both but neither are mine). Do you guys have any ideas on what could be wrong?

Thanks,
Jack

 

[zpd307]

defrost is the default setting with no vacuum applied. i am not familiar with the internals, but is some sort of door sticking that would direct the air to the defrost.

 

[Sycostang67]

A real common occurence on the 80-86 trucks is the blend door hinge likes to break. When it breaks, you lose the defrost default. Some people have been able to use small hinges to make the door functional again. Since the A/C in my 85 didn't work, I removed the front half of the heater box that holds the ducting for the dash vents and just taped a piece of cardboard over the hole. This still allowed me to choose between the defrost and floor heat functions.

 

[Diesel Max]

defrost is the default setting with no vacuum applied. i am not familiar with the internals, but is some sort of door sticking that would direct the air to the defrost.

That would be my guess, if there are no vaccum leaks............

 

[zpd307]

but even with vacuum leaks, it would be on defrost as default. if th eproblem was stuck on defrost, a vacuum leak would be more feasible.

 

[Dsl_Dog_Treat]

I'm leaning towards a stuck or broken blend dorr as well.
Quite posibly a pen or some type of foreign object may have made it's way to the door keeping it open.

My dad was terrible for sticking pens in the vents to hold em so they wouldn't get lost.

 

[riphip]

You can still get the blend door from Ford. I'll check the numbers on my boxes and post back later. I think they are $30-50 each. They were used late '70s thru '96 or '97.

Rick

 

[cornbinder 84]

Thanks guys.

I was leaning to a broken door. The vacum motor that switches between defrost and the front vents moves, but nothing changes. I was hoping it wasn't a broken door because I didn't want to remove the heater box to fix it. The truck does have all of the a.c. stuff in place even though it doesn't work, so it looks like it will be a bear to get out. Anyone have any tips on an easy fix?

Thanks,

Jack

 

[riphip]

Part # & description is: EOTZ-18A361-A SEAL & DOOR ASSY - HT

On my part box it is described as 'Control'

Powerstrokeshop.com has it for $30 + shipping

Rick

 

[Sycostang67]

It's not to difficult to get to. Remove the top of the dash and the glovebox door. From there and under the dash to can reach all the screws to remove the front half of the heater box. Then you can decide to fix the door or band-aid the problem like I did. There is a large opening between the front half you remove and the back half attached to the firewall. If you just cover the opening with something( I used cardboard and double sided tape) you will still have your defrost and floor heat options back. If you want everything back, then you will need to find a way to fix the door.

 

[cornbinder 84]

Thanks Sycostang. I guess I will tear into it this weekend. I noticed you've got a '67 Mustang. I just finished one up for a customer last summer. It turned out pretty good, but I didn't like the paint he chose. It was really hard to spray because it had a lot of metallic in it. Altough the picture does not show it very well.

Thanks,

Jack

 

[Sycostang67]

That looks pretty good, although I cant say I've ever seen that color before. Mines still in primer, I'm trading a truck to a friend to paint my car for me. The problem is he's still looking for a job to be able to afford the paint.

 

[Chipped]

Hey guys, i am brand new to forum here, like 5 mins ago i joined. So i dont think i am posting this in right place. But i will give it a go anyways, since i am having a similar problem.
I have a 2002 Ford F250 7.3L superduty XLT. My defrost does not work either, i have been doing some research on it, and i see people saying could be the vacuum, could be the flapper door.
Checked vacuum, looks like it works good, i have seen that people are saying, that the default position if vacuum is out is "defrost" position. This not being the case with my truck. I have accessed the flapper door, through behind the glove box as well. seems to go through all functions when u move the switch, but when ever u go to defrost, it blows out the front panel vents, and when u unhook the vacuum thinking it will go to default defrost, it still comes out the front panel vents. all other switch positions work, AC, floor, etc. I then thought maybe its the selector switch, ordered a new one for $30, and crossed my fingers...Got it today, same thing still happens. I have been unable to find any vacuum leaks, when i go to move the flapper by hand, thinking that maybe its just not getting set to the right position, i can not get air to come out of defrost no matter where i manually move the flapper, can get it to come out everywhewre else its supposed to, just NO defrost! . Gets cold where i live, NEED HELP, lol
Thanks!