Hi all, my truck has a draft. OK in July, not good in Jan. It's an A/C cab. Theres a box under the dash on the passenger side with a big flap. If I push the flap it goes inside the box and and plugs a hole that draws air from under the hood (I suppose). When the flap is pushed closed - no more draft. Alas, the only way it will close is if I hold it closed. How is it supposed to work? The only other way I get no draft is if I have the heater/vent/defrost/AC off.

Help!

Jayson
78 F100

 

Thats your vent your talking about. It should stay closed on its own. You might wanna check to see if a part broke that holds it closed. Good luck!

 

Sounds good. So what holds it closed?

Jayson
78 F100

 

There's a spring inside that overcenters holding it open and closed. If the pivot pins for the door come off it won't hold.
Hope this helps.
Greg
'77 F-250 Camper Special 400ci driver
'76 F-250 Supercab 360ci current project
'71 Mach I 429CJ in storage
'79 F-150 for parts
HONK if you like peace and quiet!

 

My truck is drafty cause its a 79 with doors from a 75 and I may possibly drive little too fast. (honestly officer the tires are so big that my speedometer doesnt move past 10 miles per hour.)

 

Macguyver,

Does that mean I have to take that box out?

 

[updated:LAST EDITED ON 01-11-03 AT 11:44 AM (EST)]I think it would probably be easiest, but I have one out in my garage right now. I'll check this afternoon and see if it's possible to reconnect it with it in.

Edit: Just checked. On the '79 housing I've got out the little tab that the door pivots on, one rivet came loose so the pin on the door came out. The vent door housing unscrews from the heater housing so it shouldnt be too much trouble. Might have to remove the glove box though.
Hope this helps, gotta go
Greg

Re-edit: Of course mine doesn't have AC. Your mileage may vary!

'77 F-250 Camper Special 400ci driver
'76 F-250 Supercab 360ci current project
'71 Mach I 429CJ in storage
'79 F-150 for parts
HONK if you like peace and quiet!

 

Jayson,
Is the draft coming from the door on the lower right side of the heater housing facing the rear? The vacuum pot that opens it should be spring loaded. If the draft stops when the controls are turned to off the doors are working but in any position other than off the system is designed to allow air flow for ventilation. If you don't want that door to open in the winter you could always disconnect and plug the vacuun line to that control pot.
Hope this helps
Greg
'77 F-250 Camper Special 400ci driver
'76 F-250 Supercab 360ci current project
'71 Mach I 429CJ in storage
'79 F-150 for parts
HONK if you like peace and quiet!

 

OK, let me try to explain a little more clearly. It's hard cause I dont know what the official name for all the crap under the dash is but here goes:

1st of all, It's an A/C cab truck. There is a black plastic box on the pass side right above where the passenger's feet would be, below the glovebox, screwed into the firewall. There is a hole in the side of the truck under the dash that lets air in. The door I'm talking about plugs the hole if I push the door in. If It's not pushed in air comes out some openings on the opposite side of the box. Why can I not get this door to plug the hole itself?

If I am not using any of the controls (A/C/heat/hi-lo/defrost) and the lever is in the off position, there is no draft.

I hope I made myself clearer.

Jayson
drafty 78 F100

 

Jayson, there is supposed to be a rubber corrugated flex sleeve(?) that goes between the heater box and the hole in the side of the cab. If this is missing I would think there would be a constant draft. Just something else to try, I guess. I hope you/we can figure this out.
Greg

'77 F-250 Camper Special 400ci driver
'76 F-250 Supercab 360ci current project
'71 Mach I 429CJ in storage
'79 F-150 for parts
HONK if you like peace and quiet!

 

What year truck do you have? Sounds like your talking about your passenger side vent? Is it shaped like an L? and have a small handle on it? If so you are talking about your passenger side fresh air vent. Many people use this in the summer for cool air. I actualy just took mine out to clean out my heater ducts of pine needles that got there from siting for 14 yrs and little mice makeing a home. I would tell you to clean out your heater if you take out this vent, a shop vac is a handy tool. And as for your vent get back to us and tell us if what I described is what your talking about?

 

Well here is what I'm gonna do. 2morrow I will take a picture of it with my digital camera and post it in my gallery. That way I can show everyone w/o confusing them. Need to get this fixed. Ever drive 6 hours w/a coat wrapped around your legs cause you have an ice cold draft hitting your calf? It sucks!

I'll post 2morrow evening. Thanks 4 the help thus far!

Jayson
78 F100

 

Sounds good. A picture is worth a thousand words!

 

OK, It's the last pic in my album. Looking at it from the drivers side of the truck. Remember, No draft of the Heter/vent/A/C etc is in the off position...

Jayson
78 F100

 

OK, I've got it now. I just went out and fired up my '77 (with air) to see how things work. Been sitting 2 months, carb drains down, 2°F outside, crank 2 revs, pump 3 times, crank 2 revs, pump 3 times, crank 2 revs, pump 3 times, fires right up. Gotta love these old trucks. The door you're talking about closes off the outside air when the controls are off. I think it would also recirculate interior air IF it would move when the controls are on, like a Max Air position, but it doesn't. Without taking the heater box apart I don't know why there would be cold air coming in where those wires are unless there is a seal missing. Possibly cold air bypassing the heater core? Is the heat output good otherwise? I think there is supposed to be some sort of foam that seals the box to the firewall. Looks like you will either have to take the box loose or try to stuff some foam in the crack from inside to stop the draft.
Maybe you could reroute the vacuum line to that door through a manual vacuum switch that would apply the door when you want recirculated air? I wouldn't do it full time 'cuz if you only have recirculated air the melted snow will tend to fog the windows.
I don't think the draft is coming from the firewall or it wouldn't quit when you move the door.
Come to think of it, maybe mine has the same problem and I was just blaming it on ventilated sheet metal and poor weatherstripping! Mine doesn't get very toasty when it's cold either, and I only have a 5 minute commute so it doesn't even have a chance to get warm anyway. That's why it's been sitting for 2 months.
I know, long post. I'm sorry. But I hope this helps.
Greg

'77 F-250 Camper Special 400ci driver
'76 F-250 Supercab 360ci current project
'71 Mach I 429CJ in storage
'79 F-150 for parts
huct on foniks wurkt fer me