Fresh air vent door not opening

[Flyer58]

No AC in my YJ and when I slide the top lever to the VENT position I found the vent door doesn't open.

The FSM shows that door is actuated by a vacuum motor and cable. Two cables for the Defrost/Heat and Cool/Warm are working properly now that I pop riveted the small bracket back onto the air plenum.

I think I see the vacuum motor way up over the radio but it's buried deep inside. I know I have a good vacuum source coming in through the firewall.

The FSM says just remove the glove box and assist handle which makes it sound like I'm opening a Tupperware lid. Probably their way of saying pull the whole dash off.

Is that what I need to do? Looks like the instrument cluster has to come out to check the vacuum motor switch. Maybe a hose got bumped off.

Not looking forward to this for a little door that probably hasn't moved in 20 years.

 

[machoheadgames]

The big flap on the lower right hand side is cable operated only. By big flap, I mean the vent in front of passenger knees below glove box. The air supply that gets to it is enabled by a vacuum flap up top by the cowl. I see no reason why you need to get to that one unless you confirm that you don’t have airflow once you get the big flap open.

There is a cable from the heater control that runs up to the plenum way up in the dash next to the brake pedal assembly that dumps in vent air for the driver. That same cable runs over to the passenger side to pull the big passenger vent flap open. Those two flaps only open on vent mode. If you follow the cable from the heater control, you’ll find a threaded adjuster. Screwing that in or out will change how much the cable opens the flaps. That was part of my problem. If the cable isn’t adjusted right, it can bind the flaps and they won’t open. My passenger vent flap didn’t work for a year or two until I found that adjuster and fixed it. I can take a pic tomorrow if needed.

Vent mode basically opens the flap up high next to the brake pedal assembly for the driver, and opens the vacuum flap in the passenger upper cowl and also opens the big flap so that the air going through the vacuum motor makes it out the vent to the passengers. The drivers flap is only open in VENT mode, the vacuum motor is open in any mode but OFF, and the passenger vent is open in VENT mode only.

 

[Flyer58]

Thanks I'll get on my back again tomorrow and have a better look up there for the cables. No pic needed yet since now I know what to look for. The big vent door on the passenger side is closed and I don't see the cable moving at all. I tried to follow it but got lost somewhere up high inside.

I think I have airflow in the heat mode so I think the vacuum must be working but I don't have door uppers with my hardtop so I really haven't verified it. It get pretty windy inside.

This is the door (right side) that's not opening so we are talking about the same one. I appreciate the help and this gives me a clear understanding for what to look for.

Cheers.

 

[machoheadgames]

Thanks I'll get on my back again tomorrow and have a better look up there for the cables. No pic needed yet since now I know what to look for. The big vent door on the passenger side is closed and I don't see the cable moving at all. I tried to follow it but got lost somewhere up high inside.

I think I have airflow in the heat mode so I think the vacuum must be working but I don't have door uppers with my hardtop so I really haven't verified it. It get pretty windy inside.

This is the door (right side) that's not opening so we are talking about the same one. I appreciate the help and this gives me a clear understanding for what to look for.

Cheers.

View attachment 118726

Yeah, the cable that operates that door splits off of the cable that operates the door way up high on the drivers side. If you have AC it may be hard to get to but the threaded adjuster might fix your issue. If not, you probably have some rust or other stickiness on the hinge mechanism and may need to pull the heater box to fix it.

If you have heat on head mode, then you’re probably good on the vac motor operating.

 

[Flyer58]

Wow, I came just short of doing a Linda Blair in The Exorcist maneuver trying to crawl under the steering wheel and look up above the brake pedals. Looking any further is not gonna happen without removing the driver's seat first. I did get a quick glance at the cable up there and both that one and the one by the passenger's knees do not even hint at moving when the slide lever is brought over to the Vent position. I see the plenum air divider down low moving when I slide from Off / Def / Heat but nothing after.

Also the Cool/warm slide controls another lever down low without any problem.

Time for an Ibuprofen

I'll follow up when I can get back under there but it won't be for a week or so.

Thanks.

 

[Flyer58]

Problem solved - maybe.

I pulled out the heater control panel enough to see the problem. The cable loop had come off the control lever pin and once I reinstalled it in place it works ok. It looks like the pins are wearing so I'm guessing this will happen again or it was bumped off when someone was getting their hands up in there to wire some lights or radio.

 

[machoheadgames]

There ya go. If you continue to have trouble with it maybe an eBay replacement would work or you could maybe rig something up with tape. Those always have been pretty hard for me to remove, I'm guessing it was knocked off by accident or maybe even disconnected at one point and never put back.