HVAC Vents

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Topic author
wyocherokee
Posts: 8
Joined: Wed Jun 09, 2021 12:17 pm

HVAC Vents

Post by wyocherokee » Wed Jun 09, 2021 12:49 pm

Dissecting my new to me 89 GW, i dont have air flow to the vents. Is the blend door easy to get to on these? vacuum hoses all look good, and i replaced a few. i am guessing the door is stuck closed.
89 GW all stock. Custom game carrier and 12v pass through wiring from the PO


letank
Posts: 3379
Joined: Wed Oct 03, 2012 9:16 pm
Location: SF bay area

Re: HVAC Vents

Post by letank » Wed Jun 09, 2021 6:11 pm

if you are talking about AC vent, this is dependent on the AC motor being on, it is basically a recirculation system.

the heater and defrost flappers depend on the vacuum being applied to the control unit and for the heat level, it is the flapper in the engine bay above the heater box.

The 86 and later model are different from the previous years as the control HVAC is a one unit in the middle of the redesigned dash, with the fan speed being on the left side of the instrument cluster.

Check fuse, then vacuum feed to the back of the center module. It is a bit of a pain to check it out. Pulling the bezel of the instrument unit is not hard but you need to be careful to avoid breaking the tabs.

Last time I fixed a non working 86 and later heater system... it was a simple solution, but I forgot what was wrong.
Michel
74 wag (349 Kmiles... parked, next step is a rust free body)
85 Gwag (227 Kmiles... the running test lab)
See Engine bits , Fuel and brake lines, Body work, Trany and TC


89_Wagon
Posts: 28
Joined: Fri Sep 27, 2019 9:24 am

Re: HVAC Vents

Post by 89_Wagon » Thu Jun 10, 2021 8:23 am

Just to add, the vents you see are for the AC. Heat comes from under the dash, towards the firewall... can't see them from the driver's seat. So, if you're testing heat, no air flow will come out of the front vents. I also have an '89 and IIRC the blend door flapper that controls heat/fresh air mix is cable driven. Critters like to make a home in the heater core housing and that will make the flapper door get jammed. You'll notice the HVAC lever on the dash will get stiff.

Can you hear the blower motors humming? FYI, there's 2 of them... one for the heater (visible in the engine bay) and the other is under the dash on he passenger side for the AC unit.


Topic author
wyocherokee
Posts: 8
Joined: Wed Jun 09, 2021 12:17 pm

Re: HVAC Vents

Post by wyocherokee » Thu Jun 10, 2021 9:41 am

letank wrote:
Wed Jun 09, 2021 6:11 pm
if you are talking about AC vent, this is dependent on the AC motor being on, it is basically a recirculation system.

the heater and defrost flappers depend on the vacuum being applied to the control unit and for the heat level, it is the flapper in the engine bay above the heater box.

The 86 and later model are different from the previous years as the control HVAC is a one unit in the middle of the redesigned dash, with the fan speed being on the left side of the instrument cluster.

Check fuse, then vacuum feed to the back of the center module. It is a bit of a pain to check it out. Pulling the bezel of the instrument unit is not hard but you need to be careful to avoid breaking the tabs.

Last time I fixed a non working 86 and later heater system... it was a simple solution, but I forgot what was wrong.
thank you for the information. Im used to dealing with the XJ platform systems, so im trying to learn the fsj system. this gives me a place to start
89 GW all stock. Custom game carrier and 12v pass through wiring from the PO


Topic author
wyocherokee
Posts: 8
Joined: Wed Jun 09, 2021 12:17 pm

Re: HVAC Vents

Post by wyocherokee » Thu Jun 10, 2021 9:44 am

89_Wagon wrote:
Thu Jun 10, 2021 8:23 am
Just to add, the vents you see are for the AC. Heat comes from under the dash, towards the firewall... can't see them from the driver's seat. So, if you're testing heat, no air flow will come out of the front vents. I also have an '89 and IIRC the blend door flapper that controls heat/fresh air mix is cable driven. Critters like to make a home in the heater core housing and that will make the flapper door get jammed. You'll notice the HVAC lever on the dash will get stiff.

Can you hear the blower motors humming? FYI, there's 2 of them... one for the heater (visible in the engine bay) and the other is under the dash on he passenger side for the AC unit.
Yes i can hear a blower going on all fan speeds. i did not know there were two of them. i dont have any flow out of the defrost vents either which leads me to believe a stuck blender door.
89 GW all stock. Custom game carrier and 12v pass through wiring from the PO


letank
Posts: 3379
Joined: Wed Oct 03, 2012 9:16 pm
Location: SF bay area

Re: HVAC Vents

Post by letank » Thu Jun 10, 2021 9:19 pm

wyocherokee wrote:
Wed Jun 09, 2021 12:49 pm
Dissecting my new to me 89 GW, i dont have air flow to the vents. Is the blend door easy to get to on these? vacuum hoses all look good, and i replaced a few. i am guessing the door is stuck closed.
the door by the heater box is cable actuated on top of the heater box inside the engine bay, you can move it by hand... if it is full of leaves, try on high speed and smell for burnt leaves or foliage... :

http://www.ifsja.org/forums/vb/showthread.php?t=151042

Image

or as you said above if no defrost the other flapper for the heater / defroster could be unhooked , it is vacuum controlled, take a peek from the trans tunnel by the firewall... hidden by the AC duct... yes it is tight, you might be able to shine a light to spot the hose for the vacuum motor...
Michel
74 wag (349 Kmiles... parked, next step is a rust free body)
85 Gwag (227 Kmiles... the running test lab)
See Engine bits , Fuel and brake lines, Body work, Trany and TC


Topic author
wyocherokee
Posts: 8
Joined: Wed Jun 09, 2021 12:17 pm

Re: HVAC Vents

Post by wyocherokee » Mon Jun 14, 2021 6:44 am

letank wrote:
Thu Jun 10, 2021 9:19 pm
wyocherokee wrote:
Wed Jun 09, 2021 12:49 pm
Dissecting my new to me 89 GW, i dont have air flow to the vents. Is the blend door easy to get to on these? vacuum hoses all look good, and i replaced a few. i am guessing the door is stuck closed.
the door by the heater box is cable actuated on top of the heater box inside the engine bay, you can move it by hand... if it is full of leaves, try on high speed and smell for burnt leaves or foliage... :

http://www.ifsja.org/forums/vb/showthread.php?t=151042


or as you said above if no defrost the other flapper for the heater / defroster could be unhooked , it is vacuum controlled, take a peek from the trans tunnel by the firewall... hidden by the AC duct... yes it is tight, you might be able to shine a light to spot the hose for the vacuum motor...
Awesome thanks
89 GW all stock. Custom game carrier and 12v pass through wiring from the PO

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