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My heater blower puts out more air when not running, here's why

110K views 107 replies 56 participants last post by  93YJ4FUN 
#1 ·
I've read about guys with jeeps that bake them out after a couple minutes and was jealous because mine didn't. My heater blower wasn't putting out any air hardly at all while the YJ was running. However, if I just put the key in and turned it without starting it, it blows very hard.

I used the search feature and couldn't find anything that covered this.

After checking voltages and other things, I pulled my hood vent cover off. It was spotless and had zero debris inside. I noticed that the vent intake door was open. When I started the jeep up it closed with the heater control on defrost/heat/vent. When I shut it off the door re-opened. Both intake vent doors are controlled by the vacuum switch attached to the heater controls. It has three ports and two vacuum tubes connected to it.

It turns out my tubes had been plugged into the wrong ports! So when the jeep was off the intake doors were open and when running the vacuum closed the doors so no air was coming in from the hood vent.

As the proud owner of jeep that no longer requires a hooded sweatswirt to stay warm in, I hope this post might help somebody else out.
 
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#27 ·
OK, got it working, here;s how it's supposed to be...


Manifold vac with gate valve connected.. (Suck from manifold pulling on black tube to heater settings switch)

Off...
pass side closed, driver side closed

Def/Heat...
Pass side open, driv side closed

Vent...
Pass side closed, Driv side open

The vac switch assy needs to be tuned just right to activate hwne you hit def/heat from the off pos. The plunger on the switch has a good 1" of leaway on your adjustment. Adjust it so it's plunger-out at the point your switch hits Def. Screw all the dash parts back up.

Make sure you keep the check valve in there as the cab could get gas fumes in it if you don't

Hopefully better heat tomorrow.
 
#30 ·
ctm said:
I'm still not clear on which of the three ports the manifold vac plugs into. On Shenandoah's pic it is plugged into the the port 'on the right'. does it matter? I know it's not the center one, that goes to the air door?
When mine was plugged into the other port, it didn't work correctly. It was trial and error and then looking at a buddies set up to confirm it was correctly installed. The center connection was also disconnected at some point in my trials (until my buddy came by). I put silicone caulk on the green hose to keep it connected.
 
#31 ·
ok now im headed back out to verify that this is what mine does....

i have a great heat now when i had little to none before. but if this can possibly give me more then im going to have to check it out.
 
#32 ·
Also, does anyone have a fix for those little heater cable clips with the tabs that tend to break off? I tried rigging up some nylon clips held by a sheet metal screw but it doesn't work that great. hate to shell out $$ for all new cables and/or a new control box that comes with the cables.
 
#33 ·
go to advanced or autozone and check out there clips they have a bunch of clips in a single isle. should take care of that

as for my vent doors....

my stuff matches everyone elses in function opening and closing when it should.. now tommarrow aint going to do any good for testing
it's supposed to be 70 so richmond yj you'll have to wait till this weekend it always gets cold on the weekend when everyone is off
 
#34 ·
ctm said:
I'm still not clear on which of the three ports the manifold vac plugs into. On Shenandoah's pic it is plugged into the the port 'on the right'. does it matter? I know it's not the center one, that goes to the air door?
The lil rubber connector has 3 holes.. Center for green tube going to flap, inboard one is black, this goes the the vac supply on intake manifold.

Empty Green Black
hole1 hole 2 Hole 3 - Plunger

The black one goes on the plunger side, green one in the middle
 
#35 ·
jeepthg said:
go to advanced or autozone and check out there clips they have a bunch of clips in a single isle. should take care of that

as for my vent doors....

my stuff matches everyone elses in function opening and closing when it should.. now tommarrow aint going to do any good for testing
it's supposed to be 70 so richmond yj you'll have to wait till this weekend it always gets cold on the weekend when everyone is off
Good to hear Bailey, got your voicemail, sorry didn't get it till late though, call ya back tomorrow. Thanks for the help, looks like we have it all working now.

Ernie
 
#37 · (Edited)
Here's the "YJ Heater Guide" for everything you wanted to know about the heater operations... enjoy

-------------------------------------------------------------------------------------------------------------------------------



When your controls are set to off

Your blower motor should not be energized, both vent doors inside your hood intake should be closed
and your vent door inside the cab on your passenger side should be closed



Driver Side-Closed



Passenger Side-Closed



Inside Vent-Closed
 
#38 · (Edited)


When your controls are set to defrost/heat

Your blower motor will now be energized with three speeds, the vent door inside your hood intake on the passenger side only will be open, and the inside vent will be shut



Passenger Side-Open



Driver Side-Closed



Inside Vent-Closed
 
#39 · (Edited)


When your contorls are set to vent

Your blower motor will not be energized, both vent doors inside your hood intake will be open, and the inside vent will be open



Passenger Side-Open



Driver Side-Open



Inside Vent-Open
 
#40 · (Edited)
The vacuum switch attached to the heater control has three ports. The hole closest to the plunger should have the black vacuum line in it. The second hole will have your green line in it. The third hole which is farest away from the plunger is left open.



You may have to tighten the switch itself up where it attaches to the heater control. If not the plunger may not be making contact with the heater switch.

I had to use new screws to get it tight as you can see here, this picture is taken from below the control




When the heater is in the Off position, the plunger should be pushed all the way in like this



Inside the hood vent intake; the passenger side vent is controlled by vacuum, while the driver side is cable controlled. If the black vacuum line is not connected to the switch on the heater control, the passenger side intake vent should remain open at all times.
 
#43 ·
workn4livn said:
I see them fine. Nice job, well done
Well that's weird. 3 different browsers on 3 different workstations and I can't see em at all. Logged in or logged out. But... when I paste the url of the pic in my browser, I see them, then return to thread and I can see the pics I pasted int he browser. So if you don't see the pics, copy.paste the pic URL
 
#44 ·
Richmond 88 YJ said:
Well that's weird. 3 different browsers on 3 different workstations and I can't see em at all. Logged in or logged out. But... when I paste the url of the pic in my browser, I see them, then return to thread and I can see the pics I pasted int he browser. So if you don't see the pics, copy.paste the pic URL
Yea the same thing happened to me. I've had to do the copy/paste thing on other threads too, but rarely. We must have some security setting that stops them at first. What I do is copy and paste them into another web page that I have opened up, and then they miraculously show up on the other web page.

Great job Nitrox. You should submit this to Technical Articles & Write-Ups.
 
#51 ·
After reading this I was curious if mine was correct or not. I don't know if the guy on the assembly line didn't care which way he installed the vacuum valves or what, but mine was aparently backwards too. Switching this around did seem to help the amount of heat in the vehice. Pics follow. I also took a clearer pic of the hook-up of the vacuum lines to the heater.





 
#59 ·
I just checked under my hood, and it's like the first picture, but when I disconnected it to flip around the black tapered side is clearly marked V A C... the stem on the blonde end is also much thinner, so I'm going to say it is already on correctly and it's not meant to be flipped around, and if it worked better for you after you ran it backwards, it's probably defective. I looked under my dash and the vacuum lines are where they're supposed to be. I guess my heater core is clogged after all.
 
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