How does my heater work?

I feel like I read it here before but after a google and forum search I dont quite get it. Can anyone explain how it works so that I can figure out why it isn't working?
Thanks,
Jake

 

They dont work from the factory, near as I can tell.

There are three cable operated doors. One in the cowl plenum that allows fresh air in, or not.
One is a blend door that directs the air through the heater core, or not. The third directs the air either down toward the floor or up through the defroster vents,barely. There is a HI/LOW/OFF switch for the blower.

If you dont have a full hard or soft top and doors, it won't do didley squat even if its working properly.

FYI the cables are made of 90% pure unobtainium

 

Cables are easier to obtain now. Several jeep supply houses now carry them:
http://midwestjeepwillys.com/cj-heater.html
I ordered and installed some from George's Jeep Parts. Mine are USA made. The-jeep-guy.com has them on his website and lists them as USA made. http://the-jeep-guy.com/Heating%20&%20Cooling.htm

 

And then, the hose from the engine attaches to the heater core through the firewall, circulating hot engine coolant through it then back out to the water pump. Your fan blows air through the heater core, which is routed as described above.

I think the most common issue is simply a weak motor fan so you don't really have enough oomph to push the hot air around. But you could have a closed off duct, blocked heater core or hose. It isn't uncommon for some prior owners to just bypass it altogether and run the heater hose from the engine right back to the water pump, but that's probably more for the southern Jeep owners.

 

Here's a guy who made an upgrade on his motor, it's in my plan for next winter

http://www.earlycj5.net/forums/showthread.php?101142-heater-motor-swap-success!

 

This is an excellent thread. My heater switch has three positions (presumably OFF/LOW/HI), but I can't tell any difference between the LOW and HI settings. Any ideas?

 

Hey DREDnot, great photos, but it looks like your missing the drainage hose that runs from the bottom of the cowl through the floorboard (unless you have your cowl blocked off and don't need it).

 

The stock heater isn't bad when it works correctly. I rebuilt mine completely, using new neoprene rubber for the flap doors, cleaning it completely, and boiling out the original heater core. The original core wasn't leaking and was pretty clean, so I re-used it. I used generic cut-to-length cables meant for a manual choke application, which work great. My original fan works perfectly, and pushes enough heat that I almost never need it on high. I recently drove it during a cold snap when it was about 10 degrees and it kept me comfortably warm dressed only in office clothes, not overly bundled up. I have a full softop in good condition.

Now the defroster, on the other hand, is another story. I used only one of the outputs from the heater box and blocked the other, ran a new duct up to the cowl/windshield, and it still just barely blows any air onto the windshield, even on high. I think there's just so much volume in the empty windshield frame that you can't really force out the air at any real velocity. I have the same problem on my Scrambler and it has the much-vaunted GM heater motor upgrade. I just don't really see any way around it unless you run the air up to the windshield in a dedicated small-diameter tube rather than through the windshield frame itself. Some folks have talked about sealing the sides and top of the windshield frame with expanding foam, but I'd be leery of trapping moisture and causing rust.

 

Here it is. They are available new, with the little exit beak, from ATS.

 

Where did you get that floor vent deflector?

 

any yj or earlier to 71 cj...fwiw i put a yj core and blower motor into the 76 with no trouble

 

It was original from the factory, at least on the 74.

 

My 74 has it.