All this talk about Harrison heaters made me want to post tis up. It might be useful to someone in the future.

Restoration tips:

I don't know how many people actually know this but there should be rubber grommets between the firewall and the heater core tub brace on the back of the heater. The left is an original and the right is what I replaced them with.



What was left of my original decal on my '53.



Modifications:

My heater had a defroster duct port which I wanted to use with an original style defroster duct. But I also wanted it to work more efficiently.



So I made some doors that I can open and close for the other two ports.







And after some paint and a custom Willys plaque, it is ready to go!





Defroster hose routing. I am not sure of how it would have been routed from the factory, but this way made sense to me.







Installing a Harrison in your original body:

My '49 never had a heater installed, but I wanted one for the cold months. The rust pile I mentioned earlier has just the right amount of patina and original paint for it. I had also collect enough original parts to install it.



It still had the three original knockouts for it.



On the inside of the firewall, you have to take two cage nuts out. The very top one for the passenger side bracket for the air cleaner and the very bottom on for the drivers side bracket for the air cleaner. I peeled the cage back and beat it flat with a hammer.





And then you get some nice paint samples!



Then you can maneuver the heater into place. I had to cut a 1/2" off the tubes to get it to fit.



Then under the dash, there should be a hole for the original switch.



And then after a little wiring and plumbing, you're all done! On an engine that never had a heater, there should be a pipe plug on the back of the head and another one on the pump. I had to heat mine to get them out.

Thanks John. I saw the bulletin on the defroster on the 3b page. I'd still like to know what the original hose would have been made out of.

Any chance you could show us the heater hose routing and connections, would this be appropriate here in the post or should it be somewhere else? Either way I could use some help, Thanks...

Here is where they connect on the engine.

I wanted to throw in some additional items you may come across if you find a Harrison in your Willys…or plan to add one on.

L-134 engines are interchangeable between many Willys Jeeps.  It’s common to NOT have the original 3A engine in your Willys.  

Early L-134 military heads were not generally set up for heaters.  You may not find a plug at the back of your engine head….




You can drill and tap this to add the correct heater hose attachment, but it would require pulling the header or possibly the engine. That’s a lot of work.  

This was the modification I found on my GPW engine (the Ford version of the L-134) This was a somewhat common approach when adding the Harrison heater to a military head.





All other connection and installation points are the same as described above.  Looks like I matched Ryan’s connection at the water pump.

This is another detail you might find on a Harrison installation. This is a heater hose bracket.  It was mounted to the passenger fender…

Thanks guys one question, on the water pump attachment does either side put you in front of or after the thermostat?

This is a very interesting thread to me.  I also acquired a Harrison Heater that needs restoring and, as with many things, more information is good! 

From garage gnome:
Quote:


I have never seen nor heard of any surviving documentation on these heaters.  I've been fooled before thinking I was looking at original when it turned out to be a PO addition from 40 years earlier.  This grommet is interesting - and I like it.  It would obviously help isolate vibration.   Where did you get the replacements from?

From Ryan_M:
Quote:


I don't have a Parts Manual (PM) covering the 3A but wonder if y'all could check to see if the fitting matches what's listed for the 3B:

GROUP 35-21 - HEATER AND DEFROSTER
664971     1 Elbow, heater, 45 degrees

I polled some 3B members that had an original heater and apparently that 45 degree fitting was attached to the pump.  Mine originally had a straight fitting but I like the idea of the 45 degree fitting as it seems to clear other components with room to spare.

From athawk11:
Quote:


This one also stumped me at first sighting over on the vernco.com site.  Again, checking the 3B owner's, they showed the same bracket:

669733     1 Bracket, support, hose

Now knowing that the 2A, 3A and 3B used this bracket I'd assume it's the same. 

This is not a Harrison heater but it was installed on the drivers side of my 543B. There are 3 little doors on the front and sides to control air flow. It's small but works great.

Left of steering wheel.

From passenger side.