Harrison Heater

[pfarber]

There are few options for getting heat into a CCKW. One option is a 'Harrison Heater'. BUT most of the heaters are not NOS, nor are they WWII era production.

Take this image of a Harrison heater installed in an unnamed CCKW:

wrongcckwheater.jpg (6.22 KiB) Viewed 13543 times

Note the boss (or hump) on the far right side, at the point where rounded metal transitions into the flat portion (near the 'point' of the triangle).

Now, compare to this:

cjheater.jpg (20.12 KiB) Viewed 13543 times

So how can you tell the difference between a wartime heater designed for a CCKW? The details are in the mounting hardware on the BACK of the heater.

Here is a pic of the heater mounting points from the assembly manual:

And compare with a 'generic' or CJ mounted heater:

HarrisonHeaterRear.JPG (41.33 KiB) Viewed 13543 times

There are many differences, but the big ones are:
The length of the mounts are longer for the CJ than the CCKW (note the CJ bottom bracket is large enough to have reinforcing ribs stamped in them for stiffness).
The position of the mounting bolts is difference.
The shape of the mounting brackets are different.
The motor shaft fan mount screw is much longer on the CCKW one than the CJ one.

The install TM YT-4336 is available from several sources.. so if you want to add one to your truck, it has all the parts listed (and photographed). The install TM is a gold mine of CCKW info... lots of rare engine bay shots.

[retro-roco]

Paul,

the differences you mention are all great things to look for. Another very easy to spot difference is shape of the heater core pipes as they exit the heater. The ones for CCKW/Chevy heater are straight, while the CJ heater pipes are bent at a very noticeable angle toward the heater fan.

[pfarber]

I found a place that has the install TM and have it ordered.. should be here shortly.

There only thing I want to confirm is that raised boss from the second photo. I've read that its supposed to be for a lever that controls an adjustable baffle. But I could not confirm it from what I could find.

The TM was only $25, but the engine bay shots (like the one I posted here: viewtopic.php?f=22&t=639 ) make the TM twice a valuable.

I plan to get a Harrison Heater and then 'revert' it to the TM's specs.

The biggest flaw I see in the design is that it does not use a squirrel cage blower, but a 4 bladed fan. The squirrel cage was used on heaters of the period, just not this specific Harrison one.

[retro-roco]

Paul,

I have a copy of the manual you mention (YT-4336). The only photo in the manual which actually shows the front of the heater does NOT appear to have the small circular boss visible in the pics above. I have a take-off heater, which has all of the characteristics of a CCKW heater (straight heater core pipes, short back mounting plates, etc.) and signs of OD paint under the existing top coat; but does have the raised boss. It is also put together with clutch head screws, like the ones used in my Chevy truck cab. Maybe the boss is a later issue feature??

[pfarber]

I want to say that it is, but until I have the TM to post the image of a period production one I have no proof. And the reason for this section is to weed out wartime/post war items.. and to do effectively a copious amount of documentation is required.

Everything I have read points to the boss being there for an accessory item (a damper for the passenger side vent)... but I have not found a pic of one with the lever.

[retro-roco]

You mean something like this one??

[pfarber]

Wow you're good. It looks like that's the reason for the boss.

Here are some additional photos of a NOS (out of the box) Harrison heater... I did ask for a frontal shot, but you can clearly see the items that were already pointed out:

Small lower bracket with not stamped rib, straight pipes, mounting bolt is near the edge, not in the middle of the thinner section.

It also looks like the metal is parkerized... the fan motor is OD, but the rest of the steel looks like zinc park.

[retro-roco]

It also looks like the metal is parkerized... the fan motor is OD, but the rest of the steel looks like zinc park.

Actually it's two different colors of OD. The fan motor is slightly lighter and also has a slightly higher amount of gloss (or less drab, depending on how you look at it).

[pfarber]

I just got the install TM today and its pretty much settled... that boss should NOT be a WWII production Harrison Heater installed in a CCKW.

I'll can the image in later on.

[retro-roco]

Really, based one one picture in a manual? I agree that it indicates that a no boss heater IS correct, but without knowing when the boss was added, how can you so DEFINITIVELY state that one with a boss is wrong?

[pfarber]

Because of the totality of the differences.

Show me a heater with a boss, straight heater core pipes, shallow mounting brackets with no ribs and the mounting bolt near the flange vs in the center of the box.

Add to that we KNOW the reason for boss was for dampers used in a 'deluxe' model and has no use on the standard version (military versions of commercial units rarely have deluxe features).

So, with everything posted so far, is there any evidence (other than the first photo, which is not usable as it is of a restored truck, not an original) that there SHOULD be a raised boss?

With everything posted so far is there any evidence that points to any other conclusion?

If there are any other sources to back the claim that the boss SHOULD be there I will reexamine the statement. But I think its clear that it should not be there, subject to revision if additional evidence pro/con is discovered.

[retro-roco]

...we KNOW the reason for boss was for dampers used in a 'deluxe' model and has no use on the standard version (military versions of commercial units rarely have deluxe features).

Paul that argument is not logical. The boss could ONLY be used for a damper on a deluxe model if there was a hole hunched in the boss to install the damper... The kit that Joe bought (I think its one I put him onto) did not have a hole punched in the boss, and neither does the used heater I have out in my garage. My heater has ALL of the characteristics that you've described as pertaining to these heaters, but has the raised boss.

I am not suggesting that either is categorically correct, but rather that we simply don't know enough to determine that, based on ONE photo. That same manual also shows what appears to be a battery and heater mounted to the firewall. I am not a CCKW expert, and really am not familiar with that arrangement, but would never think about declaring that that was the only correct location...

I suspect that your naming of the above photo and this declaration perhaps have more to do with your disdain for Bendover, and his heater... You actually named the photo before you even had the manual!

[pfarber]

The presence of the actual hole is not a requirement to have the boss itself.

Most likely what happened is post war the heater was deemed good enough to continue into civilian production. So they took the wartime dies and reworked them to a new model WITH the boss. There is no reason to stamp two separate heater bodies so you can have one with dampers and one without. So they simply stamp one body and the basic model is bare, the deluxe model gets the dampers.

Its done all the time.

I stand by my original statement. WWII production heaters are WITHOUT the boss (as per the manual).

Its easy enough to disprove: show another TM with a picture of the heater WITH the boss OR a picture of the heater with the boss with some sort of date for WWII OR a post war heater WITHOUT the boss (and with the other civilian features - bent tubes, large flange etc).

[pfarber]

Last bit of trivia.

The post war part was Harrison Heater model number H441A.

The GMC part number for the complete kit is SSL-1276

The heater itself is GMC-3117868

And yes, if you have one, I am looking

[retro-roco]

Sorry, the only one's Ive ever seen are "post war". I'll let you know if I ever come across one without the boss.