Heater install of M35A3 unit in M35A2

[tcruwithme]

Hey Deucer ~

I just saw this thread, and I am working on the exact same project. I see this is from a year ago. Did you ever finish this project?

I just flipped my air exchanger around and relocated it four inches toward the driver side. I found out that was necessary to get the heater core to fit under the dash on the passenger side. I need to wire up the hi/off/low switch next. If you finished, please let us know how it went and what you learned from it.

 

[Karl kostman]

I put up a post on just about exactly what your doing a couple years ago on my Deuce, if you search my posts it should all be there somewhere, it was a fairly easy way to do it the hardest part was getting the defroster section hooked up to the ducting under the dash and YES that did take some time.
Karl

 

[tcruwithme]

I put up a post on just about exactly what your doing a couple years ago on my Deuce, if you search my posts it should all be there somewhere, it was a fairly easy way to do it the hardest part was getting the defroster section hooked up to the ducting under the dash and YES that did take some time.
Karl

Hey Karl,

I looked back through your posts through 2010 and could not find it. I saw several times when you commented on other similar threads though.

 

[deucer]

Hey Deucer ~

I just saw this thread, and I am working on the exact same project. I see this is from a year ago. Did you ever finish this project?

I just flipped my air exchanger around and relocated it four inches toward the driver side. I found out that was necessary to get the heater core to fit under the dash on the passenger side. I need to wire up the hi/off/low switch next. If you finished, please let us know how it went and what you learned from it.

I did finish it, wasn't too bad overall. I think it depends on what unit you but, mine was a unit made to go in the cab from an A3. The under dash defrost tube was not to bad when I decided to go with the new Napa replacement tubes, much much easier to work with. Also, make sure to clean out the vent hookups if they have been left with no hose hooked up, little insects or creatures can leave a mess or their nest in their. Lastly, the hardest part was properly locating and drilling the holes for the heater hose to go through the firewall, but I wanted it to be as small as possible with grommets so others not as particular or with more experience installing these might not have fretted about it as much. Otherwise it works great, got to use it last winter. For where I live it is plenty hot.

 

[tcruwithme]

I did finish it, wasn't too bad overall. I think it depends on what unit you but, mine was a unit made to go in the cab from an A3. The under dash defrost tube was not to bad when I decided to go with the new Napa replacement tubes, much much easier to work with. Also, make sure to clean out the vent hookups if they have been left with no hose hooked up, little insects or creatures can leave a mess or their nest in their. Lastly, the hardest part was properly locating and drilling the holes for the heater hose to go through the firewall, but I wanted it to be as small as possible with grommets so others not as particular or with more experience installing these might not have fretted about it as much. Otherwise it works great, got to use it last winter. For where I live it is plenty hot.

Thanks for stopping back to the post to comment. I also picked up an exchanger box and heater out of an A3. I'm waiting on a few constant pressure hose clamps, and then I'll be able to finish up. I didn't cut down the size of the heater box like some other SS members did. Instead, I relocated the exchanger box about four inches towards the drive side. That seemed to give it enough room. I see that when I got my truck, the heater hoses were not hooked up correctly. The heater return line is hooked up by the thermostat rather than down by the water pump housing - like it is supposed to be. You certainly learn a lot with projects like this!

Thanks again.

 

[deucer]

Thanks for stopping back to the post to comment. I also picked up an exchanger box and heater out of an A3. I'm waiting on a few constant pressure hose clamps, and then I'll be able to finish up. I didn't cut down the size of the heater box like some other SS members did. Instead, I relocated the exchanger box about four inches towards the drive side. That seemed to give it enough room. I see that when I got my truck, the heater hoses were not hooked up correctly. The heater return line is hooked up by the thermostat rather than down by the water pump housing - like it is supposed to be. You certainly learn a lot with projects like this!

Thanks again.

I also added the inline cutoff valves, not only to turn off during summer but to switch off in case of a leak so it does not drain the system.

 

[bonedoc]

You guys have any more pics? Pics of how it looks with exchanger moved over, position of heater core, where you drilled through firewall? Brackets that hold it under dash. I purchased a nos heater kit for my M35A2 and want to install the heater system in the cab rather than out in the engine compartment. Thanks, any info would be a great help.

 

[tcruwithme]

You guys have any more pics? Pics of how it looks with exchanger moved over, position of heater core, where you drilled through firewall? Brackets that hold it under dash. I purchased a nos heater kit for my M35A2 and want to install the heater system in the cab rather than out in the engine compartment. Thanks, any info would be a great help.

I'll be working on my truck again on Thursday the 4th (waiting on parts). I'll take a bunch of pictures then and post them to this thread with an explanation of what I did.

 

[Wildchild467]

I used a standard M35A2 heater under the dash of my M35A2. I shortened the whole heater box because it was way too long. I then used a M35A3 / M809 Series diverter box. I also used a cable operated shut off valve I purchased at Napa to plumb inline on the heater hose. It works great. I will try to get a picture tonight and post it.

 

[bonedoc]

Thanks guys, that would all be great.

 

[Wildchild467]

 

[bonedoc]

Thank you very much. That helps tremendously!!

 

[Wildchild467]

The inline valve I used was from Napa. i don't recall the part number but it shouldnt be too hard to find. It seems like it was from an IH Scout or something.... not sure.

 

[tcruwithme]

Relocate Deuce heater into the cab

Ok, so I am just about done with my heater install. I have a 1985 M35A2C that I put a hydro power steering system into it from an M818. On this steering system, the gearbox is on the steering column. Therefore, I needed to relocate the cab heater. My options were to relocate it to the other side of the engine compartment, or to the inside under the dash on the passenger side. Inside the cab is where it went, and I got a diverter box from a 5-ton truck and a heater core from an M35A3. Here are a few pics and comments:

The first thing I did was remove the old system. Since the new system will pull air from inside the cab, I removed the old air vent in the firewall on the driver's side that routed fresh air into the cab. I bolted 1/8" steel plate on both sides of the firewall, because I have zero welding skills. On one side, I used some RTV silicone to give it a good seal. I used 8-18 stainless steel bolts, as there won't be any stress on these joints. Here is what that looks like from inside the cab and from the engine side:



The next thing I did was measure where the heater box needed to go. I didn't want to cut it down, as that would test the limits of my zero fabrication skills. So I marked off the farthest it could go to the right side (passenger side) and still allow for the operation of the fresh air mechanical vent. So, I needed to shorten the connector piece from the heater core and the air diverter box. I made a piece from 4" inside diameter (ID) exhaust pipe that would fit over the input end of the diverter box and the output end of the heater core. The piece is 1 9/16" wide, and has four holes drilled in it on each side. On one side (the diverter side), those holes are 1/4" from the edge. On the other side, those holes are 1/2" from the edge. I then ran cutting screws through those holes to get everything connected. I took this approach because I have zero welding skills. Here is a before and after shot of the 4" ID exhaust connector:



To get the coolant hoses through the firewall, I used a couple "military grade" rubber grommets I got from Grainger. They were 1" ID and needed a hole through the firewall of 1 3/8". The coolant hose I used was 5/8" ID Dayco silicone heater hose that had a 0.995" (1") outside diameter (OD). I used constant pressure sprint-type hose clamps. Here's a couple photos that show where the coolant hoses came through the firewall first from the inside then from the engine side:



Next, I connected those hoses up to the coolant system. The top port I used before the thermostat was a 1/2" pipe fitting. The bottom port by the water pump was a 3/4" pipe fitting. I decided to replace the drain cock 3/8" pipe to 5/8" hose that the military uses with ball valves. I had a couple 3/4" ball valves laying around, so I used those. The bottom port connection was easy - I used a 3/4" street elbow into a 3/4" x 1 1/2" nipple into the ball valve. Then I used a 3/4" pipe to 5/8" hose barb coming out of the ball valve into the hose. I connected the hose with the constant pressure sprint-type hose clamps. I'm not sure what those are really called ... For the top port connection, that needed a few extra pieces. I started with a 1/2" x 1 1/2" nipple and went into a 1/2" elbow. Then another 1/2" x 1 1/2" nipple into a 1/2" input x 3/4" output connector. Then a 3/4" x 1 1/2" nipple into the ball valve and a 3/4" to 5/8" hose barb coming out of the ball valve. Here's a couple pictures of what all that looks like:



Next, I flipped the motor to the other side of the heater box. Instead of the motor hanging down, I now have it sitting above. There are no clearance issues with the map box. I also removed the elbow air intake to increase foot space below the heater assembly. I still have to get some sort of screen on that air intake opening. The military didn't have a screen, but it seems like a good idea, and I'll get it done. Here's a picture of what that looks like:



Here are a couple pictures taken from looking through the open map compartment. This is where the two mounting points for the right side of the heater core attach - to the bottom support bracket under the map compartment. You can also see the bolt through the firewall for the rear left mounting point on the heater core.



Here's a couple shots of where the diverter box is positioned. I needed to use 3/4" spacers to hold the diverter box off the firewall - because I no longer had the flexible hose connecting the diverter box to the heater core. The diverter box has moved about five inches over to the driver side from its original position. It also moved down about four inches from its original position. Those distances are estimates, and you should measure your system several times before drilling any holes.



Finally, here are two shots of the system in its final resting place. So far, I don't have any leaks. I consider that a victory. Unfortunately, I ended up with several extra holes through the firewall. I'll fill those with hole plugs one of these days. I hope you like the pictures. Any feedback you have on how I could do this better would be greatly appreciated.

 

[bonedoc]

tcruwithme...B.I.G. huge thanks to you. The photos and explanation you did will be a tremendous help to me. Thanks again!! I too lack welding skills and like how you connected your heater to the diverter. System looks very clean and factory. Congrats on no leaks though with these trucks...how would you know....lol!!? I'm assuming you just cut that exhaust pipe connector down? One more question? How many brackets hold the heater core under the dash. My kit is an M35A2 heater and I think I'm going to search out and salvage a set of brackets to hold it under the dash.
Thanks to everyone else who posted pictures. Painting my cab this weekend and will hopefully have it completely reassembled in the next week or 2. Then I'll be painting the bed, then on to the heater as it will be starting to get cold here in the northeast.

 

[tcruwithme]

tcruwithme...B.I.G. huge thanks to you. The photos and explanation you did will be a tremendous help to me. Thanks again!! I too lack welding skills and like how you connected your heater to the diverter. System looks very clean and factory. Congrats on no leaks though with these trucks...how would you know....lol!!? I'm assuming you just cut that exhaust pipe connector down? One more question? How many brackets hold the heater core under the dash. My kit is an M35A2 heater and I think I'm going to search out and salvage a set of brackets to hold it under the dash.
Thanks to everyone else who posted pictures. Painting my cab this weekend and will hopefully have it completely reassembled in the next week or 2. Then I'll be painting the bed, then on to the heater as it will be starting to get cold here in the northeast.

Yes, I just cut the exhaust coupler down so that it was 1 9/16" wide. That's because the flange on the diverter is 9/16" and the flange on the heater box output is 1".

As for the leaks: there are only a couple places for the coolant to leak from in this system. If it leaked by the hose connections on the heater core unit, you would see coolant on the passenger floor. Thankfully, there was none of that. The other places are by the ball joints and connections to the engine block. Those are easy enough to see, and so far, no leaks there either. I know what you mean by leaks in the Deuce. One goes with the other!

There are four brackets that hold the heater core in place. The great thing about this heater is that you can mount it in a number of ways, and there are machined holes all over it to mount the brackets in different places. Your box used to sit on the fender, so you'll need to rotate it 180 degrees so that the coolant ports face the firewall while the air output faces the driver side of the vehicle. You can probably use two of your existing legs for the front right and rear right mounts. You will probably need to figure something else out for the rear left and front left.

 

[rustystud]

Good job "tcruwithme" ! Extremely well done !

 

[tcruwithme]

Good job "tcruwithme" ! Extremely well done !

Thank you, rustystud! I drove my truck 90 miles today, and the hoses held up to the temperature of the nearby exhaust manifold. I was slightly worried about that, but they look great.

 

[TsgtB]

I see the resistor in a pic above, on the firewall above the trans hump.
Are the mounting clips screwed into the firewall or some sort of mounting board?
(resistor mounting suggestions?)

 

[tcruwithme]

No mounting clips, no mounting board. Just screw it to a convenient place on the firewall close to the switch.

I see the resistor in a pic above, on the firewall above the trans hump.
Are the mounting clips screwed into the firewall or some sort of mounting board?
(resistor mounting suggestions?)