Industrial Cab Heater Alternative

The heater in my 1978 F250 was crumbling, broken, and basically not restorable. I assume there are replacement units out there, but I opted for an easier and effective solution. In addition to high performance fans, Maradyne sells some neat industrial universal heating units for tractors and other utilitarian rigs not normally equipped with heaters. Think of a guy who bought a used forklift for a warehouse in Calgary or the guy restoring some old WWII infantry vehicle... what's he going to do to get some warmth?

Flexalite and Summit sell universal heaters under the "Mojave" trade name. The unit I picked up from Maradyne is part number 512H. It's a 12 Volt, 15,000 BTU heater that measures 7" High x 8" Long x 7" Deep. I also picked up part number 64006 which is 150" of 5/8" heater hose and part number 5670004, a switch kit with a 3 foot harness. Realistically, this type of heater blends well within the interior of any old Ford F-series but may not be the right model for a Ford musclecar. If you are looking for a more socially acceptable unit, the aforementioned "Mojave" type might fit your needs. Either way, the installation considerations are similar. Here's what I did to bring the heat back into my 4x4.


Here's the old heater from the inside. Most of the housing and ducting was loose, broken, or missing.


The heater control and cables were binding, worn, and out of adjustment.


I started removing the old system by loosening the fan from the motor compartment.


Disconnected the old heater hoses.


Just a few bolts later and the whole unit slipped out from the under the dash.


Here is most of the original heater core and fan housing materials.


I removed the heater control from the dash.


First, I needed to remedy the big hole in the firewall left by the removal of the original fan.


Here I am cutting out a template to create a block-off plate.


I traced the template onto some 1/8" thick ABS plastic...


... and got out my new Roto-Zip thanks to some tips from the FM forums. A great tool for complex 2-D shapes.


I carefully cut out my shape.


Here's the rough cut block-off plate.


I smoothed the edges of the block-off plate on a bench grinder...


... and drilled some holes for mounting.


The finished block-off plate.


I used some extra DynaMat material as a makeshift gasket for the block-off plateand firewall.


Here it is, ready to be mounted.


Hole blocked.


Now I needed to mount the 3 speed control switch that I got with the heater. I started by creating some "delete" plates to cover the radio and heater control accomodations in the instrument panel bezel. I had removed the crappy stereo after I bought the truck.


Some 3M double stick take held the delete plates in place.


The two accomodations filled.


I drilled a hole in the top plate to insert the 3 speed switch. The back...


... and the front.


The switch comes with a cute bezel indicating off, low, medium, and high air flow.


Before remounting the instrument panel bezel, I connected the wiring harness to the back of the switch per the included Maradyne instructions.


The instrument panel bezel re-installed with the new heater switch. Very rudimentary, but cool in a way.


I took out my new integrated heater core/fan unit and got an idea where it would mount. I planned to angle it toward the center of the cab.


I cut some angle iron to mount to the interior side of the firewall...


...and drilled a couple mounting holes


The angle iron mounted under the dash and on the firewall.


I measured the depth and angle to create the aluminum "cross brackets".


The cross brackets test mounted.


The cross brackets drilled for mouting and to accomodate the 1/4-20 inserts on top of the heater.


Final mounting of the brackets.


The heater mounted with hoses dummied up.


A close up.


I added these grommets to the existing heater core holes in the firewall so not to score the heater hoses I'd be running through them.


With the aid of some WD40, I threaed the hoses through the grommets.


The new heater hoses in place in the motor compartment.


Hose clamps and a manual heater core control valve I would be placing in the "feed" line, inside the cab.


The control valve can be placed in the "feed" line or the "return" line. This is equivalent to the vacuum-actuated control valve a driver normally opens and closes from the heater/ac control.


A close up of the control valve installed. Yes, I'd simply be opening this during the cold season and closing it during the warm season. Either that, or putting the passenger to work.


I connected the harness from the switch to the fan on the back of the heater.


Then I connected this white wire from the switch harness to 12V key on.


The unit worked like a champ.

Pretty cool... I just hope you don't need a defroster.

Makes me think of the old 30s cars or something that had just a heater box in them. Should put out some heat for ya.

Yes, it's not the perfect solution for every project car or truck. You need to evaluate your application and how you plan to use your vehicle. My F250 falls somewhere between a workhorse and a tank, so this was right for me. You can probably get a more aesthetic install and route some ducting with other universal heaters.

pretty cool.. I like the install. gives me some ideas. Thanks for sharing.

Seems to me, you could mount it flat and it would be virtually unseen. For the cab of your size, should do just fine whatever direction you turn or mount it.

What did you do about the fresh air intake? All that air coming in from the cowl went through the heater I thought. I could be wrong, but had to ask.

Fresh air is available a knob away... Just reach down to the drivers or passengers knee and pull the vent knob for a blast of nice fresh air.


Nice writeup Jon Just don't plan on moving anywhere cold or driving in the winter without the heater on full blast to defog the windows

Man, if my 78 Ford had been equipped with a cup holder and I removed it, you guys would probably tell me that I better stop drinking coffee. I thought a defroster was just an amenity.

"I thought a defroster was just an amenity."

Depends on where you live. Down here in Houston, if you don't have defrost in the winter, you are out of luck.