Project: Heater Box

For the winter of 2022, I needed a project to keep me occupied while Peer Pressure is in the garage. I figured I’d find a used heater box and overhaul it, and maybe in the summertime swap it in with a new heater valve, which is old and bound up. After months of looking and three different parts Scouts, I found a very clean box for $50 and snapped it up.

Removing it is pretty simple: there are two screws to remove on the inner fender and two nuts on the firewall; cut or loosen the hoses and disconnect two linkages. Then it comes out with a little wiggling: this loosens some 3/8″ foam that seals up the air collection and distribution ports. The one I got was in fantastic shape, and the foam looked almost brand new on both sides.

I sprayed the whole thing with PB Blaster and used an impact gun to pull the screws out, which allowed access to the heater core and motor assembly. This heater core looks to be in excellent shape so I may just clean it and re-use it; new units are $100 and don’t have 90˚ elbows at the connections like the OEM units do. This means that the hoses go straight into the washer bottle and you have to either splice in an elbow or finagle the hoses in an arc without collapsing them.

This one only had a bit of flash rust on the inner and outer surfaces. Even so, my plan was to take it down to bare metal and refurbish the whole thing, so I started with some spray stripper and had terrible results. It was able to lift the top layers of paint off but sort of gave up after that, so I shelved it and went to the blast cabinet. Lesson learned: sandblasting > stripper. After dialing in my secondhand Eastwood cabinet with a new pane of glass and a new ceramic tip, I used gravity-fed sand to blast everything down to bare metal, including the fan element. So satisfying.

I ordered a can of Eastwood rust encapsulator with the new tips, and coated the inside and outside of the box with it, figuring some extra insurance is always a good thing.

I found a square of industrial rubber at the local ACE hardware, meant for plumbing and other repair jobs, and used that to replace the brittle black rubber stapled to the flap inside the blower housing. I just bent the staples open carefully with needle-nose pliers, punched new holes in the rubber, and bent it all back into place.

For reassembly, I used #10 1/2″ screws to hold all of the parts together. I shot them with black paint first and then assembled the bottom of the radiator well. I found a roll of sealing foam 1/8″ thick and 2″ wide, rated for 150˚ and heater applications. The width makes it perfect for fitting on either side of the core and cutting down for other areas. The trick is to pad each side of the core so it doesn’t vibrate around, on both sides and top and bottom.

I turned my focus to the electric fan motor. The motor itself is in good shape and tests fine on the bench, so I figured I’d just sand and paint it, clean up the wires, and replace the connector. Someone had cut and spliced the wires and wrapped them in miles of electrical tape years ago so I pulled that off, cleaned up the solder, and put heatshrink tubing over the joins. Then I replaced the connector with a new Delphi 56 Series 2 Pin connector and closed everything up. Using the original rubber gasket between the motor and the mount, I bolted it back up to the plate and re-installed the fan (The fan itself got a light media blasting and then a light coat of rust encapsulator). I soldered a new connector on the ground wire. New motors are available from the Light Line dealers, but there are also units available on Rock Auto for half that cost.

Next is the hose and valve unit. The inlets on my heater core are 5/8″, so I got a 5/8″ valve from RockAuto for $23 and a length of 5/8″ ID hose from my local NAPA to cut down. With all of that in place, the unit looks really good, and it’s ready to go into the truck when the weather warms up. I can’t wait to install it and enjoy a working heater control.