VW Heater Box Lever Modification

I bought two new heater boxes to replace the ones on my '64 Bus (with '68 Beetle 1500 engine). The boxes on the Bus were the old style, 50 mm outlet ones and the replacements were the new style, 60 mm outlet ones. I had to modify the operating levers from the old boxes a little to get them to fit the new boxes. This page describes the modification, with pictures.

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Here's the old heater box, as it came off the engine. No extra charge for heater cable extension done by the previous owner.

Old heater box

Here's the new heater box, as it was shipped to me. This part is made by Dansk.
New heater box

First, unhook the torsion spring from the operating lever.

Torsion spring removed

Next, remove the E-clip on the operating lever pivot. If it's crusty, you might break it while removing it. No big deal - just get another at the hardware store. I used a pair of needle-nose pliers to remove it - sometimes it helps to use a small screwdriver and pry between the clip and the pivot pin.
Removing E-clip

Now, remove the push clip on the flap arm pin. You can just grab it with a pair of pliers and "walk" it off the pin. Note the marks on the operating lever from the push clip...it is normal for the flap arm pin to slide back and forth a bit in the slot as the linkage operates.
Push clip

Now you can remove the lever from the old heater box. Try it on your new one - you may be lucky. I wasn't.
Old lever on new box before modification

The problem was that the flap arm on the new box is wider than the flap arm on the old box. For reference, the photos have a US quarter, which is about 24 mm diameter.
Flap arm, old box Flap arm, new box

I just bent the lever with my hands to make up the difference.
Operating lever before bending Operating lever after bending

Now the problem is that the slot in the end of the operating lever won't fit over the flap arm pin anymore. I put the old lever on the new box (flap closed) and pivoted the operating lever back and forth, scraping the underside of the lever against the flap arm pin. Then I held the flap arm all the way open and did it again. This will mark where the new slot needs to go on the operating lever.
Locating new slot on operating lever

I drilled two holes, each a bit bigger than the flap arm pin, in the operating lever to form a new slot. You might prefer to drill one hole and lengthen the slot that is already in the lever. Yeah, I got the slot a little off-center...
New slot on operating lever

Put the operating lever on the new heater box and work it through its complete range of motion. If it binds or hangs up, you need to file the sides of the slot smooth, or lengthen the slot by filing or drilling another hole.
Testing operating lever with new slot

Once the slot is taken care of, you can work on the operating lever pivot pin. The old one had a groove in the end for the E-clip, and the new one was missing the groove. I put the groove in with a cut-off wheel in a Dremel tool, but you could also use a hacksaw. The groove needs to be as wide as your E-clip is thick. The depth of the groove depends on what size E-clip you have. If you're not sure, just duplicate the groove on the old heater box as closely as you can. (Yes, the photo of the old heater box pivot pin is horrible.)
Groove in old pivot pin Groove in new pivot pin

When you're done with that, you can work on the torsion spring. On my old heater box, the skin had a hole in it to anchor the torsion spring. It was missing on the new one. I just used the old spring to locate the hole on the new box and drilled a hole in the skin. Note that there is a little flat place in the skin around the pivot pin - the hole should go on this flat place.
Careful! Don't drill deep into the heater box, or you might puncture the exhaust pipe inside! Just go through the sheet metal skin of the box. If you want to make sure, put a little tape around the drill bit about 1/8" (3 mm) from the point of the bit, and only drill until the edge of the tape touches the metal.

Old torsion spring hole Locating new torsion spring hole

Once the torsion spring hole is drilled, you can start putting it back together. Put the torsion spring over the pivot pin, and put the lever on the pin. Make sure the flap arm pin goes through the new slot you made. Work the operating lever back and forth again a few times to make sure it works smoothly. Put the E-clip on the end of the pivot pin.
Replacing E-clip

Put the push clip over the flap arm pin. Put one end of the torsion spring in the hole you made and hook the other end over the operatng lever. Lubricate the pivot points, and you're done!
All done!

Last updated Sun Dec 17 03:59:59 CST 2000
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