David Butcher's Datsun Roadster Heater

Mon Jan 01 20:36:04 PST 1996

Well, here goes. I have made some modifications to the stock 67.5 roadster heater, and I am in the process of rebuilding it due to a leak in the heater core. Here is the blow-by-blow:

Fisrt, I had to deal with the fan. This centrifugal, squirrel-cage blower is mounted up under the passenger-side footwell. Three bolts hold the fan in place, two near the top and one in the back. The large black rubber intake duct can be loosened simply by pulling it back from the fan faceplate. Up above, there is a compression ring that can be loosened with fingers to allow the rubber intake duct to be free of the heater and the air supply port at the bottom of the air distribution plenum. There is a control wire passing through the rubber duct, but the duct will rotate around it. The first bolts to loosen are the back bolt and the upper left bolt on the heater. When both bolts are loose, rotate the heater around the third (upper right) bolt so you can reach it more easily. Unplug the power wire, and remove the third bolt. The heater will drop into your (face) hands.

I have to tell you, I am not a "fan" of sleeve bearings, and that is exactly what this fan has for the blower shaft. My first "invention" is ball bearings for the fan. Begin by removing the fan motor from the housing. Remove the fan itself (the squirrel cage) from the motor shaft. I marked the two halves of the motor at this point with a marker so I could put it back together in the same way it came apart. Then "crack" the motor by removing the nuts from the long bolts that reach through the entire motor to the opposite end. The motor will split in half. Pry a little with a thin screwdriver if necessary. Now unsolder one lead from the field windings so the motor can be completely disassembled. Undo the internal nuts that hold the brush carrier in place. Move the brush carrier off to one side, and unclip the circlip from the the front of the motor shaft. The armature should be removable at this point. Be careful! The brushes will hyperextend when the armature passes by them, and they are fragile.

Now for the fun (but mission critical) part. The bearings in the fan motor are felt-reservoir lubricated bronze self-centering bearings, held in place with steel "fingers" that retain the felt lubrication washers and the bronze bearings. Your goal is to remove the "fingers", felt and the bronze bearings, and insert ball bearings in the hole where the old bearings and felt lubricators used to be.

I had some ball bearings in my junk drawer that came from a laser printer shaft assembly, and they happened to be exactly the right size for the motor shaft.

The bearings are Japanese:

NTN 607Z
That's six oh seven Z (like ZORRO)

The bearings will be a little small for the holes left by the fingers/felt/bronze bearings, so you will press them into thinwall PVC pipe, then press that unit in to the old bearing holes. Get two of those bearings, or similar quality bearings, a foot of PVC (white plastic) pipe that fits over them snugly, and get ready to take some risks.

Warning: There is no turning back after the next step.

Cut short pieces of pipe, just long enough for the bearings to fit in. Press the bearings into the pipe pieces. Tap the bearing/pipe units into the old bearing area. The PCV pipe will fit tightly, creating friction that will hold the bearings in place. The only true goal is to have the bearings centered and parallel to the shaft, which is easy if they "bottom." The armature will prevent the bearings from "falling out." Good luck - make sure you tap on the outer bearing race, not on the center race.

Note: I revised this article after taking the motor back apart to check the brushes again. While skateboard bearings would probably fit in the holes left by the older friction bearing assemblies, they have too large an internal diameter for the shaft. A truly brave inventor might consider building up the shaft with shrink-wrap tubing, for example, but I think that is beyond even my nerve. (For the curious, two concentric pieces of 1/4" heat shrink tubing worked perfectly....)

After you successfully install the bearings (and I know you will), use the shims that were on the armature (so THAT'S that those little thin washers were!) to adjust the clearance between the bearings and the armature to a minimum. The motor should just barely go back together when you are done. Technically, there should be some "end load" on the bearings for longest life, but I think they will outlast the car no matter what. During reassembly be extremely careful with the brushes. Mine looked fine, so I did not replace them. Now is the time, if your brushes need replacing. I used wooden popsicle sticks to reach in and push the brushes back then the armature was being reinstalled.

Now test the motor. Fingers first - should feel like buttah! Then the battery charger - it should spin fast and quietly. Lower amp draw, too. No spin? Take it back apart. Probably a brush issue. If all is well, smear a ring of silicone rubber all around at the seam where the motor cracked in half, and reverse your removal procedures. Voila!

The next section deals with the leaking heater core.

Now this is work. Under the hood, loosen the clamps on the hoses leading to the heater core. Loosen only one end of the very short (2") hose leading to the heater core from the heater valve - the heater end. Use a shop vac to vacuum all the water out of the heater core by sucking on the end of the hose that does NOT go to the valve.

Tip: I installed a piece of hose in a loop from the heater feed pipes exiting and re-entering the engine to "short-circuit" the heater so I could still drive the car while the repairs were being done.

Make sure there are no hoses clamped on the heater, then move inside the car.

Tip: Remove the passenger seat.

If you have not removed the fan, this would be a good time to remove it. See above. After the fan is out, there are four bolts to remove to allow removal of the heater. Two are on the firewall, and two are on the "hump" near the front of the heater unit (at the bottom). Take them all out. The heater should be "loose" at this time. The two defrost ducts would be unhooked from the top of the heater, and the rubber defrost "saddle" will probably be OK where it is. It should deform enough to allow the heater to be removed. On the upper right and left corners of the heater there are metal "ears" holding the wires in place. Bend them out of the way and loosen the cables. I removed the whole unit by pulling it out from the firewall until the copper pipes cleared the firewall, then moved it over to the drivers-side footwell. The heater wire goes inside the unit where a power resistor controls the speed of the fan. I left that wire in place. Working in the cramped confines of the drivers-side footwell, I loosened the four small phillips screws at the top and bottom of the unit (in the front) and pulled (with a lot of force!) the front "flapper" doors and their supports off the front of the unit. The heater core is packed in place with felt and foam rubber - carefully remove it and the heater core will fall out into your hands.

Well, I had a decision to make at this point - rebuild the core or buy a new one. I thought it over and decided to go for the new core. Here is what I got:

Genuine Nissan Part:




It looks good right out of the box - the felt and foam strips that were in the old heater are glued to the core, so it is ready to install. Blowing through the tubes produces almost no back pressure.

I also bought new grommets - the old ones had dissolved to a gooey mess. Taking a tip from our group, I ordered both the originals and the same part from a 240Z just in case the parts for my car were out of stock. I did not want to make a second trip. What a surprise - both were in stock!

Genuine Nissan Parts:

Roadster Grommets

SOP 00951-11000

$.93 each

Z Grommets

SOP 27243-28500

$1.74 each

There is a difference in the grommets. The Z version is a little larger in outside diameter, and the whole in the middle is about the size of a BIC pen. The center material is thin and flexible, so I believe it would stretch over the heater tubes, which are approximately 1/2 inch.

The Roadster grommets have a center hole which is the same size as my wedding ring. They are also more contoured than the Z version. They look like this from the side:

Z Grommet:
/                       \
==                     ==

Roadster Grommet:

   /                 \
  /                   \
 /                     \
 =                     =

The Z grommet is larger in diameter, but the groove is deeper, so it appears they both fit the same size hole in the firewall. I plan to use the Roadster Grommets, with the "cone" pointing into the engine compartment (unless someone writes me and tells me the cone should point the other way!).

I am also going to coat the grommet with a thin layer of silicone rubber, to keep the ozone off of it. Silicone attracts dust, so the grommets will not be shiny black. However, I have been doing this to critical heater hoses for a few years, and when the silicone is peeled off the underlying rubber always looks as good as the day the hose was installed. Since the silicone has to dry, the project will continue tomorrow.

With dry silicone, the grommets were installed. There are really two sets of grommets, the ones in the firewall and the ones on the back of the heater plenum. The grommets on the firewall were completely destroyed, and there was residue from the grommets that had to be scraped away before the new grommets were installed. I ran a dull knife through the groove in the outside edge of the grommets to break any silicone "dams" that would make the grommets harder to install. They went in from outside the car, reaching from the passenger side into the engine compartment, without a hitch.

Now the plenum is going to get repainted, which means it need to be removed from the car. The power resistor inside the plenum (used for low speed) is permanently wired, so the wires will have to be undone at the switch. Here is the color coding for my car:

Top wire: Pure blue, with a red
plastic band

Middle wire: Turquoise with a white

Bottom wire: Blue - but this wire
comes from a different loom, and it
does not have to be removed.

There is a silver sticker on the back of the plenum - Ninon Radiator Company Serial number 000252. I am painting the plenum with Hammerite Black spray paint. The finish is "pebbly" instead of flat, but Hammerite is the best rust-resistant paint I know of, and it dries fast. I will cover the little sticker with vasaline before I spray that side. I will also make sure no paint gets on the resistor, where it might cook out a smell or even catch fire.

The plenum is drying, so I will now work on the faceplate/door combination. This unit was held on with 4 screws, two top and two bottom. I have stainless replacements for them. The most disappointing part of the front doors is the foam rubber that lined the back of each door. It is completely worthless. I used a wire brush to remove what was still there, and I will use EDPM weatherstrip to replace it. I chose MD brand 3/8 wide by 17 feet long K profile, hoping the pressure on the doors would make a tight seal. (P profile would work, but the contact point is more critical. In fact, I gave up on the EDPM and used 1/2" wide by 3/8" thick open cell foam on the doors instead).

I also lubricated the door hinges with Radio Shack's precision Teflon lubricator, and torqued one of the arms so the passenger side door would close more tightly. Then is was time to paint.

Painting is tricky, with all the angles to be covered and the places that should not be painted. Take it slow. I wish I had new grommets for the plenum as well as the firewall, but the plenum grommets were in better shape, so I kept them. They will get the silicone rubber treatment, of course.

While the blower and heater plenum are out, you have an opportunity to test the resistor. I simply used the blower and a battery charger. I hooked the ground clip to the fan housing, and then plugged the bullet wire from the fan into the corresponding lead on the plenum. Now I could attach the positive lead from the battery charger to either of the power leads - the wires that used to go to the switch. Do not leave low power on too long, because the resistor will overheat if the fan is not blowing right at it. My resistor tested fine using this setup. Look for corrosion on the leads you are working with if your fan has been intermittent. I will put silicone dielectric grease on the spade lugs before I reassemble the unit, to prevent corrosion at the points of contact.

Intermission. You may have noticed I switch case several times in this document. That is because some of the text was typed from memory, and all the first person text is being typed in on a Model 100 (Radio Shack Portable) in the garage as I do the work. The laptop is attached to the Webserver as a dumb terminal, so I am logged in to the server and Yes, I am editing the HTML file with 'vi' on the Model 100, 8x40, in real time. Now back to work.

While the paint was drying, I tried to rebuild the feather-edge of the remaining grommets in the heater plenum. It looks ugly, but it will be behind the plenum where no one can see it. The silicon rubber should protect the remaining life of the grommets and provide a better seal around the pipes. Note that the pipes are NOT in there yet - the core is not installed. I will poke the core feed tubes through these rebuilt grommets when the silicone rubber is fully dry. There is no danger of the core becoming "glued" to the plenum.

While the silicone sets on the plenum grommets, I took a look at the new core. The felt pads that were soaked with antifreeze on the old core had become detached from the core, and a foam gasket strip on the top and bottom of the core had rotted, allowing air to bypass the core. I attacked the new core with the EDPM weatherstripping, plugging holes and laying a strip on either side of the foam tapes, so they will have help with airflow control. I also added a strip to each "ear" in the plenum where the core will bottom out as it is inserted, so there will be no metal-to-metal contact and perhaps a little more vibration prevention.

The barn-doors are almost dry, so weatherstripping them is next. The old foam was on the inside of the doors, but I have the option of putting the weatherstripping on the face of the plenum or on the inside of the doors where the old foam was (or both!). It looks like the best rebuild will be to place the weatherstrip on the inside of the doors, where the old foam was. However, my measurements show the thin foam I bought is too thin to bridge the gap between the door and the faceplate. I'm off to the hardware store to look for alternatives. The answer is 3/8" thick by 1/2" wide open cell foam rubber - MD brand again. It is self adhesive and very soft, so there will be little pressure on the doors when they are closed. This foam tape is actually too wide, so I cut it lengthwise before I installed it.

Tip: Perfectionists will want to budget at least 30 minutes for the foam installation ;-) This foam is thicker than the OEM foam, so it will need some time to compress before the fit is as good as the original version.

Now the reassembly begins. First, before you forget, wipe that vasaline off the tag. See how nicely that worked? Now gently ease the core into the plenum, watching all that extra weatherstripping you did to make sure it stays in place.

Tip: Now is the time to replace the rubber hose that drains the air intake system by running the water down next to the transmission. It is in plain sight. Mine was OK, so I left it. Someone in the Datsun group mentioned this hose. If you are desperate to replace it, consider flexible aluminum ducting - the kind used in many pollution control systems. Since there is no pressure on this tube, it can be very thin. Attack any cracks with silicone rubber if you choose not to replace the hose.

When installing the heater, the front doors must already be in place. Since the defrost "saddle" must also be there unless you have terrific dexterity, the finished unit will be fully assembled and very bulky.

Tip: Go to the hardware store and get a pack of re-usable stick-on clamps. These little gizmo's are plastic, and they clamp or unclamp with a finger, usually around an object the size of a pencil. The base of each clamp is sticky foam tape, so they can be installed in seconds, and then they can grab all those pesky wires that are about to interfere with your work. There is a minor loom running right above the heater, and it is now tucked (and clamped) way up out of the way on my 1600 using two of those clamps on the underside of the air plenum. Totally invisible and very organized. Oh yes, the speaker wires for the right speaker run through the same clamp ;-)

If you disconnect the control cables for the heater air intake and the passenger fresh air duct, you can completely reassemble the heater and then gently slide it in from the passenger side. The defrost "saddle" is a close fit - work carefully. I used a screwdriver on the driver side to hold the two windshield washer tubes up out of the way of the defrost saddle. Poke the screwdriver under the tubes and then up into the support for the windshield wiper motor. It should hold them out of the way. Of course, an assistant works well here also!

Bolt the heater in with the 4 bolts you took out when removing it. I smear a little teflon/white lithium grease on the bolts so they will not rust in place, and they go in easier. Hook all the wires back up, and then lubricate the air controls and get them reattached. Test everything, including the heater blower at this point.

At this point I should warn you - my heater had a "flat spot". If you have no tolerance for pain, you should not read about the hand-made brushes I created to replace the worn brushes in the motor.

With good brushes and bearings, and a freshly installed core, you are ready to hook up the hoses. I used Gates "green stripe" 5/8 hose, and there is a whole new story in this choice. It will have to be told later. The warning is: the hoses have to be 1/2 inch at one end and 5/8 at the other!



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David Butcher
davidbu at www.los-gatos.ca.us
Tel (408) 978-5495
Los Gatos, California 95030
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