How to rebuild the Heater Box and Blower Motor assemblies

[kev]

This thread is for rebuilding your heater box and blower motor assembly.

 

 

Have to add my disclamer:

 

Please note: I am not a mechanic who works on cars day in and day out! I don't have an unlimited supply of specially tooling! I am an auto enthusiest/backyard mechanic like the majority of us on this site. I've done my best to document how I performed this particular rebuild using standard hand tools and the factory service manuals as my guideline. If you see something in error, please respond via PM. If you see something that may be performed in a simpler fashion, again please respond.

 

 

 

 

First and foremost: YOU NEED THE FACTORY MANUALS FOR ALL REBUILDS!

 

Parts required:

• Open cell foam of .13" and .25" thickness. See suggested part numbers that I used in thread.
• Small piece of 3/4" heater hose and some hose clamps
• As always, any replacement component for an item found bad during the rebuild.

Tooling Req'd: This rebuild was performed with just basic hand tools with exception of the following:

• 110V to 12V power convertor. Used to test electrical components out on your workbench
• Vacuum pump - hand held

Consumables:

• Green Grease: Doesn't have to be green, I just like it...but you want to use a grease suitable for bearings/axles for the internal components of rotating assemblies.
• Lithium Grease: I use lithium grease for all of the joints that aren't continually used as well as the joints that are open to the cabin of the vehicle....for the simple reason that lithium grease doesn't have much of an odor.
• Loctite
• 3M General Trim Adhesive

kev

 

 

Edit 11/5/2014: Lately I have been receiving many requests from club members asking if I would consider rebuilding their parts per the steps shown in these ‘how-to’ threads. Although I am humbled at your trust in my abilities to rebuild such critical parts of your vehicle, I respectively have to decline any such requests. With a family of four, a demanding career, and just the normal responsibilities in everyday life, I have difficulty in finding time to work on my own project vehicles much less take on additional work. However, I encourage you to review the thread in detail, try to gather the required parts and tools, and attempt to rebuild the items on your own. My goal in developing these threads was to give members the encouragement to perform these component rebuilds at home while gaining valuable experience, saving some $, and simply having fun with the hobby. I hope by sharing this information and by including my own trials and mistakes along the way, help to achieve these goals.

 

Regards,

kev

[kev]

Heater Box Rebuild:

 

I'm not going to bore you on step by step photos on taking apart the heater box...everyone knows how to use a screwdriver. However, I will show step by step installation photos showing how every piece goes back together. So tear her down to the last part. The primary purpose of this rebuild is to clean out that 25 year old box...we'lll do a couple checks on the vacuum and electrical systems and then bolt her back together.

 

During your teardown, do not disassemble the following linkage joint on the underside of your heaterbox. I guess it isn't a big deal if you do, you can set it later, but it will save you some time if you don't alter this factory setting.

 

 

Ok, tear it all down. Organize your parts and CLEAN CLEAN CLEAN. No need for mineral spirits here. Simple Green and water was all that I used to clean everything up. The parts aren't really greasy, they are just dirty. For the white plastic items, I did a quick final clean with Wesley's Bright White just to clean up the stains.

 

The cleaner the better when it comes to all mechanical and electrical components.

 

 

 

 

First thing first; test your two vacuum diaphragms.

 

The first is a double acting diaphragm for head/foot/combo that is the most common for failure. That bellows boot is the air seal! Believe it or not, but it is! The bellows boot dries out and rips with time.

 

 

 

Didn't pass this test...here is why:

 

 

This component needs replaced. I pulled out both of my spare heater boxes and found the same problem in this particular vacuum diaphragm. I tried contact cement to glue back the boot...no luck. Also tried HH66..no luck. Even on further inspection, you could see that in the ribs of the boot that there are cracks in the rubber. No sense in trying to repair this unless you can rig up a little spring return or something.....

 

You can go with a good used part (BTW they are NLA from Mitsubishi). Or do a modification suggested by another member here (what I chose). We will revisit this later on. Lets move on in the troubleshooting/assembly

 

Other vacuum diaphragm. This one is single acting with a spring return. This controls the defroster.

 

 

 

This one checks out good and is a pretty reliable diaphram...so it will be retained. Note: upon disassembly the white plastic 'nut' you see on the diaphragm had spun off and the inner plastic guide that is under it slid down. I threaded it back in for this test...but will resolve the 'unthreading' issue later on.

[kev]

Foam replacement:

 

As everyone knows the foam on the divider panels within the control box (and blower motor box) is so old and dryrotted that it crumbles at the touch. Everyone tries their best not too touch it and hope it lasts more and more....screw that. Plus my car was a smoker's car at one point in time (almost 20 years ago)...you can still smell the cig. smoke in this old foam. Enough said, lets get rid of that old crap.

 

You can see that most of the foam came off already in the cleaning process.

 

 

 

Take one piece at a time and scrap away the old foam.

 

 

This is the air diverter that diverts the air into the heater core. It had ~.25" open cell foam on both sides. So lets replace that foam.

 

Here is what I used. I bought a large sheet of it to use on multiple projects..you may want a smaller sheet.

 

From www.mcmaster.com:

 

 

 

Using the diverter as a template, trace out the shape on the adhesive backing paper, cut it out, and stick it on the diverter:

 

 

 

Looks good as new!

 

 

Next: this is the diverter for the face/foot. This is the one that is in the upper middle and is easily seen with the box still in the car.

 

This one has foam on the one side and on the other has foam with a rubber sheet.

 

Remove the foam from the side with foam only:

 

 

Flip it over. Now peel off the rubber sheet and rub away ALL of the foam under it.

 

 

 

 

Now using the same type of foam but with 1/8" thickness:

 

 

 

 

Cut out two pieces using the diverter as a template. Note: This time the foam doesn't wrap around like it did on the last deflector.

 

 

Stick it on on both sides:

 

 

Now glue back on the rubber sheet. Make sure you put it on the correct side. If you forgot which side that is, just match up the small notches on the corner.

 

I used 3M general trim adhesive as the glue. Follow the adhesive application instructions for the product you are using.

https://www.hotrodders.com/media/dsc06643-jpg.110226/full

 

 

 

 

 

Next: Defroster diverter.

 

 

[kev]

Remove the old foam. Refoam using the 1/8" thick foam.

 

 

 

 

 

Last diverter: This one has the rubber sheet with foam under on one side and nothing on the other. Repeat steps above for it.

 

 

There you go...all four diverters:

 

 

 

Using white lithium grease, apply a small bit on every hole in the plastic box where the diverters stick thru:

 

 

I don't show it here, but use a piece of emery cloth to clean up the rods on the diverters.

 

 

Other half of the box. Note that I installed that small steel bracket...if you removed yours.

 

 

Install the two diverters in the positions as shown (in bottom half of the heater box):

 

 

I lost a photo along the way...but install the top half of the heater box and snap together with the spring clips.

 

Next move on to the front two piece section of the heater box:

 

Grease up the holes.

 

 

Install both diverters as shown:

 

 

Put on other half:

 

 

Snap both parts of the box together with the spring clips:

 

 

Here is what you should have together. Take the time now to make sure that the diverters open and close the way they should...in their respective guides.

 

 

If you are comfortable with how the diverters work. Screw the front of the box onto the main box:

 

Looks like a heater box again.

 

[kev]

Next to the linkages and diaphragms.

 

First: defroster vacuum diaphragm.

 

If yours isn't this far disassembled, make it look like this. Apply lithium grease to the guide and shaft

 

Insert guide

 

 

Apply red loctite to the threads to prevent this plastic nut from spinning off again. Install nut and snug tighten it.

 

 

Bolt back on the bracket. I use loctite on every screw that threads into metal. Lube up the pin on the bracket while you are here and install the plastic bushing.

 

 

Bolt onto heater box as shown with linkage bracket on diverter panel.

 

 

Test that it opens and closes the defroster diverter smoothly:

 

[kev]

Now the harder linkage; the face/foot control

 

Here are your parts:

 

 

Follow the photos for assembly:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Bolt on your double acting diaphragm (assuming yours still works or you found a good one). Note: I'll come back to this with a modification using a different diaphragm...for those of us who can't find a working factor double acting diaphragm.

 

[kev]

Next to the servo operated mechanism.

 

Take the black plate and bolt on the potentiometer in the position as shown.

 

 

Grease up as shown:

 

 

Install linkage arm

 

 

Mount motor in position as shown:

 

 

Hook up the rest of the linkage:

 

 

Mount the entire bracket to the heater box:

 

 

Flip over the heater box and connect your under box linkage assembly as shown.

 

 

 

 

Install protector plate:

 

 

Now you a s 110V to 12V transformer to check the function of your servo motor.

 

NOTE: PUT LEADS ON THOSE WIRES! I SHOULD HAVE DONE THAT. WAY TO EASY TO BLOW THE MOTOR OUT.

 

 

Watch the diverters open and close. The extremes should be as shown below. You can adjust extremes using the linkage adjustment that I said earlier not to separate on disassembly.

 

Note: it is a stepping motor...so when you apply voltage you will hear 'click..click..click...' that is normal.

 

 

 

Ok the linkage systems are done.

[kev]

Now to the heater core.

 

Leak test the core first. I use an old bike tube to apply a couple psi of head to the system. If you want more pressure, wrap the bike tube in duct tape (I do that later in the final test) My experience with heat exchanges is that if there is a crack, it'll leak air at as low as 1 psi differential.

 

Dunk it in water or snoop out the entire core. Note: my one fitting was leaking in this photo...I corrected this leak prior to confirming that there were no leaks in the core

 

 

I used some of that 1/8" foam earlier to wrap the top and bottom of the heater core where the old foam was all mashed down. Also, if you replace your heater core, you will need to re-foam it as well.

 

Install it in the heater box.

 

 

 

Oh, I forgot there is one more linkage bar assembly. This one has to be installed after the core is put in:

 

 

Using a piece of 3/4" heater hose and two nice new hose clamps, replace that old forgot-on heater hose and obsolete clamp.

 

 

 

Connect your final linkage bar:

 

 

 

Install your pipe bracket

 

 

Plug in your t-stat...for 87 and older boxes (doesn't exist on the heater box for 88/89 cars). This t-stat is for the A/C system...which I am not using...hence why I didn't perform a check on it. If you use your A/C, check the t-stat per the FSM.

 

 

Route your wires as shown:

 

 

Install your bracket

 

 

 

One more leak test...the new rubber hose section. I don't want to find out later on that this leaks.

 

Note, I duct taped the tube to get more psi.

 

 

[kev]

Last check. We didn't test the potentiometer on the servo system during installation. So lets do that.

 

Disconnect this linkage for the test:

 

Connect your voltmeter and test the resistance at its limits.

 

 

 

Reconnect the linkage.

 

Last thing to do is to recheck the vacuum diaphragms and install the vacuum hoses and bottom deflector. But lets stop here to do the diaphragm modification that I mentioned a few times earlier. I'll start a new post for this....

[kev]

HEAD/FOOT DIAPHRAM MODIFICATION

 

 

This modification is per the instruction of ucw458. Hats off of him for thinking of a way to reuse another starquest part to solve a common issue with our cars!

 

For the face/foot actuation. The double spring setup in the linkage system defaults the divertor positions to the middle. So basically if you loose vacuum, your system defaults to the face/foot combination position. If your bellows boot is ripped, the face/foot mechanism will work fine for 'foot' only but it will never close the divertors to give you 'face'. It will simply stay at head/foot combination.

 

This modification will eliminate the face/foot combination feature in the car! You will have the choise of face or foot. It will now default to face with no vacuum!

 

The modification is to simply remove the double acting diaphram and replace it with a spare single acting/spring return diaphram as used on the defroster system. Naturally you will need another defroster vacuum diaphram for this test.

 

See photos on the modifications required to mount this diaphram:

 

Undo both springs and remove the one shown by the pick:

 

 

 

 

Mount the new single acting diaphragm using the bracket for the double acting one. It is that simple!

 

 

Note the difference in default position. This is a good quick modification. You loose the face/foot combo...a feature that I don't even use on my newer vehicles...not a big deal.

 

Do a vacuum check on the new system. It should open/close smoothly:

 

 

Might as well check the other diaphragm again..we're here

 

 

 

 

You will need to make one slight modification to the vertical brackets that get installed once you bolt the box in the car. You need to notch the bracket to clear the vacuum line. Wait until you bolt everything in the car to do this. mock up the bracket and mark it for a notch. Cut your notch and use some foam to rid any sharp edges that may cut the vacuum line.

 

[kev]

Back to the heater box assembly. Almost done. Just need to bolt on the plastic deflector and run the vacuum lines. Naturally I went with the diaphram modification on my heater box.

 

 

Vacuum lines...only two used with the diaphragm modification. Cap the other one:

 

 

Use new vacuum lines of course.

[kev]

Heater box rebuild is complete!

 

Lets move on to the blower motor box

 

BLOWER MOTOR REBUILD

 

 

Ugh...look how disgusting that is:

 

 

 

 

 

Again, not going to bore you with the teardown...just the assembly. So tear it all down...

 

Here is why you need to rebuild the blower motor! Take a look at the crud in the motor itself! Did you know that the blower motor pulls more current that almost any other device on the car when it is running?

 

NOTE: This car has been parked since 2000 in my garage...That was 12 years ago on what is now a 25 year old car. Imagine what yours looks like today!

 

 

 

CLEAN CLEAN CLEAN...and organize. Same as before...Simple Green and water

 

[kev]

Lets start with the foam replacement on the diverter.

 

From inspection of the old part: There is 1/4" foam on one side. On the other side is a sandwich containing one 1/8" foam, a rubber sheet, and an 1/8" foam overtop. So that is how we will rebuild it.

 

Clean off the diverter and clean all the foam off of that rubber sheet...we'll reuse it.

 

Spray your 3M adhesive on one side of the rubber sheet and one side of one of the 1/8" foam sheets.

 

 

Lay the rubber over the 1/8" foam

 

 

Stick the other 1/8" foam sheet over the rubber

 

 

 

Stick the 'sandwich' to the panel...note orientation

 

 

 

Stick 1/4" sheet on the other side.

 

 

 

[kev]

Test your diaphragm....looks similar huh? Same process as before

 

Lube and loctite

 

 

Bolt on

 

 

 

 

Using 600 grit sandpaper, clean up the contacts on the motor. Note how chewed up they are from all that dirt in the motor! Get them pretty smooth but don't remove too much material.

 

 

Snap in metal guide on the plastic box

 

 

Lube diverter holes...like we did on the heater box

 

 

 

 

[kev]

Linkage assembly. This one is real easy

 

 

 

 

 

 

There you go:

 

 

Test it. looking for a nice smooth operation.

 

 

Here is what we got so far...doesn't that foam look good? No more disintegrating smoke infested brown crap.

 

[kev]

Motor Assembly:

 

Place a dab of good grease in the bearings on both sides of the motor. I like using a good hi-temp grease here but don't go overboard. You don't want it leaking into the motor. The motor shaft has dust covers to keep this grease where you want it.

 

 

 

Grease the shafts:

 

 

 

 

 

Vent:

 

 

 

 

Motor is together. Test it's operation...>VERY IMPORTANT!! You want to know if you did it right now...and not when it is together.

 

Note that I wised up and put leads on my wires! lol

 

[kev]

now to finish assembly.

 

Putting on the fan and bolting it all up. Follow along in pictures, no need for words:

 

 

 

 

 

 

 

 

[kev]

new foam surround:

 

 

Look how nice that looks now

 

 

Install your wiring:

 

 

DONE!

[kev]

Photos of the final product.

 

Sorry guys, I'm deleting the A/C on this car so I didn't rebuild the evaporator...but it isn't hard to do.

 

 

 

[kev]

Link to a thread discussing removal/installation of the heater box and blower motor assemblies:

 

http://www.starquestclub.com/forum/index.php?showtopic=138420

[kev]

All photo links repaired in this thread, let me know if you see a missed link or incorrect picture.