DIY -- Heater unit rebuild

My pay back to the forum; here's my approach to rebuilding the heater box from my E9. Not sure how this compares to e3, but let me know and I can possibly merge.

I'll likely chop it in roughly three pieces; removal, disassembly, repair and rebuild. I haven't installed it yet myself, so i can't do any pics of that :) .
I will add sections in the coming days, depending on how boring my meetings in the office will be....

Cost & time estimation: About 450 euro and 30 hours.

- Re-cored heat exchanger: 231 euro
- Re-zinced parts (done with other parts, so I just take a part of it: ) 30 euro's
- 1 square meter of closed cell EPDM foam 5 mm thick with glue backing: 60 euro's
- blacking fluids to recoat the black steel spring wires of the front air vents: 25 euro for a set, but used only 25% of it: 6 euro.
- a few rivets, rattle can black paint, solvent; glue for textile part inside the air duct: say 10 euro's in total.

time consumption: 30 hours; this includes disassembly, making it all fresh again, drop & pick up of the parts of for fresh zinc and recore, an re-assembly. Oh, and a bunch of photo's in between to insure myself for premature Alzheimer...

This will get you:
1. peace of mind that your core doesn't leak. Especially helpful if you don't want to disassemble half of your dash after finishing that 10 years restoration.
2. A nice and shiny center stack, with air vents that give max air volume output (sometimes blocked by sagging textile inside the air ducts)
3. smooth running fan with no noise from 45 year of gunk /leaves inside etc

Disassembly:
Getting the heater box out from the dash is difficult. It's quite some work, as it requires you to remove some parts surrounding it to give access to the screws holding it place.
If i remember well, you need to get the glovebox out, and the panel under the steering column. Besides that, you need to remove the center console sides. I don't think you can leave any one of those installed. also you need to disconnect the water hoses from inside the engine compartment.

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Unscrew bolts from the side of the front panel, they should have 2 left, 2 on right side.
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The front panel is now hanging by the control wires and an electrical connector. You can see also the rectangular air duct now comes out. Mine had only 3 screws...

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Next step is detaching the unit itself from the firewall. The Unit has on either side a large yellow zinced bracket with 4 nuts. (see green lines in image below) Detach those nuts.
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You now have it loose.

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eriknetherlands

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Disassembly step.
I am one of those guys that simply tear down stuff until the last tiny bits; really enjoy that process, trying to crawl into the mind of the person who designed it: Why did they do it like this? Where is this thing for? It is perhaps what I like the most.

Before starting the disassembly, i felt it was important to document how the rigid cables (rod? wires?) are connected between the controls and the heater unit. The setting of these cables will affect the movement of the internal flaps. If the rigid cables are incorrectly attached later on, your flaps won't be fully closed although the slide control shows you so.

For this I measured how much mm's the rigid cables stick out from their clamping element + I marked them with a red marker. Mind you; this is how it was installed in my car; the controls functioned perfectly, and I think it has never been touched before. The actual setting could possibly, but not likely, be different in your car.
Here they are in case you have already disassembled them without making measurements; you can use mine a basic setting.

There are 4 rigid cables. Each of them connects to one or two flaps. I have identified them as 1/2/3/4.

Number 1 is the top middle slide control ( Kalt-Warm) it attaches to the flap in the middle of the box.​
Number 2 is the bottom left slide control ( Zu-Luft-Lufter) and controls the amount of air flow. It attaches to the half flap in the top of the box.​
Number 3 is the bottom middle slide control (= 'Unten-Oben' : Bottom-Top ). It attaches to the bottom rear of the unit where it direct airflow to your feet or to the window defrosters in your upper dash.​
Number 4 is the bottom right slide control, in my car "Zu-Luft". It attaches to the top flap on the unit.​

Number 1; Cold-Warm; stick out on first lever is 7 mm. In the third pic you see it also links via the axle of the flap to a rigid pin which connects to another flap at the bottom of the box: I later defined them as 1A (top lever& flap) and 1B (bottom lever & flap). This way you also know which flaps belong behind which lever.
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1A and 1B identified in the pic below, already partially disassembled and unclipped from the axle of the flaps 1A and 1B:
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Number 2 operates the half flap at the top of the box, close tot where the electric cable enters the box for the fan.

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stick out is 15 mm :
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Number 3 operates the flaps directing the air to your feet or the upper dash defrost vents; stick out of the wire at the clamp is 7 mm.
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In this picture you see that the rigid cable 3 also connect trhough the lever to a wire going through the box to also operate the foot/dash selector flap on the other side.
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Number 4; the top vent, sticks out 8 mm:
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same as above, but now marked with red marker.
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Now that we have know how it should all go back together, we can continue the disassembly.
Removal of the controls: Push off the knobs from behind with a screwdriver. People that have an original car will see that each metal tabs has a small black plastic sleeve.


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2 screws detach the air vents with light panel:

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remove the little snap clips that hold the light guide to the air vents by bending them open; push a small screwdriver inside and flip one side of the clip open.

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Now the light bar is loose: My car has a Swiss origin, so i have German language controls. The lights insert from behind, and allows the letters to be read in the night.

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this now allows us to clean everything. The light guide is painted plastic, clean with a toothbrush with soap and water. Be careful with solvents as they may remove the black paint.

Continue to disassemble the air vents:
Unclip side clips; first step is a light tap or strong thumb push to unclip them.

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second step; now unclipped, then still need to move outwards; this is a bit of a struggle. Best way is to push from behind to slide the clip off the axle.
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final result:

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Now the airvent slides out of the metal frame:
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Further disassembly of the air vents. These are usually dirty, and the thin wire springs are sometimes rusted/rusty.
Remove springs with a small screwdriver:

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The air guide has a textile inside layer original from factory. Often it is hanging loose. Some people remove it. I choose to reinstall it. I think it is intended to reduces the chop-chop sound of the air flow, but I'm sure it does more in restricting the airflow then in reducing the sound.

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eriknetherlands

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Having identified what goes where, you can tear it all apart.
start by removing the pivots and hinges. Do make some pic by your own so that you know which levers go where.
I labelled all my pivots/ hinges with 1A/1B/2/3/4 and put them in separate bags with their respective nuts and rings, prior to re-zincing them.

It works best by placing the unit on a table on it's side, with the cables on the bottom. Supporting the box with a wood block will ensure that it is nicely upright and somewhat stable.
- Undo the C-clamps on the side. Remove the grille and disconnect the motor.
- The electric cable is glued water tight through an opening ; I kept it just like that.
- Then proceed to lift the top half of the housing, taking note of the 2 rings on the axles of flap 1A and 1B.

you'll pull out 5 flaps, i labeled them 1A/1B/2/3/4;
(note size of foam piece 1B should be 5x130x300mm (not 5x100x300)
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2:
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3:
are the 2 foot flaps; no foam there: Use a screwdriver to push the axle out:


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flap 4 has a neoprene (diving suit material) foam:
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foam folds around the axle:
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drill out rivets; remove & label the parts coming off: rings and cilinders ( 'dopje' means cap, it's the small cilinder on the axle of 1B)
Rivets are 4mm diameter.
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I label and photograph all sets, this helps to identify the pars once i get them back in a bucket with a 1000 other nuts and bolts from the zincing company.

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eriknetherlands

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The fan with motor is easy to get out: remove the 3 screws to get the protection thing off. This exposes a plastic ring that locates the fan and motor. Disconnect the electrics and lift out. It easy if you do this actually as the first step during your disassembly...
20201013_212751.jpg


Put the white fan in a vice, and remove with a screwdriver the black halves around the motor.
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the black halves have a snap clip on the sides:
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Remove the round small black cap; it has small snaps on either side.

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This allows you to lift out the red part with the brushes. (mind you the motor is still available from Bosch for ~85 euro (info Sept 2021)) .
My brushes were fine, so I only cleaned everything up nicely and lubricated with a drop of thin oil.

20200604_084810.jpg


the motor can be pushed out of the white plastic fan. This allows for easy cleaning of the fan: just soak it in your favorite solvent. The fan also has balancing weights attached to it. If removing them (mine had some rust), then do note their position, helped by the angle values on the white part. Also note that they can be at the top or bottom of a blade.
On my fan were thin and thick clips that act as mass balance. Don't loose 'em or you will get a unbalanced thus noisy fan.


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eriknetherlands

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IF your heater core / exchanger looks like this, then it's best to get it recored. Google radiotor shop in your neighboorhood. they desolder it, glass bead blast all the seperate components, made a new custom core (no standard cores available appearently), solder it back together and paint with 2K epoxy.
It cost me 231 euro's to have it retrofitted with a new copper core (upgrade from the steel one that it is originally)
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i then gave it a nice black layer for moisture protection:
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continued with blacking the steel wire springs of the air vents and the mass balances of the fan:
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Zinced a bucket of parts:

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eriknetherlands

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With all cleaned, re-zinced and repaired, it is time for assembly.
Others who have done the same exercise have also encountered broken plastic housing. This was remedied by those members by riveting an aluminium plate over the crack, combined with epoxy glue. In my case the housing was OK, so no need for such fixes.
(if anyone has pics of such repairs, just send them in (or link) and I'll add them here.)

Assembly sequence is quite straightforward;
1. flaps into half section of housing
2. attach the link mechanisms
3. assembly of heater vents and control unit
4. install of fan/blower/motor.

Rezinced flaps get new foam. EPDM closed cell foam 5mm thick with adhesive backing was chosen. Using my laptop to verify the dimensions to pics with measurements upon removal. EPDM holds up very well in warm and humid conditions; (PU foams like some of the original flaps) disintegrate over a lifetime of 10 years.

20201011_220535.jpg


The foam is held in place originally with rivets+glue. Rivets are 4mm diameter; I've used stainless steel rivets combined with fresh zinced rings.

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New foam around heater core to prevent air leaking around the core. Less air leak, means more effective airflow through the exchanger. with 5 mm foam, it is snug fit into the housing.
20201011_233316_resized.jpg


Foam part on the seal to the firewall was originally 10 mm. I've just stuck 2 sheets of 5mm on top of each other and then punched 2 holes in it using a half inch water pipe clamping ring.

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Flaps that direct air to feet or window screen; plastic parts cleaned and reassembly with fresh zinced parts.
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re-glue of textile inside the heater duct (i can understand if people simply leave this out)
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Assembly fan with motor:
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assembly then continues.
- Install the 2 small plastic foot flaps.
- Then insert the flaps one at a time, locking them in place by attaching the levers before sliding the next one in.
- When all 4 are in, then continue with the heater core.

Don't forget the 2 little cilinders that ensure correct positioning of the flaps 1A and 1B : (see green encircled below):

20201014_194650.jpg


Next step is the one that has many owners challenged: Each flap is on an axle that needs to go through it's corresponding hole in the other housing half. How to get all 4 aligned at the same time? Answer is you don't; you do them one by one. You start at the top of the box, and work your way down.

I've used that method and it took me one go and just 3 minutes. This way the gap between the housing halves gets smaller every time on axles slides into place, keeping the already placed axles in their respective slots. I've put a 4cm thick wood block under it to allow for easy manipulation; see pics above and below.

Start by putting the other half housing roughly on top.

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step 1. Insert this axle first, it is the axle at the top of the box.

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step 2. (that's why two fingers...) Next axle is this one.
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3rd step, (3 fingers...)
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step 4. last axle is the one near the bottom.
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Close the box up with the "C" clips joining the two housing halves.

Final step is the control unit; all that is left is this Lego work; quite straightforward if you've disassembled it yourself.

20201015_214544.jpg


After this i also made a new seal for the housing to the firewall. It is available from W&N as one piece stamping (link to be inserted later), but as I had the foam material already i made it myself, stacking two layers to give a thickness of 10 mm.

Last thing: check for left over screws....

All Done!

Let me know if you are missing some info or pics. My fully assembled unit is still in an box waiting for installation in a year or 2, so i can make some additional pics if needed.
 

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halboyles

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Wonderfully photographed and detailed writeup! Thank you.
 

Blinkling

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This is so nice, having all of these quality photos in one place. The re-zinc'd parts are gorgeous!

I'm interested in the textile piece inside the heater duct. Did you reattach it? Do you suppose it's there in order to reduce the noise coming from the vents?

Thanks for all this!
 

eriknetherlands

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Thanks for all the kind words. Hope it is helpful to someone, just as I find many helpfull things myself here.

I did glue the textile piece back. I thought it would disintegrate during dismantling, but it was quite intact. I gave it a good clean up with washing-up also.

What it does?
Well, first of all it reduces the airflow quite effectively, even if glued tightly to the inside, although I do think the original intention must have been to quiet the system.

Fyi, no single air duct in modern cars have this, so it must have been an "experiment" I think.
Cool, our cars now fall in the 'experimental' category...
 
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bavbob

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Awesome. I had to use a smattering of images from a million sites to do this, now all in one place for my next life.
 
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bluecoupe30!

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I just recently needed a new Bowden cable and PRDesignsf is all over this. They have been rebuilding 2002 heaters for years and recently branched out into E9s. I needed the cable that runs inside the 'box that switches from demister to heat into cabin. Brendan made a replacement up in no time, with the correct 3 ring loop end. Exact, correct replacement part. Where else can you get this?
 

eriknetherlands

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@eriknetherlands I'm missing this Bowden wire:
Where does it go connected in the heater box?
Tks.

I think that is cable 1, the hot-cold setting, connecting to 1a&1b. In post 2 above, the first, second and third pic show it's connections on the side of the box.

If you have all other cables, you should have just these 2 left 'empty'.

Erik.
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