Guide to changing the heater matrix in the cabin.

[Redfox 10]

Hi all,

I just spent some hours doing that job, so I thought it may be of some use (or not) to others.

Here's a quick guide to changing the heater element inside the cabin in a Corrado. Mine is without aircon, so note that. I may have forgotten something, so feel free to add that as a comment in this thread.

A quick guide to changing the heat exchanger:

1/ Battery poles off, first minus, then plus.

2/ steering wheel off as well as stalks.

3/ all undertrays below the dashboard off, both left and right side.

4/ instrumentation screw covers off, instrumentation frame off, instrumentation multiplug and eventual vacuum hose off.

5/ glove box off. It can catch underneath, so look at the lower edge. It's also easier and give a little more room, if you pop out the glove box light first. Let it rest in the box, and once the box is out, turn the light and lift it out.

6/ all buttons off, radio out, small buttons that control heating off. heating frame off, cigarette lighter off. Undo the 3 screws that holds the HVAC cables (two black and one blue cable, but don't take them off the control plate.

7/ Undo the bolts inside the cabin that holds the dashboard: one each end under a big plastic cap. Undo one black screw inside the dashboard in the binnacle hole, on it's right side (left hand drive car). Undo one bolt behind the lowest part of the center console, from behind. Unclip all the wires from it's holders inside the dash. Undo the reis for hte fan on the extreme right side, under the HVAC system.

In the engine bay:

8/ Take off wipers, raintray, and ignition coil, and release the stripped up wireing near firewall, and move it slightly forward. Undo very important ground wire from ignition coil holding bolt (to top of gas valve).

9/ At the fresh air intake, there is a clip at the end towards the side of the car, move that in that direction, and lift out fresh air intake tray with gasket underneath.

10/ under the top of the firewall in the raintray, there are two nuts, one each side, that holds the dash board. Undo those two nuts.

11/ undo the coolant filler tank and it's bolt cover (pop off) to gain a little more space to work on.

12/ You can now lift out the dashboard towards the passenger side.

13/ there are three nuts that holds the HVAC heating system from the engine bay side. These are situated one each side a little lower than the rain tray. They have a small nut with a big washer under it. It is VERY important to make sure that there is NO RUST on the threads, before loosening them. So clean the threads carefully and give them a dab of rust remover. If not, you risk that the other end of same bolt spins loose and it's problematic to take it off. They have a thread each end - one into the HVAC or dash, the other end sticking out into and through the firewall.. The third nut similar, sits in the middle of the soft silver heating shield on the firewall, opposite the exhaust. You can reach down and take off the nut from the generator side of the car. You don't have to remove any heat shielding.

14/ Once the HVAC heating system is exposed freely when the dash is out, in the middle og the car, is a part that looks much like a wide cow horn, that directs air to each side and up to the front screen. That is bolted on in the center with two black plastic nuts. Undo those, and lift out the "cow horn" system.

15/ At the passenger side, right under the air outlet, from below, is a big black finger nut. Unto that.

16/ At the foot of the center console, is a semi-round bracket that sticks up. it's held on the the center console floor by a few nuts. Undo those and remove that bracket.

17/ You can now press down the passenger side slightly, pull towards you in the passenger seat, and twist the whole HVAC system and lift it out through the passenger side door.

18/Looking at the HVAC, it's kind of split horizontally and vertically. Left side is the main part, right side is the fan etc. Move slightly, only little, the built in clip that holds the fan and rotate the complete fan slightly, and it's loose. Lift it out and put it aside.

19/ The vertical splitting is done now, by using a small screwdriver to free the 6 clips that holds the left and right side of the HVAC together. Put the right side aside.

20/ The left main side of the HVAC have 3 flaps, two big in metal (with holes in them) and 1 smaller in black plastic. Clean them completely for old rotten foam on both sides of each flap. If not, rotten foam will soon blow out, and you can no longer control air flow in the HVAC system. So it has to be done. Measure pieces of new fresh self gluing foam in 2mm thickness, bought from say an electronics shop or in a sewing shop, and glue them in. Move the two control buttons on the cable management plate, to move flaps, so you gain access to all flaps, all sides. Check for movement.

21/ Clean all HVAC inside and out as best you can. Window cleaner is fine on a dish washer towel or microfiber cloth. Grease all cable links on the HVAC cable control plate.

22/ Get some new thin self gluing sealing a la door sealing in a building market, and cut to suit where ever there is a rotten foam sealing, e.g. on top of the "cow horn" air system, and a few other places, like for example the topside of the right side HVAC system, (at the fan end), where it meets the big square hole in the rain tray in the engine compartment.

23/ your system is now ready for reassembly: hold the two halves af the HVAC together and click on the 5 little clips. hold up the HVAC to the firewall inside the cabin, and screw on the finger nut on the right side. Next nuts in the engine compartment and so on. Attatch the "cow horn" system and fasten the two black plastic nuts to the HVAC, so the complete HVAC is now in the car.

24/ Both on the bracket on the floor in the center console, and lift in the dash. Rearrange the wires in their clips.

25/ Is that hard? Here's a few tips:

a/ There are a few wires going all the way from side to side, e.g. doors, speakers etc. These have to be uppermost.

b/ There are wires in the left side around the fuse box. Keep these separate and mount those in the clips.

c/ At the right side, in stall the fan, and click in it's wires, and same for speaker, right side. And lift up the wires in it's clips.

d/ In the middle, behind center console, you have to see through the instrument binnacle hole, and on your right side, there's a few metal bars that gives structural integrity to the dash. You have to lift up the wires so that they steer clear of those metal bars and the center air outlet plastic hose.

e/ In the middle, comes a lot of wires from below/behind. These have to be untangled from the HVAC cables. Look at it as a multi story house with several floors. If you lift up something that is not supposed to be above something else, you cannot. so take your time, and it's not that hard.

26/ Reinstall stalks, the upper steering cover, buttons, HVAC cable control, glove box, instrumentation, instrumentation multiplug and it's little air hose etc. plus the ignition coil and THE VERY important ground cable, mentioned earlier. Now, it's time to put on + plus and then - minus on the battery and test if it all works. You can choose to do that earlier, just for the fan and also listen for 4 speeds of fan, plus listen for peeping sounds from the airflow (at max speed - 4). If there's a sound, look behind each air outlet, from the inside, and make sure each air tunnel is properly attatched - pushed on to the air outlet. This will cure any peeping sound. To gain enough access, you may have to loosen or remove the bolts for the dash once more, Easily done. Retighten.

27/ Reinstall all the plastic parts below the dash, both left and right side, install steering wheel, center it and then reinstall wiper system, then the (d-)rain system and enjoy!

Kind regards,

Redfox 😉

[fendervg 30]

Great stuff - step 13, the 3 bulkhead bolts (although in reality they are shouldered bolts with a shouldered nut and captive washer) is vital - if they spin instead of coming off you may as well give up or allow a full extra day to get them out - you can remove the matrix with them in place if needed, but cutting them off is tricky due to access - in the end I had to jam a hex driver under the bulkhead and use another on the firewall side to break them free. They can be hard to source as well, but are common for all Mk2 cars.

[fla 9]

Great guide. Thanks for taking the time to do.this.

Mine has aircon so is slightly more involved, especially as the wiring was crossed over and a real mishmash!

[Dox 22]

20 hours ago, fendervg said:

Great stuff - step 13, the 3 bulkhead bolts (although in reality they are shouldered bolts with a shouldered nut and captive washer) is vital - if they spin instead of coming off you may as well give up or allow a full extra day to get them out - you can remove the matrix with them in place if needed, but cutting them off is tricky due to access - in the end I had to jam a hex driver under the bulkhead and use another on the firewall side to break them free. They can be hard to source as well, but are common for all Mk2 cars.

Wire brush / lube is a must.

 

No mention of "matrix" in the topic title, that's what people will search for.

 

Thanks for taking the time to write a guide

[Redfox 10]

Right, so is there a possibility to change the title, so more can view it, aka "heater matrix" added?

Kind regards,

Redfox.

[fendervg 30]

If you are the thread owner, go to the first post in the thread and click "Edit" at the bottom - this should let you change the title.

One of the moderators should be able to make it sticky too.

Edited September 13, 2023 by fendervg

[_Matt_ 26]

Edited the title. If i pin it will be in the newbies hangout which i don't think is the right place for it. Are you ok for me to move it to the correct subforum and pin it? 

[g0ldf1ng3r 13]

great post

i do have a full guide with pictures that i send out on request as ive never found how best to upload it here

[g0ldf1ng3r 13]

why id never though of just attaching it lol

always tried to wiki it previously but hey ho

i will have a look at the sticky thing for this post

Replacing the heater matrix.doc

[Redfox 10]

11 hours ago, _Matt_ said:

Edited the title. If i pin it will be in the newbies hangout which i don't think is the right place for it. Are you ok for me to move it to the correct subforum and pin it? 

Yes, please.

Kind regards,

Redfox.

[paddy26 3]

There is a guide on vagdrivers for replacing the matrix without removing the dash:
https://www.vagdrivers.net/threads/corrado-heater-matrix-replacement.19713/

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