Redfox

Yes, please. Kind regards, Redfox.

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

update: So my Corrado G60 is out and about again, spreading terror amongst beemers 😉 I spent some 7 hours mingling with the wireing so it sits nice and well protected. Then the rest is just reassembly. I also took the gauges from my original instrumentation, and installed them into the new second hand instrumentation I bought in Germany. Works fine, and I can retain the 55L fuel gauge, rather than the dreadfull 70 Liter showing on the newer version (sat in a Passat G60). Car is working fine again. I wrote a mini guide to do the heat exchanger job, so take a look at that thread in this same section, if need be. Kind regards, Redfox.

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 😉

Thanks Fendervg. The flaps are very smooth as always. I've greased the cables and their mecs, links etc. I've used a "Nissens" heater matrix. The upper metal frame is 2mm too wide and cannot be sanded down, as it will fall apart. A slight change to the receiving HVAC slot, and it works well, while still holding on to the original one, if I should find such a rare item new. Today I installed a "new" second hand instrumentation from Germany, and it works... sort of.... Some LCD lines are burnt out, and the lighting doesn't work, I'll take a look at that tomorrow. Thank you German seller on fleabay... Not. And the new expansion bottle cannot fit the connector, so I sanded slightly the two pins slimmer and it fits. I absolutely LOATHE non-original spare parts. There's ALWAYS a catch; ALWAYS something that has been made imprecise. Yuck! Engine started up again and seems to run well (as usual). Now, the HVAC is back into the car, and a slow reassembly is going on. Kind regards, Redfox.

The lcd showed lack of some lcd lines. The bulbs were blown, so I inserted new ones. So, funny thing. New earth cable, and voila, the lcd works on all lines. I can only stress that this particular earth going from the ignition coil to top of gas valve, needs to be fresh, not corroded under the black sheath. All okay now. I spent 12 hours today reassembling, as the wireing were messy and I needed to sort that out. Now it sits well as it should. Tomorrow is time for all the interrior plastic and the rain system in the front and the wiper system, fresh air intake etc. Kind regards, Redfox.

Thanks Fendervg. The flaps are very smooth as always. I've greased the cables and their mecs, links etc. I've used a "Nissens" heater matrix. The upper metal frame is 2mm too wide and cannot be sanded down, as it will fall apart. A slight change to the receiving HVAC slot, and it works well, while still holding on to the original one, if I should find such a rare item new. Today I installed a "new" second hand instrumentation from Germany, and it works... sort of.... Some LCD lines are burnt out, and the lighting doesn't work, I'll take a look at that tomorrow. Thank you German seller on fleabay... Not. And the new expansion bottle cannot fit the connector, so I sanded slightly the two pins slimmer and it fits. I absolutely LOATHE non-original spare parts. There's ALWAYS a catch; ALWAYS something that has been made imprecise. Yuck! Engine started up again and seems to run well (as usual). Now, the HVAC is back into the car, and a slow reassembly is going on. Kind regards, Redfox.

Update on the G60 instrumentation: We've now been over every single component and soldering on the whole main pcb + all the components it's possible to reach on the small secondary pcb - no errors. But the same failures. So we concluded, that it's a chip error that is unfortunately non-repairable. I went to VW today and asked for a new instrumentation - nope. nothing, nil. Zero. Not even at VW classis parts. To me at least it's so strange that VW is not proud of their cars, but instead neglecting them largely. So, I bought another instrumentation from abroad, and since there's no warranty and no 100% compatibility, I can only hope it will work. Meanwhile at the garage, I decided to take out the whole dash and the HVAC system and change the heat exchanger, since I drive with the original one and it's 32 years old. That proved to be fun, of course. I noticed that the ventilation flaps inside the HVAC are covered in foam and it-- rots. So rinsed it off and new foam on. then the new heat exchanger didn't fit, as the upper pressed metal frame is 2mm too wide. Oh well, modified that and it now fits perfectly. Glued on new seals and gaskets, and the HVAC is ready to go back into the Corrado tomorrow after work. Kind regards, Redfox.

An update: - The NPN transistor that had a faulty leg has been changed. - The power supplies (rails coming from the input connector is all good. - Some power rails further down the pcb seems to be dead - meaning that they can be traced back to the daughter pcb (the small one) and as a consequence does not power up, until other functions are at play. Therefore there are voltages with around 2 Volt, that are inactive. Or dead, and we didn't find any faults yet... - Most components we have been able to reached are tested and works as intended for value etc. - No shorting out anywhere. - All the solderings on the daughter board (the small one) have been reevaluated, and resoldered, also the hard to reach side. - I need a schematic for the instrumentation! Desperately. I will pay anyone who may have it, a nice sum of money via paypal, if I can have a copy. Mine is a 1991 Corrado G60 (chassis series ...ZMK...), German car originally, km/h, 55L fuel tank, 6200 rpm. Made by VDO, not Motometer. And with the blue adaptor on the back. Kind regards, Redfox.

We've been measuring some of the main pcb and some of the secondary smaller one. - we have resoldered all input connector legs, all legs on the main pcb for the secondary smaller pcb, all legs on top of the smaller pcb, plus a variety elsewhere. After that, we have found the following: - We found that all grounds so far are good. - we found that both power supplies from the input connector are good. We did not look at the 3'rd one, as it's for lighting. - we found that the "voltage regulator" as VW calls it, the transistor, is good at 10,000 Volt. Should be between 9,5 and 10,5 Volt. - we found that there are two more transistors fastened with a sort of double copper spring. One NPN, one PNP. - we found that one leg on the NPN was broken, sitting at 90°, soldered that. It's been replaced before. - we found that measuring the NPN transistor without power attached to the main pcb, from a lab supply, it was fully working. - we found that the very same NPN transistor is unable to operate as it should, because there's +15 Volt, +2,0 Volt and +2,0 Volt. That is too little. 2,0 Volt is probably not used, so something is bad. These 2 Volt is not enough to operate the transistor, so it doesn't function. AS far as I know, no matter the voltage as such, there should be a difference of 0,7 Volt on a transistor. I've ordered a new NPN from Mouser. - we found that the 2 traced having 2 Volt, goes to the smaller secondary pcb, around the area where upon pressing a bit, there's led lighting and strange LCD behavior. Irregularly. - we found that the PNM works fine, and there's 12 Volt, +5 and a little less (I am not sure, as I don't remember by now). --- This leaves us with something to work with. I'd like to know if anyone knows anything about those 2 Volt??? Or does anyone know what voltage to expect at those two legs on the NPN transistor? Kind regards, Redfox

Okay, so no start up routine. Sure it would. There are two other known Corrado's in my country, and one I haven't seen in years, and the other is a VR6 with audi 4 wheel drive and two huge turbos. I know none of them, and they won't be willing to swap briefly. And I think 5 smashed ones, long gone. One was for sale like 4 years ago across the country, but that was with the old instrumentation. I think it was later sold to a foreign country. I only had a moments contact with two owners on the streets and highway, in 12 years. 911? A few of them on every single corner. So buying one is the only option. I want to solve this, rather than buying, as it's much more interesting to solve it. If it turns out fruitless in the end, after much work, then okay. But for now, I want to repair it. And mine has only done 161.000 km. Kind regards, Redfox.

Thanks guys! My friend and I am about to measure every single component on the pcb, check every single soldering pad and trace on the pcb, starting with the small pcb for the MFA. I am also more convinced that this is where the problems lie. But as the two oil and coolant LED's are sometimes provoked to light up, by also pressing on a suspect area of the smaller pcb, it could be somewhere there. Or again on pads and traced that it connects to on the bigger pcb, though all solderings for the small pcb have been cleaned up and resoldered, incl. using flux. By now, most solderings on the big main pcb have been redone. On to the smaller one. Question: Does anyone know if the instrument cluster have some sort of startup routine that it has to pass, before showing normal condition? While I know this is not normally seen, it could be such a thing that it cannot pass because of say a bad resistor or capacitor, so a voltage is not correct for a given circuit? Also: does anyone have a diagram of the instrument cluster pcb? Or a description? I''ll report back on the findings (or lack thereof). Kind regards, Redfox

An update: The main pcb on the instrumentation is now out again. Ground points and main ground points are measured and are fine and with correspondance between them. Pin 1, 3 and 5. So is main +, terminal 31 and 15. The 3'rd + is not used now, as it's only instrument lighting. The main transistor, called "voltage regulator" by VW, is measured to give 10,00 Volt exactly. As it should be within 9,50 Volt and 10,50 Volt, I'd say it's fine. And the voltage is completely stable, with no fluctuations. So 3 wires are soldered on to the two main +'s and the main ground mentioned in the above. That would be pin 11, 13 and 3 respectively. As I understand it, terminal 31 is the main + and terminal 15 is main + via ignition switch. Then the wires are connected to a laboratory power supply, at 12,000 Volt and 65mA max power usage. No turning on. Then voltage is raised to 12,500 Volt and consumption limit is raised to 200mA. Then the board powers on, and with same faults as if it was in the car, as described earlier. Upon pressing slightly on a specific area of the small extra pcb that is soldered on the the main pcb, lines in the two LCD's change to strange lines, and LED's for coolant and oil turns on ireglularly. Okay. Voltage is raised on the power supply to 13,2 Volt and the same happens. Irregularly that is. I'd say the chips MAY be okay, and that it MAY point to a trace or a component unstable or dead. See attatched picture for specific area under suspicion, at tip of cotton swab. No more test for today, but further investigation and testing of traces, components etc. is due asap. Question: Does anyone have a diagram of the instrumentation pcb, in any of it's forms from Corrado, Passat or similar? It would make it more easy to looks for errors. Kind regards, Redfox.

Well, the good looking ground wire from the rain tray (dash?) to the gasvalve, looked fine. I took it off and cut up the black insulation. Rotten as a EC parliament member. I installed a brand new one and result: nope. No go. Same errors: missing led for coolant and oil, missing rev counter and bot LCD's are fully lit with all lines. Hmmm. Everything else in the instrumentation works fine. Everything else on the car works fine. ??? Kind regards, Redfox

Yes, it looks fine. I'll go and inspect more carefully, as the braid (the wide flat wire) is covered in a black sheath. Kind regards, Redfox.