Hello again after years and a problem... ;)

[Redfox 10]

HI all,

 

I have been off the forum for some years, because I also race bicycles and work on building a racecar for the road, climb mountain, build HiFi and a couple of other things. so, I cannot post directly into the subforum. So I'll reintroduce myself. I am Redfox, 55 y.o, and I've been driving and meccin' my Corrado G60 for some 13 years. 

My Rado is a 1991 in red with black leather Recaro, naturrally, and I've been servicing my Rado all the time, plus making some mods over the years, mostly a bit inside the cabin plus underneath.

Well, I only drive it during Summer and only some 5000 km per year, sometime less. It' passed 150.000 some time ago, many services by myself and of course the obligatory sun roof thing, where I changed all 4 sets of spares so it slides perfectly. VR6 center gauges made to fit in the center console. And two years ago, I did another big service on the engine, changing many parts such as sensors, all seals on engine, painting engine block etc,  all sorts of parts underneath in suspension etc, all brackets remetalised, belts, oilpan, servopump, oilpump, waterpump and had the Glader redone for the 2'nd time. Runs smoothly and 0,65 - 0,7 bar boost and is standard - not tuned. 178 Hp with a free flow exhaust and a sportcat. I dyno it every second year before MOT. Adjustable KW's, harder bushings, Eibach strut bar between towers front and rear, plus Eibach arb's front and rear below. Light BBS forged RC's on 215/40-17". Absolutely no rust in the car so far.

When I bought the car, I redid the front seats and installed bigger bolsters from Edition 1 Golf 2 seats, plus inflatable lumbar supports, rare "leather" on handbrake and door handles plus my old Momo wheel and knob, of course. Always been running smooth and powerful. No water use, no oil use, no smoke, no nothing.

Over to the problem: Today, I started the car, and noticed the water warning led flashing. Turned off, checked coolant and that was up to max. Started again, and the flashing comes back after some 15 seconds. Looked at all belts and seems fine and running as they should. I felt at the water hoses and coolant is running. Warms up a bit faster than usual, though I cannot be sure because of outdoor temp. Then I noticed the rev counter is not working... No movement of needle. Car warms up and fans start and cools down as it should, cycling between the two points of temp, which is as usual. I took the connector off of the coolant tank and shorted the plug with a wire. No difference (if the sensor should be dead). The black rearmost sensor on the front of the PG engine I took off, and no coolant needle movement. so back on. All fluids on the car is at level. No strange behavior. No knocking with my hand on top of the instrument board could provoke a reaction from the instrument binnacle.

What to do? I am at a loss here, and any ideas are most welcome. I could really use some help on this one. How does the car get a signal from the engine to feed to the rev counter? I can mec but I cannot find these faults yet. Now it's dark, and I cannot go check the fuses until tomorrow. But everything on the car works as normal, except the rev counter needle and the flashing coolant led.

Kind regards,

Redfox.

Edited August 11, 2023 by Redfox

[Redfox 10]

A small update:

I went out in the dark and looked and tested fuse 16 (instrumentation), and it's fine. No swapping helped either. Relay directly above (coolant related) was in place and looked okay; no rattling.

I cleaned the contacts on the ignition coil and no change. As far as I can see, there's no sensor for revs on the crank, so the rev counter must get the signal from the Hall sensor on the ignition rotor, via that plug there. I'll look tomorrow.

Kind regards,

Redfox.

Edited August 11, 2023 by Redfox

[Dox 22]

Hi, you need to be a paid subscriber to use the whole of the forum these days.

 

I've never owned a G60, but have owned a MK2 Golf 8 valve and I'm sure the dash had an earth point on the engine cam cover or cylinderhead? Should that be the case check for fracture, security and corrosion.

Next I'd remove the dash binnacle and inspect the plugs / wiring etc

[Redfox 10]

Hi DOX,

Thanks for the two good points. I'll do that and report back.

How do I measure the resistance on the sensor in the coolant expansion bottle?

Kind regards,

Redfox.

Edited August 12, 2023 by Redfox

[Dox 22]

You have 2 separate issues, both dash related - the engine runs so the hall sensor in the dizzy is obviously working?

 

It appears you have a wiring or binnacle issue if as suggested the 2 faults occurred at the same time?

 

If you short the 2 pins in the plug that will effectively prove disprove the expansion tank issue?

[fendervg 30]

The test on the tank is worth doing - on my Mk2 I had an issue several times, especially with after market cheaper expansion tanks, that the terminals would corrode and short, leading to a constantly flashing light.

[Redfox 10]

Swapped to a new coolant tank, and the same problem - flashing led for coolant in the instrumentation. So I am now taking the instrumentbinnacle out.

I am not sure, I do think the two problems came at the same time. 

Kind regards,

Redfox.

[fendervg 30]

Could also be an earth problem - if you take the lower parcel shelves off, there are earth points on both sides at the inside of the A pillar - these are worth checking. There is also a voltage stabiliser on the back of the clocks, these are usually something like this, but you will need to check yours for part#:

https://www.mk1autohaus.com/Instrument-Cluster-Voltage-Regulator-Tachometer-Signal-Stabilizer_p_7010.html

Edited August 13, 2023 by fendervg

[Redfox 10]

I took off the instrument multiplug off and looked for bent pins or corrosion. No such thing. Put it back on, and now both MFA lights up everything, as well as left side led's not lighting up - water and oil. Bad thing.

I took the instrument binnacle out of the car, and will take it apart later today and inspect the voltage stabiliser, which I read can burn out or become unstable. Also, there's a 1 Ohm resistor that can burn off, but if that was the case, everything would go in the whole binnacle. My water and fuel temp gauges work.

I looked at the star ground on the left side of the car, under the relay/fuse box. No broken wires, nothing changes if I shaked it a little bit - no changes. Earth point totally fresh and clean. I will look at the right hand side later.

Thanks for the suggestions.

Kind regards,

Redfox.

[Redfox 10]

Okay, so I took off the interror plastic on the right side, and the single brown wire to chassis is clean and fine. THat is to say, I don't know if it's broken inside, and I don't know where it leads to.

On to the instruments.

Kind regards,

Redfox.

[Redfox 10]

Right, I took the instrument cluster (ICT) out and apart. All connections for the multipin connector and the many for the MFA extra pcb, have been cleaned, de-rusted and resoldered. One of the two transistors under a copperspring, have broken leg. Soldered for now as a test, but both will have to be changed. They have their legs best too sharp at 90°, and it shouldn't be that, but a curve. The caps and the voltage regulator (also a transistor) is fine. ICT now reassembled and ready for going back into the car, but it's way too late and dark, so next time in sunny weather. I'll report back on findings afterwards.

Kind regards,

Redfox.

[Redfox 10]

Went to the Corrado this morning and reinstalled the ICT. No changes. There is one small observation though. When I start the car and give a little gas, the rev counter needle will make a small jump or movement.

Hmmm... I don't know what to do next, apart from taking the whole ICT apart again and begin measuring every single component from a-z. That's some hours of work.

I will probably take another look at the wires in the car as well.

Any ideas are most wellcome.

Kind regards,

Redfox.

[Dox 22]

On 8/12/2023 at 5:11 AM, Dox said:

 

 

I've never owned a G60, but have owned a MK2 Golf 8 valve and I'm sure the dash had an earth point on the engine cam cover or cylinderhead? Should that be the case check for fracture, security and corrosion

Have you checked this?

[Redfox 10]

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.

[Redfox 10]

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

[Redfox 10]

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.

 

[Dox 22]

The 30+ year old capacitors would be on my radar as they fail with age - check for signs of expansion? You could try and desolder them to see if features return (before replacing them?) - note the orientation before removal +/-.

 

The voltage regulator is mainly for fuel and temperature gauges, if you didn't have it the readings would differ engine off / engine running due to higher alternator voltage. Road speed is calculated by the final drive in the gearbox, RPMs from the hall sensors in the distributer (so neither affected by voltage surge).

Edited August 18, 2023 by Dox

[g0ldf1ng3r 13]

im not sure if this will help but i will input anyway

the rev needle in my 95 VR6 has played up for many years now & ive had it for about 13 years similar to yourself.  some journeys it works fine, others it kind of bounces high but then slowly falls & others it just does nothing.  sometimes, now less more than often, a light bang on the top of the dash or a flick of a finger on the front of the rev counter would make it behave

long story short, & i am unsure if the issue i have is related to that of yours but I do know that i read a fix on here by KevBacon on here where he either resoldered or replaced a simple component (guessing resistor or capacitor) on the back of the instrument panel

i say it might not help as i read it so many years ago ive no idea where it would be on the forum

[Redfox 10]

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

[fendervg 30]

As far as I know the cluster has no ECU or startup routine - it's fairly basic electronics.

Would it be not easier to get hold of a known working one from a breaker or someone who has a spare and plug that in to rule it out? I guess there might be a chance of damaging the replacement though.

Edited August 19, 2023 by fendervg

[Redfox 10]

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.

[Redfox 10]

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

Edited August 19, 2023 by Redfox

[Redfox 10]

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.

 

 

Edited August 29, 2023 by Redfox

[Redfox 10]

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.

[fendervg 30]

I think someone else on here had the same issue with a heater matrix not fitting, being a little too tall - what brand did you use? Also make sure the cables that operate the flaps move freely and don't have any kinks in them - a little bit of PTFE lubricant can help. The cable housings will have a sharp curve on them when fitted, wich makes it harder to operate them.