Do you have a cleaning agent recommendation? Does electrical contact cleaner remove water corrosion (calcium?)?

Duh. I'm too old to be familiar with non-color-coded resistors. I guess 220 is 22 ohms.

If the navi is working, whatever cleaning procedure is applied will likely cause the intermittent connections to go open circuit. In other words the navi may not power up again. You will be left with that sinking feeling which comes when a very valuable item is destroyed accidentally. So plan what to do if this happens and don't panic.

Avoid contact cleaners!

But in case you really want to clean these oxides away....use a glass fibre based "pencil" type cleaner available from all good electronics shops. Use it very lightly on the components, clean away residues with a cotton bud dipped in acetone or isopropanol.

Guys, just to show you how important it is to inspect your navs for water ingress, take a look at what landed in my hands for repair.

Owner's complaint was system not working.

Amazingly, no obvious external water marks.

You have to break the warranty seals to inspect it properly, so if it's out of warranty do it.

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I have a dead MK3 computer navigation with red LED flashing, but that's all that is doing. It accepts a CD, spins it, and after approx. 20 seconds it stops. After normal ibus timeout, the red led powers off. I've tried to diagnose it using navcoder, but there's no activity on IBUS, although, any commands sent wakes up drive like in normal operation. My previous MK3 died after a battery swap, but in that case the red led was off, only eject light was lit according to ibus activity.

As far as I've seen, there are two processors / microcontrollers on MK3 drive...one BGA and a C161 family Infineon uc. Infineon mcu is on a separate mini-PCB that plugs on the MK3 mainboard. I guess this is the protocol converter (among other things) that hooks up navigation computer with bmw electronics. Navbus and ibus signals connects to C161 through bus transceivers elmos 10020 (or E910.05). C161 has 256k onboard ROM and as far as I can see, there's no eeprom/flash/rom externally connected to it. If my MK3 have the power activity flashing, returns normal to standby, wouldn't be possible to have the internal ROM of C161 corrupted? And if so, how can we flash such a device?

could a dulll screen with no backlight be caused by the same problem anyone? i can see the screen in the day time but its pitch black at night

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x5 is gone

The nav powers up on ibus activity - but that is a purely separate circuit that has nothing to do with having any valid operating system loaded.
You can verify this: connect the nav to NavCoder, then send ibus messages that have nothing to do with the nav, eg: IKE asking the LCM for device status. Note how the nav wakes up and powers up on this message, even though the message content is not for the nav. this is proof that it is simply data activity on the bus that powers up the nav, not actual data content.

Anyway, it is highly likely that you have a faulty laser.

You have probably sent the nav an OS-load command, in which case the nav deleted the old OS and is now trying to load a new OS.
But if the laser is dead, it cannot read data from the OS CD, so the loading process stops.

The basic "bootup and load from CD" code still appears to be working, because it is trying to read the OS CD.

And because the old OS is deleted, you cannot do anything more with the nav in the current situation.

Solution: fit a new laser or new drive mechanism.
Or if you have another "dead" Mk3 (ie: the one that died after a battery swap), fit the drive from the dead Mk3 into the Mk3 you are trying to fix. The drives just plug in, they are easy to exchanged (but be gentle - watch the connector locking tabs!)

Then, with a working drive & laser, you can load the OS.

Once the OS is loaded, try the old drive again and see if you can read a map CD. If you cannot, it confirms the laser is dead. You can then repair the old drive with a new laser (or entire new mechanism, because if the laser died, then the mechanics of the mech have already undergone many thousands of hours of life, and will also be wearing out...)

Note that with the "dead" Mk3, you can restore it back to life by sending it to the VDO service center in Wtzlar Germany. They can reflash it for you using their factory tools (because your problem is caused by corrupted flash memory)
The price for reflash is around 100 Euros.

As far as I know, noone else has the tools or knowledge to reflash the Mk3 once the flash memory is corrupt.

Good luck!

First of all..thank you for your answer.

I totally agree. I've played with the drive for a while I've became accustomed to some of it's circuits. Although, without documentation it's a slow process.

Unfortunately, in my case, it's not the drive laser. I've tried with a drive from a working MK3, same results. So if it's not a hardware problem, it's about reflashing the drive. I could get hands on a programmer and a tsop adapter. I will also need a working mk3 to extract the flash contents becasuse I don't have any. But that takes time, anyways I'll post if I get positive results.

Wetzlar does the reflash and also autotronics in Australia.

Problem solved. I've manually reflashed a dead MK3 drive and it worked! I even update to the latest version using Software CD. Actually, I've reflashed 4 units until now with no problems whatsoever.