Failing instruments in 1999 Octavia 1,6

[Turboman]

In an Skoda Octavia 1999, with the 1,6 litre engine, I have come up on a problem with the instruments, all, speedo, rpm, temp and fuel, drop to zero from time to time.

I have removed the cluster and resolderd what i think is an regulator, that is situated in the top left corner of the circuitboard, after that it worked for about 20 minutes of driving, and i was happy that the problem was gone, but the next day the same thing happens again, turn on ignition, after about 5-10 seconds the needles drops to zero.

Any ideas of what the problem might be ?

Best regards

/Mats

[Sampolainen]

Common fault. Use search to find a solution. Usually new a new cluster is suggested. Otherwise, removing a fuse(can't remember the number) will bring back your instrument panel but as I remember, there were some drawbacks to this solution.

I also remember reading a long time ago about a guy who solved the problem like you did at first. The regulator was the cause to this fault. It gets too hot for its own good. IIRC someone suggested putting a heatsink on it. HTH

[shark_90]

Fuse 15 is the one to remove but it is not a permanent fix unfortunately :(

[rwbaldwin]

Normally, you have to replace the regulator - not just resolder it.

Another common problem is poor soldering of the connectors, so it is worth resoldering these.

[Turboman]

Normally, you have to replace the regulator - not just resolder it.

Another common problem is poor soldering of the connectors, so it is worth resoldering these.

Where can one get a new regulator ?, I guess that the average Skoda parts dealer will look like a question mark if I come in and ask for a "Voltage regulator" to solder into an circuitboard in an instrument cluster, here in Sweden "Authorized Dealer and Garage" means a place where they swap parts randomly until the problem is solved and then print out an invoice with many zeroes in the end, not a place where one would meet a person with knowledge and skills.

Is it a standard circuit, one that ELFA, or Farnell might have in stock ?, that would be super, and if the reason for it´s failure is heat, then one might consider putting a heatsink on it like someone suggested, or is it possible to put an heatsink on the one in the car and get it working ?, as I was fiddling around and trying to provoke the fault to show it self, I noticed that if I put my finger on the regulator, the instruments started working almost every time I did that.

/Mats

[rwbaldwin]

First thing I would do is resolder the connectors. The cables that plug into the cluster can vibrate causing the solder connections to crack and become dry. If it is bad soldering pressing on the circuit board is a good way to check - maybe pressing on the voltage regulator does the same.

If it is the voltage regulator you may be able to find pin-for-pin replacement. If you can't find a pin-for-pin replacement then IIRC you can use a 78 series voltage regulator and use a piece of wire to take care of the different pin-out.

It's been a while since I have done one of these. If you tell me what the current voltage regulator is I will be able to help more.

And yes, a simple heatsink and thermal paste is a good idea

[kynastonp]

Google Translate

the site linked to above suggests that the problem is not the regulator but the resistors underneath it

[rwbaldwin]

In my experience faulty resistors are fairly low on the list

1. Bad soldering - usually around the connectors - vibration of the cables makes the bad joints go dry.

2. Regulator

3. Broken tracks on the PCB - usually around the connector and the regulator

4. Capacitors

5. Something else (including resistors)

I fixed a batch of 20 of these about 3 years ago. All but 1 could be fixed.

After the first few, I just replaced the regulator and capacitors. Then I checked the solder joints and tracks around the connector and regulator. If I was unsure of a solder joint, I just reflowed it. If a track was broken, I flowed it with solder.

I did find one bad resistor but as the regulator had also gone I have no way of knowing if it was cause or symptom.

ps/

I have just checked. If I had any regulators left over, I can't find them now.

[Turboman]

Update:

Today I had another go with the problem, guided by the pictures on the Russian forum, I took it all apart.

First I resolderd the connector (the blue one), then all the resistors and other components around the regulator, I also changed one of the capacitors that I thought looked a little bad (swollen).

After reassembly and a few adjustments of the needles, i drove the car for about 30 minutes, no problems at all, so I hope it´s fixed now, it´s not my car, so I will get a report from the owner on monday if it has continued working.

The Regulator is a Siemens TLE42766, I haven´t been able to find a place where I can buy one, but if the problem comes back I will have another go at finding a company that sells them in small quantities (the ones I found today only sold them by hundreds or more).

/Mats

Edited 31 August, 2009 by DGW
No need to quote previous post.

[rwbaldwin]

Great news. You say you had a 'domed' capacitor, so my guess it was that.

From memory, that regulator is a low drop-out, 10V positive regulator. I know at least one person who used a 78S10 regulator (Not LDO) and has no problem despite a minimum input voltage of 12.5V.

A better solution is the L4940V10 which is LDO and is good down to 11V. These are commonly used in TVs.

You can buy them for less than £2 from Vision Aids

A datasheet can be found here

It may need the pins swapping around, but it will do the job.

[Turboman]

Thanks for the link to Vision Aids, Farnell and ELFA didn´t have it in stock, and Vision Aids delivers throughout europe, so that is perfect for me.

Forgot to mention that I put on a small "cooling device" too, I didn´t have any real cooler for the regulator, so I put a pice of rather thick aluminium plate on it instead, and fastend it with some chemical metal.

/Mats

Edited 31 August, 2009 by DGW
Redundant quote deleted.

[rwbaldwin]

If you put a heatsink on the regulator it is ESSENTIAL that you glue it to board. Otherwise, it may vibrate and over time will break the solder connections/tracks.

[Turboman]

Done that, secured it with melting glue (don´t know what it´s called in english), so it won´t vibrate loose

/Mats

Edited 31 August, 2009 by DGW
Quote deleted.

[soviet]

Google Translate

the site linked to above suggests that the problem is not the regulator but the resistors underneath it

Hi kynastonp;1794054,

My son already did translation for this one, as is the link and date. And so see this here:-

http://briskoda.net/octavia-i/russ-english-instrument-help-us/154674/

Is this by a co incident now, that you also have seen this? This was done last week!!!!!!

Soviet:thumbup:

Edited 29 August, 2009 by soviet
Hijacking of thread here!