Faulty Speedo & Fuel Gauge - Solved

[Gibbonius]

Hi All,

I'm more of a lurker but I've been reading since I got my Y-reg Octy back in 2008 and I've appreciated the help I've had either asking direct questions or just reading other people's experiences. Back in March this year my speedo stopped working intermittently. It would either drop to zero, or sweep continuously between zero and the speed I was going (servo location, I suppose).

Some quick searches on here suggested most likely cause to be dry joints, but before the fiancée's Dad (an electriconics expert) could have a look for me, the problem disappeared. Two weeks ago the problem reappeared followed a week later by the fuel gauge dropping to zero whenever I move the steering wheel. Strangely this only happens when driving: stationary with the engine running, dry steering won't affect the gauge. I tried the fuse 15 trick which did nothing. The future-father-in-law had a look at the instrument cluster with the help of za_killer's post. He confirmed dry joints and generally shoddy quality soldering, re-flowed it all, we took it for a test run with no improvement.

We had a chat with more fiancée family who works at a Skoda garage. He said first step would be to replace the cluster, an expensive but by no means guaranteed fix, and the second candidate would be the control unit (with a similar story on price and chance of repair). The control unit is also a likely suspect due to other problems that have emerged including intermittent central locking (with both keys and with fresh batteries), intermittent Climatronic problems, and occasional petrol-style kangarooing under gentle acceleration.

Does anyone have any thoughts on this? This is my first car and I'm rather attached to it; with the history of Skoda Works our nickname for it is The Tank which it's lived up to a couple of times. Is it full of gremlins? Am I to go looking for a Mk2 at the weekend? The only saving grace is that I'm borrowing my brother's car in the interim - a 1st-gen Fabia VRS - my word they're fast fun!

[rwbaldwin]

I would check for a loose earth connection before I did anything else. There is one at the steering column and another next to the relay plate under the dash.

[Chris Coates]

Loose earth does sound like a likely candidate...

[Gibbonius]

That sounds too straightforward to be true, thanks. I'll take a look.

[Chris Coates]

You'd be amazed.

Also... I'd make sure there's no drainage problems. Octys are well-known for bad drainage causing all sorts of mayhem...

...Have the scuttle panel off and make sure the drain holes are clear.

Also... As daft as it sounds - unplug/replug ecu, check the connections, if they look bad clean up with contact cleaner and get some dielectric grease to protect it from happening again.

It may become a case of unplugging each plug one at a time to check and double check all plugs, clean up contacts, and then protect them.

Also...

The fuse panel. A lot of people don't look at the fuse panel as a possible cause - but sometimes the connections going into the panel work themselves loose causing all sorts of problems.

Personally, if it was the ECU that was fried I think you'd be seeing a lot more problems than you actually are - although I could be wrong.

[pauldazzle]

If reflowing the solder joints didn't work one or both of the 2 voltage regulators on the cluster are probably goosed.

Edited 25 May, 2012 by pauldazzle

[pauldazzle]

The Central locking issue is probably the multiconnector in the drivers door being corroded which often causes one of the pins to snap too it's, a very common problem just do a search on the forum.

[Gibbonius]

Both earth connections were firmly fixed but the one next to the ECU connectors was highly corroded, we cleaned off and reconnected to no avail. Checked drainage, all good, but even more convincingly on that point the weather has been good all week so any standing water that was present a week ago will be long gone.

As of this morning odometer, trip and mpg readouts were not working either. We decided to take it down to the family at Skoda. 10 miles down the A1, speedo, fuel, everything goes back to normal which is not ideal for when a technician is about to have a look at your problem. They had a look, no related fault codes or obvious problems. They asked me to swap back to the OEM stereo even though it's been more than 2 years since it got changed. Car fine all the way back except a brief spell of wavy speedo needle. I suppose we'll try fuse panel next. They wouldn't have said it was the instrument cluster.

[Chris Coates]

Really hope you get this sorted mate...

If there's anything we can do let us know. But it sounds like you're doing as much as you can.

[Gibbonius]

Cheers Chris. Oh forgot to mention we pulled the ECU plugs but they, and the pins, looked brand new. Does anyone think that an auto electrician might be worth a try?

Edit - All fuses checked and fine. Interestingly the Haynes manual says fuse 15 should be 10amp and it's got a 5amp... something like that anyway can't remember specifics without it in front of me but basically Haynes says it should be a higher amperage. Other way round I could see the problem but does it matter that I've got a lower one in there?

Edited 26 May, 2012 by Gibbonius

[rwbaldwin]

The other thing I would check is the ignition switch or one of the wires from it. If turning the steering wheel has an effect, then this is a likely candidate.

Does the radio always switch off when you pull the key?

[Gibbonius]

Yep, always turns off.

[Gibbonius]

See the For Sale thread :(

[Lofty79]

I had exactly these problems yesterday!!!!! I had fitted a new clutch, and reinstalled the gearbox, but had forgotten to plug in the sensor half way down the back of the gearbox, it has 3 wires, and my car exhibited all of your symptoms exactly!!! It could have come off, it could be as said dry joints, or the sensor itself, but i am almost certain thios would be the problem.

The symptoms you describe are exactly the same

Dont sell yet, investigate this plug/sensor

Edited 11 June, 2012 by Lofty79

[Gibbonius]

All the symptoms, Lofty, or just the wavy speedo? If you got the dodgy fuel and/or jerky acceleration then its very likely you might just have saved my car! Sadly Blairgowrie would be a bit far for me to drive up and kiss you.

Anyone who knows anything about Ebay - am I able to just cancel the auction? I'd love to be able to investigate this suggestion.

[Gibbonius]

Just went through old invoices. Just over a year ago, the car went in for a service but fault codes showed 18062 - Please check DTC memory of Instrument Cluster, P1654 35-10 intermittent and they replaced the speedo transponder. I know for a fact that the fault code is currently showing up. Does this match up with Lofty's suggestion?

[Gibbonius]

Now this topic from VW forums: Golf Speedo Transponder

This all sounds very promising.

[Gibbonius]

Thank you so much for all the help! We removed and reseated transponder then removed, cleaned and reseated sensor cable. Strongly suspected that its this cable connection that's the problem. It, by design, has no seal and was fairly scruffy as a result. Can't believe I was that close to buying a new car.

[Lofty79]

Excellent stuff, i knew it had to be that it was just too similar a fault for these random things to happen.

Glad it was sorted and for free..

[Gibbonius]

Well I couldn't be happier. I've also ordered some Sugru to seal up and protect the dodgy connection.

If it's possible for a moderator, the topic title could do with being changed to something about 'faulty speedo & fuel gauge' so that it's easier to find for others.

[Lofty79]

you may be able to go back to first post and click "edit"

[Gibbonius]

Needed to use 'Full Editor' that's how I was missing it. We'll all sleep better at night if this thread can save someone else's Octy.

[Longyear]

Nice result! ........ always great to hear a positive ending

[Gibbonius]

Nice result! ........ always great to hear a positive ending

Ah but is it the end? Speedo started waving at me on the way into work this morning.

I have two things that I can think of investigating further. Firstly, the multiplug between the transponder and the dash cable because it wasn't particularly pretty. Secondly, the transponder appears to just 'sit' on top of the spindle that turns inside the gearbox and I wonder if it isn't forming a good contact. Should they be connected more firmly, or is that one as it should be?

[rwbaldwin]

When it's 'waving' at you, does needle jump or does it tend to trail the actual speed and eventually catch up?