Intermittent Or Permanent Speedo Fault, How to fix it

Hi all,

The curse of the intermittent (electronic) speedo has been solved

Please find attached a self-help file on how to repair that annoying flicking needle on your electronic speedo.

Thanks to xmexclusive and Peter. N. for their help and guidance identifying the original fault.

As usual, please report any errors or omissions.

Cheers

noz

Beautiful, clear document. Very nice work. May come in handy some day

Excellent work as usual noz. Thank you for taking the time and effort to put it together.

Ciarán

Thanks for that Noz

You have turned my theory into reality! I still havnt done mine, weather and all that (inclination really). At least I know the easiest way to fix it now, I probably would have tried soldering it.

Peter.N.

I have reactivated this post as I now have the definitive answer (I hope). I finally have a continiously working speedo on the red car. After several unsuccesful attempts at finding the fault, which resulted in a temporary restoration of speedo function, I now seem to have effected a permanant cure.

I was pretty sure that he fault lay with the wiring into the red plug in the instrument panel, as every time I disturbed it the speedo would work for a time and the go intermittend again. Anyway, I have just had another go at it, and all seems now OK.

The problem (in my case anyway) was with the forth wire from the right hand end of the plug as plugged into the board, its yellow or orange (I'm colour blind). I pulled quite hard on all the wires with a small pair of pointed nose pliers and that was the second one to come adrift, I had already soldered one, if you can't pull them out with reasonable force, I think you can quite safely assume they are making good contact.

If the wire comes out, strip about 1/8" of the insulation off, tin the top of the original wire clamp, looks like two loops of wire, and solder the wire on. Give it a gentle tug to make sure it has taken. You will need a soldering iron with a very thin tip. The best way I have found to hold the plug in a workable position is the drop the steering wheel to its lowest and furthest in point and than gently clamp the wires to the plug in a pair of mole grips, having twisted it into a suitable working position, the wieght of the grips will hold it still.

Peter.N.

Hi Peter et al,

Since I posted the self help back in January my spedo reverted to the intermittent failure again. Not wanting to give up I took the instrument cluster out again(for the umpteenth time) and scoured the back of the pcb with a magnifying glass particularly around the red socket. However, I could find nothing amiss. Even with a poerful light and a magnifying glass I couldn't see any hairline cracks in the solder. Unfased, I took a soldering iron and resoldered every connection on the plug. I returned the instrument cluster to the dash and ran around with the front fascia still off for a few weeks. The speedo has never blinked once since I did the soldering trick. I've now reassembled the fascia and all is still well.

My instinct tells me that with so many faulty speedos there must be a common fault but the different methods to fix the problem suggests otherwise. One thing is for sure. The location of the red plug/socket in relation to the metal structure of the dash means that the cables coming out of the plug at 90 Deg to the pcb are badly stressed trying to turn through a further 90 Deg to pass the metal chassis. Any vibration will take its toll on this connection over time.

The good news is that the fix is relatively painless and now fairly well documented. No one need now put up with a faulty speedo.

Cheers

noz

Hi Noz

I had previously fitted three different instrument panels, all gave the same symptoms so barring a very strange coincidence, I think it was the plug connection, especially as it came out when I pulled it. this is the longest its worked so far - only time will tell.

Peter

This weekend I tampered with the faulty speedo (indicating 80 km/h, remaining distance/fuel not working, other computer features fine) and tried to repair the wire/connector contacts but it didn't work out. What should be next: repairing dry solder joints on instrument panel PCB or going down to the gearbox device?

This post has been edited by John Malkovich on June 30, 2008 08:52 am

I don't have the luxury of a fuel computer on mine is it has a mechanical pump, but as the computer relies on input from the speedo sensor to do its job, its highly likely thats where the problem lies.

Peter.N.

I agree with Peter, it's time to get out and get under.

Derek

Hi John.

On mine it turned out to be the sender. Guy at the parts department intimated it was a fairly common failure ---- must be, as they actually had them in stock. Only oddity is that yours continues to give a reading of some sort. On mine, it would work for the first three or four miles, falter, then die. My guess is that as the diff oil warmed and got thinner it found its way into the sender --- but it is only a guess.

Mike.

This post has been edited by onthecut on July 02, 2008 09:05 am

OK, here's the next one: last night I filled the tank to top (which has become a major impact on wallet stability recently) and wanted to begin measuring the consumption in urban cycle. When resetting the analogue trip meter, pushing the button restored the speedo function - alas, only until the next bump, then it returned to 80 km/h. Not every reset push worked. And sometimes even a punch above the instrument panel would work but not always.
PCB, then?

This post has been edited by John Malkovich on July 02, 2008 10:10 am

Hi John

Sounds like a fault on the panel then. Noz had intermittent problems which he traced tp dry joints on the PCB, but on my car it was poor connections to the pins of the red plug on the instrument panel. The best way to check is to remove instrument cluster shroud so you can see the plugs the drive along, pulling on the leads, if that's the problem you should be able to make it go on and off, well on at least. Of course, if the fault is on the panel, pulling on the leads could have the same effect. The only sure way is to substitute the panel with a known good one, that was how I eliminated the panel and settled on the plugs.

Peter.N.

Noz did you do the self help file, if so what did you create the pdf etc as i have a few things i'd like to write up in similar style / file format.

Hi Lez,

I created the original document in MS Word and then "printed" it to the Adobe PDF "printer" which essentially converts the Word document to PDF. There are other, free PDF converters out there. You don't have to buy Adobe Acrobat to make them (e.g. www.pdf995.com).

Hope that answers your question.

Cheers

noz