228 mph Corrado?

[aclwalker 3]

Here's a genuine photo of my dash display showing my average speed on the MFA at 228mph. Sorry it's a bit grainy but it was taken on my old phone.Image000.jpg[/attachment:h5w8rjgz]

 

Before I stopped to take the picture it was at 240mph!

 

I don't have a rocket attachment on my Corrado. This is due to a fault in my dials which makes the clock run less than 20% of the speed that it should (it varies). [strike:h5w8rjgz]It used to only run slow when the ignition was off, making the clock go out of sync. But now it's slow all the time. I think it almost stops when the ignition is off, however, because my MFA1 sometimes doesn't reset at all, even if not driving the car for a week. It's supposed to wipe MFA1 after 2 hours or something is it not![/strike:h5w8rjgz] Scrub all that. I just went out and tested it again. It is working perfectly when the ignition is off, and when the ignition is on but engine off. When I run the engine the clock runs at quarter speed (i.e. it takes 4 minutes to tick over 1 minute). I'm sure it has sometimes run slow when the ignition is off too, as it hasn't cleared the MFA1 over a long period of time, but it doesn't seem to be doing this now. See the post further down for more info.

 

MPG calculations are obviously fine but the time-based calculations are totally wrong! :lol:

 

Anybody got any ideas what's causing this? Is it something I could replace in the clocks? I bought a spare clock on Ebay ages ago. Perhaps I could swap the duff component out of that into my clocks? I'd prefer to keep mine in it for the accurate mileage (high) which I'm quite proud of.

 

Note the coolant temp at about 85C since I fixed all my cooling issues in the summer. The cold weather is helping out too just now, though!

 

BTW, posted in "General Car Chat" because it's an interesting photo, hopefully!

[Timbo 0]

If there is a quartz crystal on the PCB, it might be worth replacing it. Most digital clocks use such a crystal to keep time (http://en.wikipedia.org/wiki/Crystal_oscillator). Usually they're packaged in little tin cylinders.

[iow_corrado_g60 0]

Mate the old girl is going well at 204,000 miles

[aclwalker 3]

If there is a quartz crystal on the PCB, it might be worth replacing it. Most digital clocks use such a crystal to keep time (http://en.wikipedia.org/wiki/Crystal_oscillator). Usually they're packaged in little tin cylinders.

Thanks. I'll have a look on the spare clocks I've got and see if I can locate it.

[aclwalker 3]

Right, I've taken apart the spare dash clocks I've got and located the voltage regulator. It was quite easy to do. I should write up the dismantling procedure.

 

There's an crystal oscillator with the following written on it:

 

6.2914

NDK 23:

 

The voltage regulator says:

 

23BY

LM2940T

-10 I496

 

The voltage regulator seems to be on some sort of heatsink.

 

Now, I remember a while back noticing on vagparts.com that they sold a voltage regulator and I remember emailing the guy about it. It was described on the website as "Voltage regulator chip for the dash clock and gauge supply.".

 

I emailed him about it and he replied saying that "this item is normally used to drop the supply voltage for the dash to nine volts". The only fault with my dash display is the speed of the clock. 30 minute journeys appear to have taken only 5 minutes, for example. Everything else works fine, including the speedo, rev counter, and all the function of the MFA except for those that are time-based, e.g. length of time running and average speed.

 

I've checked VAG-COM and the voltage regulator is listed as a separate part with number 357 919 803. vagparts.com said it was about £6.

 

I've googled for that part number and came up with this link:

http://altrom.com/partdetails.jsp?id=18655

 

The pictures looks very like the regulator but with straight legs.

 

So, could anyone with a bit of electronics knowledge answer these questions?

 

1 Is it likely that this voltage regulator is for all the instruments, or just the clock, given the comments I got from vagparts.com some time ago (above)? Also, remember everything in the cluster works fine, except for the time-based functions.

2 What's more likely to have failed here? The voltage regulator or the crystal?

3 Is there any obvious evidence to look for to diagnose a failed crystal or a failed regulator (bear in mind I've only dismantled a spare working cluster so far)?

 

Any help greatly appreciated.

[MonkeyVR6 0]

I really hoped this would be a video of a Corrado doing 228mph :sad:

[aclwalker 3]

Hmmm, this is weird. I just went out and took the cluster out and checked the regulator on it and it doesn't look burned out or anything. You can see the regulator from the back without totally dismantling it.

 

However, I tested the timing with a stopwatch there and it is running in perfect time when the electrics are off and when they are on but engine not running. As soon as I turn the engine on, it runs at quarter speed, i.e. it takes 4 minutes to tick over 1 minute. I turned the engine off and it went back to working perfectly again, whether the electrics were on or off. Turn engine on and it's quarter speed again, and so on.

 

Could this be a problem with the voltage regulator on the alternator?

 

I measured the voltage at the battery with the engine running and it was 14.10V and quite steady. I couldn't test what it does when I hit the throttle as I was there myself. With the engine off the battery is 12.68V.

 

Is 14.10V too high coming out of the alternator? Could this be screwing up the instrument cluster clock?

[aclwalker 3]

I really hoped this would be a video of a Corrado doing 228mph :sad:

Ha ha. Sorry. I wanted get attention!

 

Maybe somebody could move this post to one of the technical forums now that it has morphed into another quest for help. I meant to just post the picture for a laugh at first but then got annoyed again at this old problem of mine.

[aclwalker 3]

I meant to say. Perhaps I need to just connect up the spare instrument cluster I have and see if I still have the slow clock problems. It's getting dark now though, so I'll need to try that another time.

 

If the spare cluster has the same problem then I guess the problem must be somewhere else.

[Andi 2,147,483,647]

14.3V from an Alt is normal.

[aclwalker 3]

14.3V from an Alt is normal.

Is 14.1V too low then? Like I say this was at idle, with no electrical consumers on. I couldn't test what it goes to when revving because I was alone.

[Andi 2,147,483,647]

No, it's fine. All alternators put out around 14volts.

If you were getting high 12s, I'd worry. 14.1V is perfectly fine.

 

Could it be an earthing issue perhaps?

Just an idea...

[fla 9]

there is an LM 2940 CT in Maplins, is this the same part, ie does the 'C' have any significance? Might need to replace mine too s my clocks give too high an oil temp reading