Shift light glowing slightly - SOLVED!

david jenkins · Post by **david jenkins** » Wed Apr 18, 2007 7:45 pm

This may or may not be a bug... could be a construction or installation fault...

Just been out for an evening drive, and noticed that my shift light LED is glowing slightly all the time. The system is now on V3.2.1 and is running well, and the shift light works when it should.

It's just that the slight glow is very annoying!

cheers,
David

Post by **brentp** » Wed Apr 18, 2007 7:53 pm

weird! does it happen on the other outputs as well?

david jenkins · Post by **david jenkins** » Wed Apr 18, 2007 7:58 pm

I'm not using the others!

One's enough for the time being...

Post by **brentp** » Wed Apr 18, 2007 9:56 pm

Well... you could switch your light to one of the other outputs temporarily.

david jenkins · Post by **david jenkins** » Thu Apr 19, 2007 10:39 am

You wouldn't believe how hard it is to muck around with the wiring on the MJ unit in my car. I've fitted it on the firewall behind the instruments to keep it away from rain and engine fumes, and getting to it requires the removal of the dashboard! Serves me right...

As for the problem: it's only visible after dusk, as it's only a faint glow. I think that the problem may also be intermittent, but that's hard to prove as I rarely drive it outside daylight hours. As LEDs usually require a minimum voltage to light up, and then it's usually a significant glow, so I'm wondering whether it's getting a pulse waveform somehow - but that's pure guesswork.

I have the correct resistor to limit the current, but it is a high-efficiency LED - would that make a difference?

The investigation continues...

David

hammy · Post by **hammy** » Tue May 01, 2007 10:08 am

I have a glowing shift light too - it flickers dimly. It is only on one output (I use four outputs to drive LEDS). Because it flickers I've put it down to some sort of noise problem - I don't *think* its related to RPM ( the output supply transistor must be switching ?) ; I do not have a capacitor on the supply line ( as seen on on some installation drawings)..

probably easily fixed with a "MJ" sticker ... er .. cough.. Brent

david jenkins · Post by **david jenkins** » Thu May 03, 2007 3:26 pm

I've spent some time trying to analyse this problem. The additional info I can provide is:-

1. The shift LED is flickering, rather than 'permanently on but dim'. The flicker is fast, such that it's quite hard to see - but it is there.
2. The glow is intermittent - it doesn't show when the engine is first started, but appears at some undefined time later (maybe after 1st shift signal?).
3. The glow does not appear when the ignition is on and the engine not running.
4. The engine is running well, with no sign of misfire or similar problems.
5. The shift light works correctly at the appropriate rpm.

The thing that does come to mind is that I didn't see this problem in the previous firmware release (pre-v3.2.1). Trouble is, I can't remember which version I was running then (I think it was v3.0.0).

It's still a trivial issue - but now that I know it's there...

cheers,
David

Post by **brentp** » Sun May 06, 2007 7:14 pm

While I may appear trivial I'll still try to recreate it myself.

If you collect any more data points or have more insight, please let me know.

Thanks,

david jenkins · Post by **david jenkins** » Tue May 08, 2007 1:03 pm

Thanks Brent, much appreciated.

I'll try and do a bit more investigation soon - but it's raining at the moment, the forecast says wet for the next week, and my car has no roof (or windscreen).

cheers,
David

david jenkins · Post by **david jenkins** » Mon May 28, 2007 3:14 pm

A bit more info:

No glow at startup, first proper shift-light-up doesn't cause it, but seems to appear over a matter of 20 minutes or so.

If engine turned off, then re-started, the sequence is restarted (no glow, then it appears over time).

May or may not be helpful...

Post by **brentp** » Mon May 28, 2007 4:52 pm

Strange! So it appears over a period of time? does it suddenly occur or does the glow gradually increase in intensity?

I'm still working on re-creating this problem, keep an eye on the thread for my findings...

Thanks for the update, David.

david jenkins · Post by **david jenkins** » Mon May 28, 2007 6:21 pm

It's had to give a definitive report, as my eyes are otherwise occupied during testing!

It's off when I start the car, is still off a few minutes later, and maybe 10 - 15 minutes later it's glowing. Last time I tried it I deliberately didn't get up to the rev limit to see if there is any difference - it seems to behave the same whether the rev limit is reached or not.

I'll keep playing, though.

BTW - Hammy - is this the same behaviour as you saw?

hammy · Post by **hammy** » Tue May 29, 2007 2:37 pm

Not quite the same as mine -mine is there all the time from startup . It is on one output LED only ( notably the red one -which I'm guessing is the most sensitive in terms of light output/mA, other drive white & green leds and could have the same effect ,but i don't see it) and is a dim flickering light, something like 10hz - not rpm dependant. My thoughts are that it is noise causing the drive transistor to switch on for a short period of time giving a dim output.

Note i have correctly wired and screened TPS and crank sesnor -I do not having any capacitor on the 12v line.

I've got used to it now and its my "MJ working ok" light

david jenkins · Post by **david jenkins** » Fri Jun 29, 2007 8:02 am

I rewired my shift light over the weekend - gone from 1 light on the dash up to a full set of programmable outputs (5 lights) on top of the steering column. None of them glow unexpectedly when I'm out driving!

I believe that the problem is to do with the length of wire used to connect the LED to the MJ unit. Originally the wire was 4 or 5 feet long and wrapped into the dash loom. Now the LEDs are connected using just 1 foot of wire each, running separately from all other system wiring. I suspect that the original wire must have been picking up some unwanted signal.

Perhaps a small capacitor from 'LED live' down to chassis might be the solution? I'm no longer in a position to test this though.

cheers,
David

Autosport Labs

Shift light glowing slightly - SOLVED!

Shift light glowing slightly - SOLVED!

shift light glowing

Bit more info

shift light glow

Problem's gone away!