RevCounter strangeness

[riceburner]

Noticed this morning that my rev counter was behaving very strangely.

I was just making a 5 minute run to work (going shooting this afternoon), and realised that the revcounter needle was pegged at the far end of it's sweep - ie against the peg!

When I got to work and turned the key off the needle only returned about 10 degrees - it's just over one of the warning lights - ie still way off the measured range.

The bike was running ok, so I can only assume something weird has happened to the circuitry driving the counter itself.

This weekend I was messing about with some of the wiring - mainly the accessories wiring that's on the bike.

I have 2 accessory circuits on the bike - both running through relays, with a switch on the low-voltage side of the relay (both are PIAA lighting harnesses). The high voltage side of these are wired directly to the battery, AT the battery. The Low voltage side of each is powered by taking power from the instrument lighting circuits - one from the high-beam indicator light circuit (for a PIAA extra light that can only be used with high-beam), the other is attached to one of the other bulb circuits - IIRC it IS one of the rev-counter bulb circuits.

The things I did at the weekend included repairing a loose connection (corroded terminals) in that second low-voltage line.

What confuses me though is : why would the bulb circuit affect the rev-counter circuit itself??

Does anyone have a wiring circuit diagram for the Rockster instruments?

[riceburner]

I've found these diagrams for the R1100S (similar instrument package), but can't find the rev-counter bulbs. Also there's only 1 mention of the 'tachometer'

http://www.turboferret.co.uk/vehicles/R1100swiring.php

[sweatmark]

Send me an email for attachment.

[riceburner]

Send me an email for attachment.

Cheers!

[riceburner]

Ok - so I had a look around at the wiring last night, everything seems ok.

I even went into the back of the instrument panel and disconnected every wire one by one to see if the tacho needle would move.

Nope.

Then I disconnected the entire instrument panel from the bike :


As you can see - all 3 instrument panel connector blocks are disconnected (including the 2 wire black block at the base of the photo.) Note the tacho needle position.

It's NOT a rogue signal from the bike to the tacho. The tacho has presumably shorted itself or an internal component has fused!

Now that I'm satisfied that the battery is not being drained by a rogue signal within the wiring - I'm ok to leave the tacho as it is. Obviously It'll need to be replaced eventually, but I know the bike well enough that I don't actually look at it that often.

[sweatmark]

'Burner-

Disconnecting the tachometer power from back of instrument will help prevent parasitic battery drain if the tach is wonky.

The SLP electrical schematics show tach signal source to be the trigger/ground of secondary coil. That suggests the tachometer input pin has pull-up resistor, and could be -depending on the tach's microcontroller type - be damaged by inadvertent +12V.

Guessing that the tach drive daughter board is universal for R1150 bikes, although the R1100S/Rockster warning LEDs are unique.

Might be worth the effort to disassemble the instrument module, pull the tach needle, examine tach board, reassemble with needle in mid-RPM position to see if there's any tach function.

[riceburner]

'Burner-

Disconnecting the tachometer power from back of instrument will help prevent parasitic battery drain if the tach is wonky.

I'm contemplating it - but I don't think it is actually drawing any power when the bike is 'off' - I think the internal circuitry in the tacho itself is somehow damaged and it's misinterpreting the signals it's getting when the ignition is 'on'.

The SLP electrical schematics show tach signal source to be the trigger/ground of secondary coil. That suggests the tachometer input pin has pull-up resistor, and could be -depending on the tach's microcontroller type - be damaged by inadvertent +12V.

think you've lost me a bit there...

Guessing that the tach drive daughter board is universal for R1150 bikes, although the R1100S/Rockster warning LEDs are unique.

Might be worth the effort to disassemble the instrument module, pull the tach needle, examine tach board, reassemble with needle in mid-RPM position to see if there's any tach function.

I'm thinking I'm going to try to get a 2nd hand instrument panel from the 'bay of E' and cannibalise the tacho from it.

[vwdoctor]

Sweatmark is itching to dig into that cluster.

[riceburner]

Ok - so - for reference: I spoke toa BMW tech on Saturday and described the issue. He'd never seen it before and was adamant that it wasn't a notification of something from the Motronic.

It would appear that the rev-counter has just lunched itself. (I guess everything fails eventually).

I can live without it - but I'll be starting to look for a cheap set of instruments to cannibalise (don't particularly want to lose my speedo and the odometer reading ... )

[sweatmark]

Burner,

Check out this R1100S topic in Pelican:

http://forums.pelicanparts.com/bmw-r110 ... -here.html

Perhaps your tachometer needle simply needs to be put in its proper place.*

* I sometimes feel that way about my teenager.

[riceburner]

Burner,

Check out this R1100S topic in Pelican:

http://forums.pelicanparts.com/bmw-r110 ... -here.html

Perhaps your tachometer needle simply needs to be put in its proper place.*

* I sometimes feel that way about my teenager.

Cheers for that.

I'll probably dig into the tacho at some point - got too much riding to do at present!

[riceburner]

Burner,


Perhaps your tachometer needle simply needs to be put in its proper place..

Just a quick update - this was indeed the fix! I was fettling the bike and realised I needed the rev-counter to do a TB balance, so thought I'd at least attempt a fix on the rev-counter, so I eased off the instrument cover and flipped the needle back over the pin. Rev counter is now working perfectly again! I guess it must have been jarred over the pin when I had the fall in may/june (whenever it was) and I didn't notice it immediately.

Oddly - When I next used the bike I realised that I'd become accustomed to NOT having the rev-counter and found it slightly distracting! I'll get used to it again I suppose.

[Rocky rider]

Just love a happy ending!!

Well done.