hall sensor (kinda long)

Lean Angle · Post by **Lean Angle** » Tue Dec 05, 2006 12:20 pm

Well, after 4 trusty years and 39,000 kms, my '02 beak's hall sensors went south after a pressure wash (yeah, yeah, yeah, i know). Symptoms were: died after 4 kms from wash, strong crank but no fire, no spark, fuel pump primes normally though, so pushed it home. After repeated tries, she finally started after 3 days only to die 5 sec later (started making grounding/arcing noises somewhere under the tank-left rear, and fuel pump was cycling unusually), and didn't start again. Towed to dealer, she started right up and ran fine there, diagnostic showed no codes though. Picked her up 3 days later, died within 3 kms from dealer, towed to dealer within 2 hours, started right up, no codes again. Left her there for them to check her out again, no problems, runs fine. Picked her up after 3 days, test ride with the mechanic following me. Like clockwork, dies 2 kms later, this time the tach starts dancing on its own. Towed back, plugged into diagnostic while attempting to re-start the bike, still no codes despite the engine refusing to start this time. Pulled left plug, spark. Pulled right plug, no spark. Pulled left plug again, this time no spark. Grounding/Arcing sounds start again from the same location, along with the fuel pump cycling unusually. Lo and behold, suddenly the diagnostic shows hall sensors 1 & 2.

$400+ and 2 days later, a new hall sensor assembly is installed, and I happily (yet heavy heartedly) ride home. New mantra: "Pressure wash... bad!". Anyway, upon looking at the old part, I noticed it was a bit different from the new one they installed. Both had the same BMW part number 12117673277. But the Bosch numbers on the plate were different. The old one says Bosch 0232101034 on the plate. I wasn't able to get the new unit's Bosch number as it was already installed, but I'm at least sure I saw the last digits were different. Another notable difference that I saw was that the old one was just a wire harness straight from the sensor plate all the way up to the connector. The new one had some sort of small sealed black box inserted in the harness in between the plate and the connector. Anyone familiar with this new unit? The connectors are exactly the same though. Anyone have the Bosch number for this new unit? I'm hoping it's an improved and more durable version.

TIA

chris · Post by **chris** » Wed Dec 06, 2006 5:56 pm

Sorry, can't answer your question but wanted to say thanks for stopping me getting the pressure washer out to get the crud off my bike. Haven't washed or wiped it down in a few months and the beautiful shiny thing I bought is looking a little worse for wear. Will do it the hard way...

Post by **challey** » Wed Dec 06, 2006 7:55 pm

I can't answer the question either but the subject got my attention.

Where are the Hall effect sensors located that makes is so suceptible to moisture? And why do they need to be replaced after getting wet (as opposed to simply drying them out?

I understand that you shouldn't use a power washer but I wonder if the sensors can also fail from repeated riding in the wet?

Lean Angle · Post by **Lean Angle** » Thu Dec 07, 2006 2:02 am

I feel a bit better now after going through the 5 stages of DABDA. Was able to get the number for the sensor with the black box, it's 0232101093. Still have no idea what that box is for though, will try to post a pic. My old sensor looks and works fine on the bench. Tried wetting it, still works. But haven't tried heating it yet nor checking inside the harness, so will do so next. Found the Honeywell replacement sensors, but will try rebuilding the harness first with higher heat capacity wires.

Chris and Challey, the sensors are behind the pulley driving the alternator, which is behind the plastic alternator cover. I've read that more often it's the harness that goes bad before the sensors. The constant heating/cooling and age presumably degrades the harness. Once moisture enters, it probably shorts the sensors and there you get the problem. It will probably dry out and start again, but strange why my intermittent problem kept recurring. Come to think of it, it was a good thing the problem manifested itself from the wash, at least it was close to home. Hate for it to strand me in the boonies from riding in the rain. Will try rebuilding my old one and keeping it on the bike as a spare. Maybe with some bubble wrap I can keep it under the seat.

Still wondering what that black box is though.

riceburner · Post by **riceburner** » Thu Dec 07, 2006 5:06 am

What power is your pressure washer??

a high power (2bar or above) pressure jet is FAR more damaging than rain water.

Lean Angle · Post by **Lean Angle** » Thu Dec 07, 2006 6:12 am

Hi Riceburner, didn't ask the Meguiar's shop what pressure their power washer was, but it was a lot weaker than what my bike has been getting at Shell for the past 4 years. Difference was that Shell's blast air along with water mist, Meguiar's was just water spray. will probably just play it safe now and do it the hard way as Chris mentioned

Post by **CycleRob** » Thu Dec 07, 2006 8:07 pm

To me, the water didn't directly kill the hall sensors. The arcing secondary Hi-voltage did. The (?soapy?) water caused a short across the coil tower's insulator and ZAPPED the primary wires (in the hall sensor circuit) with about 30,000 volts. It also freaked-out the Motronic so the fuelpump on-start runtime kept restarting and the tach needle gets jumpy. The Hall sensors aren't designed to, or capable of, resisting that kind of 30KV attack and the electronics were essentially "electrocuted".
Poof!

The dealer tech knows this and hopefully has cleaned and buffed the coil tower where the conductive liquid path was established so it doesn't happen again on a ride in the rain. The coil "tower" is that plastic looking mound the plugwire attaches to - - - - hidden under the fueltank. I believe there is a real danger this will happen again if wetness occurs on the (untreated?) coil tower.

This sort of shorting is not uncommon with mistreated ignition coils and can also happen with open firing the plugwire - - - - cranking the engine for a spark test when the sparkplug plugged into the wire is NOT grounded. BTW, the painted cylinderhead cooling fins are a poor ground!! Use a bolthead instead. The trouble codes were prolly not set until the hall sensors were destroyed, days later.

The next time your bike won't run because the ignition is wet, fix/repair the wetness's conductive path ASAP before you continue to force it to run badly. Did I hit a $400 nerve here?

Post by **challey** » Thu Dec 07, 2006 9:33 pm

OK - you've really got my attention now.
I kinda know how the Hall sensor works, but what does it do on the R? Are these devices commonly used on other reciprocating engines or is this another example of weird German engineering? Are there better solutions than Hall sensors?
Also, when I looked up some info on Hall sensors, one of the statements I saw was

Hall effect devices when appropriately packaged are immune to dust, dirt, mud, and water. These characteristics make Hall effect devices better for position sensing than alternative means such as optical and electromechanical sensing.

If that's true for the sensors on our bikes, then Cyclerob's theory that arcing secondary high voltage across the coil tower's insulator to the sensor makes a great deal of sense. Seems like somthing that a more elegant design could eliminate though.

Post by **TicTac50** » Thu Dec 07, 2006 10:59 pm

Lean Angle. You got away easy for only $400.00
For me, it was $800.00 and I still don't konw if it was the havy rain
or my AirMan compressor that did the damage

Lean Angle · Post by **Lean Angle** » Fri Dec 08, 2006 12:39 pm

Maybe that's what that black box is for? Protection, diode, I dunno. There's a pic on advrider gspot if you're still ineterested.

jamais · Post by **jamais** » Sat Dec 09, 2006 8:13 am

Hall Sensor Course:

http://users.rcn.com/dehager/service/oi ... ensors.pdf