Jump to content

Funky signal relay


bwr

Recommended Posts

Just got back from a trip during which my right-hand signal light ocassionally flashes REALLY quicky (not all the time -- sometimes it's normal). I'm assuming this is a realy problem. What do you think?

 

If so, where's the relay located? I was looking through my Clymer and it's not much help, but it seems to indicate that I need to pull the tank to get to it (arrghhh!). Is this correct?

 

Are there any non-BMW (i.e. inexpensive) relays that I can get at an auto parts store that will fit my '04 RS?

 

Thx!

Link to comment

That sounds more like a bulb on the way out than the relay. Next time it flashes fast, look to see if both front and rear lamps are flashing.

 

Andy

Link to comment

Well a bulb would be a lot easier to change than a relay! I did check when it was flashing nomally and they were both going, but haven't checked when flashing quickly. I'll check it out later. Thanks, Andy.

Link to comment
ShovelStrokeEd

The sockets on the BMW turn signals are real crap. I have had 4 of the things oxidize the positive contact so badly it would no longer conduct to the bulb. Good news is you can buy a replacement of equal or better quality at almost any automotive parts store. A little fishing of wires and maybe a butt splice or so and you'll be back in business.

Link to comment
Well a bulb would be a lot easier to change than a relay! I did check when it was flashing nomally and they were both going, but haven't checked when flashing quickly. I'll check it out later. Thanks, Andy.

 

No worries, the relay is about the same or easier to change than the bulb(s). The T/S relay is located in the fuse box under your seat. Refer to your owners manual for which one it is, but it's the big black relay that pulls out towards you with the wiring attached. Slide the lock clip and the connector will release from the relay. Voila! clap.gif

 

But, it's probably a burnt out bulb as stated, especially if it's only happening to one side....

Link to comment

IF the bulbs are working when it flashes fast AND it's happening on both sides, you may have the same problem I had. Otherwise, what the other guys said is more likely.

 

My signal lights were all flashing (albeit fast) when this would occur to me. In trying to discover the problem, the lamp sockets were cleaned and wires soldered directly to the sockets. When it continued to malfunction, I got a new flasher unit. Still no joy. Began to notice it would happen more often when all of lights and heated grips were on. The solution for me (much to my amazement) was to replace the battery. Have not had the problem since replacement. This would seem to indicate that it is possible for a low voltage condition to cause some strange flasher behavior. Please let us know what you figure out.

 

Link to comment

I was asked to report back on my signal light flashing quickly. Basically, since I posted the problem on this forum it's been functioning correctly eek.gif If only it was so easy to fix everything that might go wrong!

 

One point I didn't mention when I first posted this is that the intermittent malfunction ocurred right after I rode through a torrential downpour. It continued for about 3 days afterwards. I suppose it's possible that some water got into the bulb sockets and was shorting something out.

 

Anyway, I'm just going to leave it be unless the problem comes back.

 

Thanks again for your help. At least I know where the S/L relay is now smile.gif

Link to comment
IF the bulbs are working when it flashes fast AND it's happening on both sides, you may have the same problem I had. Otherwise, what the other guys said is more likely.

Exactly! The turn signal relay has no way of "knowing" whether your left or right signals are on. So if it happens on one side and not on the the other, it has nothing to do with the flasher relay.

Link to comment
IF the bulbs are working when it flashes fast AND it's happening on both sides, you may have the same problem I had. Otherwise, what the other guys said is more likely.

Exactly! The turn signal relay has no way of "knowing" whether your left or right signals are on. So if it happens on one side and not on the the other, it has nothing to do with the flasher relay.

Guess you lost me there (only had one cup of java so far). The turn signal flasher module IS connected separately to each "side". The way that flasher modules detect a burned-out bulb (or bad connection, etc) is to sense a lower than expected current condition. A lower than expected current CAN be caused by the module itself (bad output transistor/microprocessor, etc).

 

There are a lot of parts in a the module that can go bad. I posted my findings on the inner workings of the module here: http://bmwsporttouring.com/ubbthreads/sh...true#Post611029

 

So, unless I’m missing something, it’s not possible to state absolutely that it’s not the flasher module, it’s just unlikely.

Link to comment
So, unless I’m missing something, it’s not possible to state absolutely that it’s not the flasher module, it’s just unlikely.

You are right. Because of BMW's oddball signal actuation, their bike signal system is unlike the normal one. I was thinking of "normal" signal systems.

 

Normally, the left side or the right side signals are connected into the flasher "relay" by the switch on the handgrips. You manually make the connection just like when you move the signal lever in the car. In that case, I was right... the signal "relay" has no way to know which side is actuated.... it just flashes whatever set of lights are connected to it by the signal lever.

 

But looking at the schematic of my K100, the signal "relay" in BMW bikes is more complicated. It has 2 actual relays inside. One is actuated (by turning on, then off, then on, then off etc.) to make the right side lights flash. The other relay is actuated similarly for the left side.

 

All this added complexity is needed, because BMW bike signals are actuated by MOMENTARY switches, one for right and one for left. The switches only make contact for the split second you push them, which triggers the electronics to flash the appropriate lights.

 

But the basic point still holds.... The flasher can NOT make a normal bulb run at half brightness. As stated above, the current to the lights on the either side is switched on and off (and on and off etc.) by two internal relays.... one relay for one side and one for the other. The relay contacts are either closed or open. There is no "half-on" position in a relay, just as there is no half-on position in a household light switch.

Link to comment
But looking at the schematic of my K100, the signal "relay" in BMW bikes is more complicated. It has 2 actual relays inside. .....

Brian's 2004 almost certainly uses a solid state (no relay) flasher module.

 

But the basic point still holds....

confused.gif

Link to comment
But the basic point still holds.... The flasher can NOT make a normal bulb run at half brightness.

And that's a silly statement to make, as Nevets is trying to point out.

 

Leaving aside all your other assumptions and guesses about the similarities or otherwise of a 1986 K100 and a 2004 R1150, 'cannot', 'impossible' and other such terms are ill-advised.

 

So, if the bulbs only go through the relay contacts (or their semiconductor equivalents), how can the flash rate be dependant on how many bulbs are connected? Hint: current monitoring in the flasher unit -- something else is also in that darned lamp circuit ...

Link to comment
So, if the bulbs only go through the relay contacts (or their semiconductor equivalents), how can the flash rate be dependant on how many bulbs are connected? Hint: current monitoring in the flasher unit -- something else is also in that darned lamp circuit ...

Exactly. Typically it is a reed relay as I mentioned earlier. Current on its way to the lamps first passes though the relay coil. If the lamp current is less than a predetermined level, the reed switch does not close, and this signals the electronics to increase the flash rate to emulate what happens if an electromechanical flasher were used.

 

As for semiconductors used instead of relays, I suspect not. The automotive industry has a strong avoidance of using transistors or FETs to supply current to external loads they have no control over. Protection circuits against excessive loads are relatively complex and relays are bulletproof and cheap. The use of semiconductors to drive (say) injectors is a necessity, and also safe since no one is going to connect anything but an injector. But some fool is certain to short out a light (or the light may do it itself!). Also, the inrush current of lamps is death on semiconductors, unless they are grossly oversized to handle it. Further, relays dissipate no heat, but any semiconductor switch has intrisic resistance (in FETs the spec is its "Rds(on)"), and that resistance results in heat that needs to be dissipated.

 

As someone who designs high power switchmode DC-DC converters, the limitations of semiconductors is something I live wit every day. Relays, on the other hand can easily handle massive short term overloads.

Link to comment

Ever considered a career in politics?

 

In the interests of peer review, by which we can maintain quality standards for the information promulgated in these pages and minimise the birth of urban legends and just plain falsehoods.

 

Look at the second picture in this thread.

 

Now look up the reference printed on each of the two power components -- BTS432. Google finds it if your reference books only have thermionics.

 

Yup, it's a power FET with a pretty comprehensive range of protective functions on-chip.

 

Please stop guessing at what's going on, especially when others have already posted what really happens.

Link to comment
Ever considered a career in politics?

 

In the interests of peer review, by which we can maintain quality standards for the information promulgated in these pages and minimise the birth of urban legends and just plain falsehoods.

 

Well now, aren't we just a bit testy! There was nothing "urban legend" about what I said. There's no question that you are correct in this instance. But I was venturing an opinion based on the way the signal relay is designed in both my old K100 and both my mid '90s automobiles (yes, I take these things apart out of interest).

 

Please stop guessing at what's going on, especially when others have already posted what really happens.

Others did not post what "really happens". All that was posted was clear evidence to show a pair of MOSFETS were used instead of relays in this particular device. This is not central to the actual functioning of the device and cannot have any effect on the original reported problem.

Link to comment

As mentioned, your '04 RS uses a solid-state flashing unit. If it turns out to be the unit itself, consider replacing it with the Kisan signalMinder unit. Cheaper than the OEM one and adds several features. Auto-cancel and same button cancel for example.

Link to comment

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...