LED indicators are an easy visual upgrade on the BMW R1100S. They are brighter, react faster and draw very little current. The problem is that the original BMW flasher module was designed around incandescent indicator bulbs. Once the current draw drops sharply, the module interprets it as a failed bulb and responds with rapid flashing.
The usual solution is an aftermarket LED relay or load resistors. Both work, but neither is ideal.
Load resistors waste the electrical advantage of LEDs by turning power into heat. Many replacement relays correct the flash rate, but they do not retain the R1100S’ original automatic turn-signal cancellation. Several aftermarket R1100S LED relays state this explicitly: they are LED-compatible, but have no automatic cancellation function.
There is a better option: modify the original BMW relay.
This is not a new internet myth. The modification has been documented for years across BMW Oilhead communities, including R1100S, R1100GS, R1100RS and R1150 variants. The principle is simple: the original relay’s bulb-load monitoring circuit is bypassed or disabled, while the relay’s timing and control logic remain in place. The result is a normal flash rate with LED indicators, while retaining the factory self-cancelling function.
The important caveat is that BMW used several different relay revisions. The modification is valid, but the exact work depends on the relay fitted to your bike.
Why LEDs Cause Fast Flashing
The original incandescent indicators draw substantially more current than LEDs. The BMW relay monitors that load. If the load is lower than expected, it assumes a bulb has failed and switches to rapid flashing as a warning.
With LED indicators, nothing is necessarily wrong. The relay is simply seeing too little current.
The relay modification removes that current-sensing behaviour. A documented version of the modification changes the unit so that it flashes at roughly one cycle per second regardless of bulb load.
That means it will work with LEDs, conventional bulbs, or a mixture of both.
Why Not Just Fit an LED Relay?
You can. There are plug-in LED-compatible relays sold specifically for the R1100S, and they will maintain a normal flash rate across a wide power range.
But most do not preserve BMW’s original auto-cancel function. Boxertrix owners have specifically confirmed that one common LED relay eliminates automatic cancellation, even though it solves the rapid-flash issue.
That matters more than people think. The R1100S system will normally cancel the indicators automatically after a short period, depending on time and riding conditions. Owners often do not even realise the function is working until they deliberately test it.
For a clean OEM-style conversion, keeping the original relay is the better route.
The Relay Versions Matter
Do not open your relay and blindly follow a photograph from another bike.
BMW used several different flasher relay layouts across the Oilhead range. They may look broadly similar externally but have different printed circuit boards internally.
The three versions most commonly discussed are:
| Relay part number | Known modification |
|---|---|
| 61 31 2 305 700 | Cut-track style modification |
| 61 31 2 306 979 | Cut-track style modification |
| 61 31 2 306 101 | Bridge/jumper style modification |
A UKGSER discussion identifies the 61 31 2 306 979 relay as the common cut-track version. It also notes that a 61 31 2 305 700 relay taken from a 1999 R1100S used the same PCB layout and was expected to accept the same modification.
The earlier 61 31 2 306 101 version uses a different board layout and has been documented as requiring a jumper between two points rather than cutting the same trace.
So the rule is simple:
Identify the relay by its actual PCB and part number, not by model year alone.
The Two Known Modifications
1. Cut-track relay version
This is the most common version seen in later Oilhead applications and in many R1100S relays.
The modification consists of interrupting the PCB trace that carries the lamp-load sensing signal into the control circuitry. Once that circuit is interrupted, the module no longer reacts to the low current draw of LEDs as if a bulb has failed.
The photos supplied here show this style of relay modification. The marked areas identify the relevant printed-circuit tracks. Depending on the board revision, the modification may involve one trace or two closely related sections of the sensing circuit.
The key point is not the number of cuts. It is that the load-sensing path is interrupted without damaging the rest of the relay logic.
Pelican Parts users documented this approach specifically for fast-flashing R1100S indicators and reported that cutting the relevant PCB trace makes the relay flash at a normal fixed rate regardless of load.
2. Bridge/jumper relay version
The older relay layout is different.
Rather than cutting the same sensing track, the modification is made by soldering a small jumper wire between two marked points on the PCB. This bypasses the part of the circuit that expects the higher current draw of incandescent bulbs.
The supplied photo with the yellow marking shows this version clearly: two points are linked with a short wire bridge.
A forum discussion covering the 61 31 2 306 101 relay confirms that this revision uses the bridge method, while the later 61 31 2 306 979 version uses the cut-track method.
What the Modification Preserves
When done on the correct relay version, the original BMW module remains in the bike. That means it should continue to provide:
- normal indicator flash rate with LED indicators;
- hazard-warning operation;
- dashboard indicator function;
- original relay integration with the BMW switchgear;
- automatic cancellation.
That is the major advantage over a generic aftermarket relay.
There is one separate function worth noting: some BMW relay revisions allow cancellation by pressing both left and right indicator buttons together. Not every relay revision supports that feature. Owners have reported that the 61 31 2 305 700 unit can work normally but may not respond to the two-button cancellation shortcut.
That is not the same as losing the normal automatic cancellation function.
Before You Start
This is not difficult electronics work, but it is small-scale and easy to get wrong.
You need:
- a fine-tip soldering iron for the jumper version;
- a sharp craft knife, PCB cutter or Dremel with extreme restraint for the cut-track version;
- a multimeter with continuity function;
- magnification;
- a camera or phone to document the original board;
- heat-resistant work surface;
- patience.
Do not use a large soldering iron. Do not scrape around blindly. Do not cut tracks based only on a similar-looking relay found online.
Ideally, buy a cheap spare relay and modify that first. Original BMW relays are no longer cheap enough to treat casually.
Step-by-Step: Safe Method
1. Remove the relay
Disconnect the battery negative terminal first.
Remove the original flasher relay from the motorcycle and photograph the part number and connector orientation before opening it.
2. Open the relay housing carefully
The relay case is usually clipped or lightly sealed. Work around the edge gently with a thin blade. Avoid levering against the PCB or connector pins.
3. Identify the PCB layout
Compare your board against the photographs in this guide.
There are at least two relevant layouts:
- cut-track layout;
- bridge/jumper layout.
If your board does not clearly match either layout, stop. Do not improvise.
4. Make the modification
For the cut-track version:
- cut only the marked copper trace or traces;
- make the cut narrow and clean;
- use a multimeter to confirm there is no continuity across the interrupted track;
- make sure no adjacent tracks were damaged.
For the bridge version:
- pre-tin a very small piece of insulated wire;
- solder it only between the two marked pads;
- inspect carefully for solder bridges to nearby tracks;
- confirm continuity through the new bridge with a multimeter.
5. Bench-check before sealing
Before closing the relay housing permanently, reinstall it and test:
- left indicators;
- right indicators;
- hazard lights;
- dashboard indicator;
- normal flash rate;
- automatic cancellation after a short ride.
Only reseal the housing once everything works correctly.
6. Seal the relay properly
Use a small amount of non-corrosive RTV silicone or a suitable electronics-safe sealant if the original housing no longer clips tightly.
Do not fill the housing with sealant. It must remain serviceable.
What You Lose
The modification disables the relay’s original low-load or bulb-failure detection behaviour.
That means the bike will no longer warn you of a failed indicator bulb by rapidly flashing.
For an LED-equipped R1100S, that is usually an acceptable trade-off. But it means routine checks matter more. Verify all four indicators before riding, particularly after maintenance or washing the bike.
What Can Go Wrong
The main risks are straightforward:
- cutting the wrong PCB trace;
- damaging adjacent copper traces;
- overheating a component during soldering;
- creating a solder bridge;
- fitting the relay back incorrectly;
- assuming every R1100S uses the same relay layout;
- blaming the relay when the actual problem is poor LED wiring, bad earths or low battery voltage.
The relay is solid-state, and forum reports show that shorts or overloads can damage its output components. That is another reason not to use poor-quality LED indicators or improvised wiring.
Verdict
The LED relay hack is legitimate, well established and more elegant than adding hot load resistors or fitting a generic relay that deletes BMW’s original self-cancelling feature.
The core principle is proven:
- LED indicators reduce current draw;
- the original relay responds with rapid flashing;
- bypassing the load-sensing circuit restores normal flash rate;
- the rest of the original relay logic remains in place.
But there is no single universal cut location.
BMW used multiple relay revisions, and the relay must be modified according to its PCB layout. The R1100S can use a cut-track version such as 61 31 2 305 700 or 61 31 2 306 979, while older-style relays such as 61 31 2 306 101 may require a soldered jumper instead.
That is the whole job: identify first, modify second, test before sealing.
Safety note: This is an owner modification to a safety-related lighting circuit. Perform it only if you are confident working on small electronic assemblies. Test every function before using the motorcycle on public roads.