Indicators flash too fast

The indicators blink much faster than normal, on one side or both. Most bulb-type flasher relays measure the current through the lamps. If the current is too low, they flash fast on purpose, to warn you that a bulb has failed. So fast flashing usually means one lamp on that side is not drawing its normal current: a blown bulb, a poor earth, a lower-wattage bulb, or an LED indicator.

Is it safe to ride?

Yes, with care. Check that every indicator still lights, because one may be out. Riders behind you may not see a dark lamp.

Quick checks first

• Fast on one side only, or on both sides?
• Walk round the bike with the indicators on. Is one lamp dark or dim?
• Have LED indicators, or bulbs of a different wattage, been fitted?
• Fast only at higher revs? The supply voltage may be high: see step 5.

Diagnose it step by step

1Is one lamp on the fast side dark or dim?

• Dark: Replace a bulb. K-Light 125 indicator bulb: R10W (PDF p. 99). Use the same wattage as the other indicators.
• Dim: go to step 3.
• All lamps light normally: go to step 2.

2Are any indicators LED, or are bulbs of a lower wattage fitted?

• Yes: this is the cause. LEDs draw far less current than bulbs, so a bulb-type flasher flashes fast. Kellermann, an indicator maker, notes that flash rate may rise after new indicators are fitted (see sources). Fix it properly with Fit LED indicators correctly: fit an LED-type or load-independent flasher, or a load resistor per LED lamp.
• No: go to step 3.

3. Does a dim or flashing lamp have a poor earth? Indicators that earth through their stalk or mounting bolt often rust there. Set the multimeter to DC volts (V with a straight line). Indicators on. Red probe on battery positive, black probe on the lamp's earth wire or metal body. The reading should pulse to close to battery voltage.

• Low or nothing: clean the earth: Clean and tighten earth connections.
• Good: go to step 4.

4. Is the bulb holder or plug corroded? Look for green powder, a loose bulb or a pushed-back pin.

• Yes: Clean and seal electrical connectors.
• No: go to step 5.

5. Is the flasher itself faulty? Fast on both sides with all lamps correct often means a failing flasher. Test it with Test the indicator flasher relay, or swap in a known good flasher of the correct type.

• Normal with a new flasher: the old one was faulty.
• Still fast only at high revs: check the charging voltage is not too high, see Battery overcharges and bulbs blow.

6. CAN-bus bike? On bikes where the dashboard or a control unit flashes the indicators, fast flashing or a lamp warning can come from a non-approved LED, a poor earth or a bad holder. HELLA notes that a faulty earth can be reported as a bulb fault. Check those first, then see a dealer.

Causes, most likely first

Reference values (K-Light 125)