Indicators not working on Aprilia Falco

[A_morti]

That's the diode mod you've stumbled on. In the original circuit, current will flow across the bulb from either side and end up at earth through the other side indicator's earth. That's fine for incandescent bulbs as the dash bulb is much lower wattage but it won't work for LEDs and you get all 4 flashing together, so you have to put a pair of diodes in there and supply a separate earth.

I suspect that even if it's still working as intended (IE the scotch locks didn't fail) then it could be the problem, so try to undo all that. If it's been "upgraded" with an LED you'll also need to undo that and reinstall an incandescent bulb. If it's a small one under 5w, best to get the right one or it'll potentially melt the dashboard.

The flasher relay is looking less likely at this point, but it won't hurt to just bridge the two pins. Very easy to do, and eliminates it from enquiries.

[Mr Moofo]

Perhaps the indicators are fine and you just need to throw away the falco?

[iansoady]

The diode mod I know uses 2 diodes feeding the indicator bulb - one from each side - with the other side to earth. Not quite sure how a_morti's works.....

But agree disconnect all wiring to the warning light first.

[mangocrazy]

I'm reluctant to disconnect or bypass the diode plug, as from my reading of the lighting circuit diagram it has a function entirely unrelated to the indicators. I've attached a screenshot below from the workshop manual PDF that clearly shows the diode and its connection. And I'm pretty sure I've disconected the loopback/diode wiring and it made bugger all difference to the indicators.

Falco lighting circuits.JPG (176.11 KiB) Viewed 1810 times

There is a specific section in the manual for checking the LAP diode (see below), so I don't believe it has any relevance to the mafunctioning indicators, although I'm happy to be proved wrong.

Falco LAP diode checking.JPG (279.8 KiB) Viewed 1810 times

Next time I'm back I'll definitely investigate the dashboard indicator light and compare it to the specs for the OE indicator light (12V - 3W, according to the manual).

The bike would undoubtedly be worth more as individual parts than it would be complete, but I'm resisting that line of thinking for the time being...

[A_morti]

The diode mod I know uses 2 diodes feeding the indicator bulb - one from each side - with the other side to earth. Not quite sure how a_morti's works.....

But agree disconnect all wiring to the warning light first.

That's the mod I'm thinking of. If it's somehow got broken (they're always bodged together) or disconnected , then it could be robbing the indicators of their earth connection.

I've never heard of a LAP diode and in that diagram it doesn't seem to have anything to do with the indicators. It might be doing something quite different.

[mangocrazy]

The V60 Aprilias all had a lap timing facility as well as the ability to change between mph/kph, degrees C/F, set the rev limit warning light etc. etc., so I suspect that's what the diode arrangement is connected to. I've only found one Scotchlock on the whole of the wiring loom, and that was used to splice into the fuel injection circuit for the Power Commander (which I've removed).

While I haven't tested out the indicators individually, I'm leaning towards the view that the problem is down to the lack of an earthing point for the indicators. I'm also intrigued to know how a two-pin flasher relay works. Where does it derive its earth from?

[iansoady]

The two pin unit just earths through the indcator bulbs. Mist are a mickey mouse bimetallic strip arrangement which heats up as current flows to make / break thecontact.

[Ssray]

I'd test the indicators wired to the bulb socket first, my cbr600 was a fast flasher, new pattern indicators to replace led ones and 8 found high resistance in one wire that I then replaced.

[Big Red]

There are 2 types of 3 pin flasher relays.
It is down to the terminal positions which one you will need.
A wiring diagram will point out what wires connect to what terminal.

Sorry, just realized its a 2 pin

[Felix]

I changed all but the headlamps on my camper bus. Indicators were a pain in the arse but this was due to the bulb on the dash and being to lazy to strop and swap that over i bought a relay suited to LED and they work a treat. https://www.rg-racing.com/browsebike/Ap ... GRELAY001/

[mangocrazy]

Today I had to go back to Stafford to house-sit while the builders fitted a new toilet window, so I took the opportunity to revisit the Falco indicators and (more importantly) test all the indicator bulbs/housings. I ran Live and earth directly from the battery to the two indicator pins on the 2-way connectors. Both LH side indicators lit up when tested, but only the RH front. Investigation showed a furry bulb/socket. I replaced this with a spare, retested and all was well - all 4 indicators function when fed with 12V and Earth.

However when I try to get the things to flash when connected to the indicator circuit, they stubbornly refuse to do anything. No change there, then...

The horn hadn't worked either, and I was beginning to think there was a common fault. There wasn't. I fitted a new (remarkably loud) horn off ebay and it made me jump when I pressed the horn button (the volume, not an electric shock). So the only electrical issue left now are getting the goddam indicators to work.

It simply has to be an earthing issue, as far as I can see. My plan, admittedly sketchy, is to run fresh earths from the battery and frame to a suitable earth point connected to the indicator circuit. The main problem is trying to figure out where this might be. I think I might start by attacking the instrument cluster and checking for dodgy earths there. Perhaps the indicator dashboard light might have something to reveal...

[iansoady]

To eliminate earthing problems, run a dedicated earth wire from both indicators on the same side. But also use the voltmeter to check the live feed is getting an (intermittent) supply when the switch is pointing in that direction. If all else fails, just rewire the indicators which is an easy job.

[mangocrazy]

If all else fails, just rewire the indicators which is an easy job.

Easy? Really?

[mangocrazy]

As an update to this, I still haven't figured out why the indicators don't work. I've spliced in a secondary earth to the two rear indicator leads and run that back to the battery, and it still hasn't fixed the problem. I've spoken to the Oracle on all things Aprilia (Griff at AP Workshops) and he suggested that the instrument cluster might be having some effect, as there is only one dash bulb for both indicator sides (i.e. just the one bulb flashes irrespective of which side indicators are (or should be) flashing). So I removed the instrument cluster from the black Falco, fitted it to my red Falco and the indicators worked perfectly. So that exonerates the dashboard.

To be honest I'm pretty much at my wit's end (which admittedly isn't a great distance), and it's the only thing stopping me from putting the bike up for sale.

Does anyone know a good motorcycle electrician?

[mangocrazy]

I think I might have found an auto electrician, and his name is Claude... Herewith the transcript of a conversation I had with an AI bot:


Here are some common reasons motorcycle indicators stop working and how to fix them:
Check these first (easiest)

• Blown fuse — Find the fuse box (usually under the seat or side panel) and check the indicator fuse. Replace if blown.
• Burned out bulb — Remove the indicator lens and inspect the bulb. If the filament is broken or blackened, replace it.
• Dead battery — A weak battery can cause indicators to not flash or not work at all. Check voltage (should be ~12.6V at rest).

If one indicator works but not another

• Likely a single blown bulb or a bad ground connection on that specific unit.
• Check the wiring connector at the back of the non-working indicator for corrosion or a loose pin.

If indicators come on but don't flash

• The flasher relay is likely faulty. It's a small plug-in unit (often near the fuse box or behind the headlight). Replace it — they're cheap and easy to swap.
• On bikes with LED indicators fitted as aftermarket: LED bulbs draw less current, which can confuse an old-style relay. You need an LED-compatible flasher relay.

If nothing works at all

• Check the handlebar switch — the indicator switch can corrode or fail, especially on older bikes. Spray electrical contact cleaner into it and toggle rapidly.
• Trace the wiring back from the switch to the fuse box looking for any chafed, broken, or corroded wires.
• Check all earth/ground connections — a bad ground is a very common culprit on motorcycles.

Quick diagnostic tip

Turn on the ignition and activate the indicators. Use a multimeter or test light to check for voltage at the indicator bulb connectors. If you have voltage but no light → bad bulb or ground. If no voltage → follow the circuit back to find the break.

What make, model, and year is your bike? I can give more specific advice if you let me know.

Fuse has been checked and is OK. All (4) bulbs are OK, working and receiving 12v when switch activated. Battery is registering 12.8v at rest. Handlebar switch has been replaced with a known good item and fault persists. Indicator bulbs are standard incandescent items. Indicator relay has been replaced with known good item and fault persists. Bike is a 2000 Aprilia Falco SL1000.

Good systematic diagnosis — you've eliminated the most common culprits. Given everything you've checked, here's where to focus:
The fault is almost certainly a wiring/ground issue
You have 12V at the bulbs but they're not flashing (or not working at all) — with a known good relay and switch, the circuit is getting power but something is wrong with how it completes.
Most likely culprits for a 2000 Aprilia Falco:

1. Bad earth/ground — most probable The indicators on the Falco share a common earth point, often at the rear subframe or under the headlight. A single corroded or loose earth point will kill all four indicators even though you have 12V at the bulbs.
• Trace the black earth wire from the indicators back to the chassis ground point
• Clean it back to bare metal, reconnect firmly
• Try running a temporary jumper wire directly from an indicator earth terminal to the battery negative — if they suddenly work, you've found it

2. Indicator warning light in the dash The Falco's flasher relay circuit runs through the dashboard warning light. If the dash indicator bulb is blown or the dash connector is corroded, it can break the relay's trigger circuit and prevent flashing or operation entirely. Check the green indicator telltale bulb in the clocks.

3. Wiring loom condition The Falco is now 25 years old. The loom is known to suffer from:

• Cracked insulation where it passes through the frame
• Corroded bullet connectors (Aprilia used a lot of these in 2000)
• The connector block behind the headlight is a common trouble spot — unplug each connector, inspect for green corrosion, and apply contact cleaner

4. Ignition switch feed The indicator circuit on the Falco is fed via the ignition switch. Even though other things work, the specific terminal feeding the indicator circuit in the switch could be intermittent — worth checking voltage directly at the relay feed wire with ignition on.
Recommended next steps in order:

1. Run a temporary earth wire direct to battery negative on one indicator — rules out the ground immediately
2. Check the dash telltale bulb
3. Pull and inspect the headlight-area connector block
4. Get hold of the Falco wiring diagram (available on the Aprilia Falco owners forum / FalcoForum) and trace the earth path systematically with a multimeter set to continuity

The FalcoForum community is also very active and model-specific — someone there will almost certainly have seen this exact fault before.

I've run secondary earth wires from battery negative terminal spliced into the two rear indicator bulb cables, with no improvement. I've also replaced the dashboard/clock assembly with a known good item with no improvement. Thank you for your helpful suggestions.

Good work — you're methodically eliminating everything. Let's re-think this logically.
What we now know for certain

• 12V is reaching all four bulb connectors when switch is activated
• Earth is confirmed good (you've bypassed it)
• Relay is good
• Switch is good
• Dash is good
• Bulbs are good

The critical question is: what exactly is the fault?
Can you clarify what the indicators are actually doing?

• Do they illuminate but not flash (stay on solid)?
• Do they not illuminate at all despite 12V at the connector?
• Do they flash but incorrectly (too fast, too slow, erratically)?
• Do they work intermittently?

This matters a lot because:
If they illuminate but don't flash: With a known good relay, this points to the relay not receiving a proper switched earth to trigger the flash cycle. On the Falco the relay earth path is separate from the bulb earth. You may have earthed the bulbs but not the relay body/earth pin itself. Check which pin on the relay is the earth and run a direct wire from that specific pin to battery negative.

If they don't illuminate at all despite 12V present: This is electrically strange — 12V at the bulb connector with good bulbs and good earth should produce light. Double-check your voltage measurement was taken between the live feed wire and a known good earth (not chassis), and that 12V is present with the switch held on, not just momentarily.

If they flash incorrectly: Could point to a resistance issue somewhere in the loom causing the relay to cycle erratically.
What are the indicators actually doing when activated?

They do not illuminate at all. I measured 12v on all the positive leads to the indicators and also established continuity between the earth cables and battery. I'm beginning to doubt my own sanity...

Don't doubt your sanity — this is a genuinely puzzling fault, but there's a logical explanation. Let's think about this very carefully.
Something doesn't add up electrically
You have:

• 12V on the positive feed ✓
• Continuity to earth ✓
• Known good bulbs ✓

Bulbs should be lighting up. The fact they aren't means one of the following:

Most likely explanation; voltage present but not switched

There's a critical difference between:

• Switched 12V — voltage that appears when the relay completes the circuit to allow current to flow
• Phantom/ghost voltage — a small voltage that appears on a multimeter in an incomplete circuit due to induction from adjacent wires in the loom, but cannot actually drive current through a load

Test this immediately: Connect a 12V test bulb (not a multimeter) directly between the positive indicator feed wire and earth. A multimeter will show phantom voltage. A test bulb will only light if real current can flow. If the test bulb doesn't light, you don't actually have a live feed — you have induced voltage.

2nd possibility; circuit is open between relay and bulbs

Even though you have 12V at the bulbs, trace where that 12V is coming from:

• Is it genuinely from the relay output?
• Or could there be a break in the loom with voltage back-feeding from another circuit through a shared connection?

3rd possibility — wrong relay pinout

Even with a known good relay, if it's wired into the Falco's socket and the pinout doesn't match exactly, it could be passing voltage through in a way that reads on a meter but doesn't complete a working circuit.

• What is the relay part number you're using?
• The Falco uses a specific 3 or 4 pin relay — confirm the pinout matches exactly

The test bulb check will likely crack this immediately. What do you find?

That's very interesting. I am not able to run any checks at the moment, as I am geographically distant from the bike. I will print out this dialogue and will follow your recommendations when I next have physical access to the bike. Thank you again.

You're very welcome — it's been a good systematic diagnostic session and you've done excellent work ruling things out methodically.
The phantom voltage test with a test bulb is almost certainly going to be the breakthrough when you get back to the bike. It's a surprisingly common trap that catches even experienced mechanics — a multimeter is too sensitive and will show voltage that simply can't drive a real load.
When you do get back to it, work through in this order:

1. Test bulb on the indicator feed wires — confirms whether you have real current or ghost voltage
2. Check relay pinout against the Falco wiring diagram if the feed is genuine
3. FalcoForum — worth posting there too as someone will likely have seen this exact combination of symptoms

Good luck with it — feel free to come back and update, or if you want to work through the next steps once you're back with the bike. It'll be satisfying to crack it after such thorough diagnosis!

Thank you again. I will report back with findings.

[iansoady]

That's interesting. The "ghost" voltage mentioned can happen with LEDs that pass a small current - enough to show on a multileter but not enough current to power anything. The process described is very similar to what I and others have said in this thread.....

[mangocrazy]

I'd never considered ghost voltages, and always assumed that what a multimeter reported was 100% reliable. But it's not presenting a load, so isn't necessarily accurate. Every day's a school day...

[cvilla]

Mango, you can't leave us hanging like the end of 'stenders;)
It's a BH weekend, can you just nip down your garage and get testing....
I recall your garage/bike may be someway away and there a fuel issue, but how is Claudie going to sleep!!

Please; Next episode we need to see pics of the lightbulb working ! Thanks C.

[iansoady]

Claude never sleeps. And he(!) tells me he always forgets the conversations......

[mangocrazy]

Mango, you can't leave us hanging like the end of 'stenders;)
It's a BH weekend, can you just nip down your garage and get testing....
I recall your garage/bike may be someway away and there a fuel issue, but how is Claudie going to sleep!!

Please; Next episode we need to see pics of the lightbulb working ! Thanks C.

The garage is over 70 miles away, but I will be returning there in midweek (but for different reasons) so I may have a chance to do some testing. I will need to rig up a test light, but I can give that some thought in the interim.

Is it possible to come back to a chat with Claude and continue where you left off? I know Claude says he doesn't remember any conversations, but...