Unstable brake light problem

Recently changed my taillight to a motodynamic model and did all the connection using the provided connectors. No messing with the original harness and soldering involved (except for the turn signal). Finish the job with some dielectric compound around the connections to protect them from water.

The tail light has a flashing stop so when I brake it will flash 3 times before going steady. However I noticed that when the bike is cold, braking would initiate the 3 consecutive flash then go steady for a couple of seconds before doing the flashing again and it would repeat itself. Front or rear brake makes no difference. Delay between flashing varies. The weird part is that after a good warm up / some 10 mins of riding this behaviour will stop.

Additionally and I am not sure it is related but it appeared at the same time - the radiator fan seems to be acting up. It usually kicks in at around 100deg and stays on until it goes back to around 96 deg. But a couple of times, it would start then stop while it is still at 100 deg or higher and picks up again after a few seconds. And today it didn't start until it was at 112 deg and thought the fuse must have blown. However when I stopped the bike, I heard the fan starts blowing.

Otherwise every other electrical component is working fine.

I intend to have a look the wires I touched while doing the tail light and do some cleaning on the connectors. I do not have a volt meter to test and I don't think it is the brake switches since both front and rear are having the same behaviour. Any suggestion on specific parts I need to verify? Could avoid me going through everything trying to find the culprit.

Sounds like the added on unit is faulty, unless you have a real crappy connection that's expanding/contracting with heat.

If you want to disconnect the light fixture and hook it up directly to a battery (by passing the bikes electrical system), this would verify the above..

Just a suggestion, as the FZ has ONLY ONE TAIL LIGHT, I opted to put a second Hyperlight combo running /flashing brake light on the rear. Should the stocker burn out, I still have the LED working (basically insurance I have a tail light). The Hyperlight is just above the tag and is approx 2-3 x brighter (in running mode than the stocker) and extremly noticable when flashing. I did have a module quite working after 5-6 years (acting like yours), they replaced the module without question, receipt, etc, EXCELLENT customer service.

Hyperlites Flashing led motorcycle brake lights, runing lights, and turn signals, Standard Dual Function


As for the fan, obviously, make sure there's nothing inbetween the fan and radiator hanging it up. IF you did replace the smaller fuse for the fan (as discussed on the forum), I'd put the 20 back in just to see if the issues change.

If you haven't done a coolant change within two or three years, I'd be doing that. If the sensors are getting "gooed up" that's not helping and fresh coolant would help the system work at 100%.

Another member, suggusted for coolant changes, to save a potential headache, to just remove the lower water pump hose to drain the system vs the small (and sometimes fragil drain plug). I'd also pull and clean the radiator cap and make sure thats nice and clean.

The fan seems to have gotten worst. It did not start at all today even at 117 deg celcius!

Yes I did change the fan fuse for a 10amp and have put the 20amps back but still nothing. The 10amp did not burn and the fan can rotate freely. I went back to check the cables for the tail light in case it is related but it seems just fine.

The coolant was changed last summer but will add more coolant in case there isn't enough. But if the thermostat is showing the right temperature then the coolant just be ok, no?

I am more worried about the fan now than the tail light and I am currently clueless about what to do It seems something is loose somewhere but where?

You can run two wires to the fan itself after disconnecting it and hook it up directly to a battery to check it. Try starting the fan in different spots in case there's a "dead spot" in the armature.

If your riding at say 50 MPH, the temps should stay fairly steady and of course warm up when stopped. If that is happening, the thermostat should be fine (seems to be opening fully).

There is a Thermosensor switch at the rear of the engine cylinders (closer to the right side) but its rare that fails.

The relay for the fan should be under the left pod (should be the second one back, from the front, in a rubber boot), about in the middle. If its failing, you'll get an intermediate connection/power (sometimes it works, sometimes it doesn't).

I'd check the fan first, then the relay (I believe its a standard relay). The relay to the right of it it the "dimmer" relay (this is all per my Yamaha PDF manual). If they have the same part #, you can likely swap them and try the bike.

**Also, just to cover the BASIC'S, please pull the radiator cap and clean it with fresh water, maybe an old toothbrush too. If its not sealing fully, it'll cause issues... Make note of the locking assembly before you remove it..

Thanks for guiding me with this and this reminded me of a thread to troubleshoot the radiator fan:
http://www.600riders.com/forum/garage-mechanical-help/42274-radiator-fan-problem-diagnosis.html

So I have short-circuited the relay but it wouldn't start anyway. I have not reached the fan connector to connect it directly to the battery because it is not easy to reach and I need to go a friend's place to work as i don't have much space in the parking at my condo building.

So far I think the problem is more complex than the tail light or just the fan. This is what I have seen so far:

- Fan turning on is random. Bike is on its side stand engine running or not and it would turn on at some point (when it should have a long time ago).
- The fan staying off when it shouldn't is getting more and more frequent with time.
- Turn off engine and holding the brake lever, the tail light gets steady current.
- Turn on engine and holding the brake lever, the tail light gets unsteady current. Flashes every 2-3 seconds. More frequent as I rev the engine.
- With engine on, the turn signals frequency also seems to be affected. Most probably getting unsteady current. I have an electronic relay.
- The problem is apparent because of the Motodynamic tail light has 3 quick flash everytime the current is cut even if for a fraction of a second. I probably wouldn't have noticed with a regular tail light.
- The tail light was tested separately and works perfectly.
- All fuses are good.
- Looked for broken connectors cables at the relays and fuses but everything seems to be good as well.
- I haven't noticed anything unusual with the engine, nor the position light/plate light/ or hid headlight. The other lights could be affected by the problem but just not visible given the current seems to cut off for a fraction of a second.

You sure its completely full of coolent? That will change the behavior of the fan cycles.

The tail just sounds like a bad connection. Anything close to the exhaust or being subject to heat? Specifically wires not routed in OEM locations/or with aftermarket exhaust.

I found the problem! All that after changing the coolant and a few days of head scratching. I simply had to tug on this guy and zap the fan went off.

View attachment 48679

Good news is that I probably won't have to replace anything expensive. Bad news is that I have to remove a load of stuff just to get to the problem. There must be something loose inside and the brake light is also steady when the fan is working. It will also need a lot of cleaning as you can see in the pic.

Now I just need to find somewhere to do this work as my current working condition is just terrible.
View attachment 48680

elus1ve said:

I found the problem! All that after changing the coolant and a few days of head scratching. I simply had to tug on this guy and zap the fan went off.

View attachment 48679

Good news is that I probably won't have to replace anything expensive. Bad news is that I have to remove a load of stuff just to get to the problem. There must be something loose inside and the brake light is also steady when the fan is working. It will also need a lot of cleaning as you can see in the pic.

Now I just need to find somewhere to do this work as my current working condition is just terrible.
View attachment 48680

Click to expand...

Its hard to tell from the picture, is the wire for thre fan mis-routed/pinched?

The fan cable isn't pinched and doesn't seem misrouted either. The faulty connection comes from inside the frame. The cable looks funny in the picture because I've been gently pulling on it. It could be a bad connection along the fan cable or another cable close to it. I have an feeling that when the bad connection is fixed, the tail light will also work properly.

I just looked at my 07 fan wire. Its literally attached to the engine side of the fan, then runs up by the large AIR system hoses. Its is NOT VISABLE AT ALL from the front, period.

It appears to me someone had it apart and re-assembled it incorrectly. If you need pic's of mine, let me know and I'll shoot one. My moneys on pinched wires there

elus1ve said:

Recently changed my taillight to a motodynamic model and did all the connection using the provided connectors. No messing with the original harness and soldering involved (except for the turn signal). Finish the job with some dielectric compound around the connections to protect them from water.

The tail light has a flashing stop so when I brake it will flash 3 times before going steady. However I noticed that when the bike is cold, braking would initiate the 3 consecutive flash then go steady for a couple of seconds before doing the flashing again and it would repeat itself. Front or rear brake makes no difference. Delay between flashing varies. The weird part is that after a good warm up / some 10 mins of riding this behaviour will stop.

Additionally and I am not sure it is related but it appeared at the same time - the radiator fan seems to be acting up. It usually kicks in at around 100deg and stays on until it goes back to around 96 deg. But a couple of times, it would start then stop while it is still at 100 deg or higher and picks up again after a few seconds. And today it didn't start until it was at 112 deg and thought the fuse must have blown. However when I stopped the bike, I heard the fan starts blowing.

Otherwise every other electrical component is working fine.

I intend to have a look the wires I touched while doing the tail light and do some cleaning on the connectors. I do not have a volt meter to test and I don't think it is the brake switches since both front and rear are having the same behaviour. Any suggestion on specific parts I need to verify? Could avoid me going through everything trying to find the culprit.

Click to expand...

I had the same problem with my tail light. I contacted motodynamic and they said they've seen the problem before. They sent me (for free) a capacitor to splice into the brake light. Solved the problem and literally a 2 minute install.


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I figured a capacitor would easily solve the problem but I think it's not addressing the root cause but merely the symptoms. I wasn't having this problem before and it started pretty much at the same time my radiator fan started acting up. I'm thinking I've loose connection somewhere.

Besides, the capacitor will not resolve the turn signal blinking unsteadily.

elus1ve said:

I figured a capacitor would easily solve the problem but I think it's not addressing the root cause but merely the symptoms. I wasn't having this problem before and it started pretty much at the same time my radiator fan started acting up. I'm thinking I've loose connection somewhere.

Besides, the capacitor will not resolve the turn signal blinking unsteadily.

Click to expand...

I didn't read your whole post, I assumed the tail light always behaved like that. My apologies.


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zackattack784 said:

I had the same problem with my tail light. I contacted motodynamic and they said they've seen the problem before. They sent me (for free) a capacitor to splice into the brake light. Solved the problem and literally a 2 minute install.


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Click to expand...

elus1ve said:

I figured a capacitor would easily solve the problem but I think it's not addressing the root cause but merely the symptoms. I wasn't having this problem before and it started pretty much at the same time my radiator fan started acting up. I'm thinking I've loose connection somewhere.

Besides, the capacitor will not resolve the turn signal blinking unsteadily.

Click to expand...

Probably a diode and not a capacitor?

Motogiro said:

Probably a diode and not a capacitor?

Click to expand...

Motodyanimc told me it was a capacitor. They said the voltage from the bike wasn't stable enough when the brake was applied. This fluctuating voltage was dropping below the threshold for the stop alert function to activate which would cause the stop alert to activate multiple times even though the brakes were held down the entire time.

Whether this is true or not, I don't know, but whatever they sent me worked .


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You might be right actually, the capacitor could be the solution.

I took apart the air box and battery to look for the bad connections and found that the pin for the radiator fan was loose and had to fix it. Epoxied the pin so that it wouldn't slip back again. This means that my fan issue was isolated.

The unsteady tail light is still present and only appears when the engine is running and mostly when it is still cold. Could be that when cold, the current is less stable and is indeed going below the threshold and the tail light would initiate the flashing lights. Strange that it didn't do this before. There is always the possibility that I didn't notice it before either.

So they gave you a capacitor for your brake light, how about the turn signals? The tail light turn signal would re initiate the sequence in the middle of the running sequence as if it also lost the signal and had to start over. Did they give you a capacity for the turn signal as well?

Doesn't seem very clean imho.

zackattack784 said:

Motodyanimc told me it was a capacitor. They said the voltage from the bike wasn't stable enough when the brake was applied. This fluctuating voltage was dropping below the threshold for the stop alert function to activate which would cause the stop alert to activate multiple times even though the brakes were held down the entire time.

Whether this is true or not, I don't know, but whatever they sent me worked .


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Click to expand...

elus1ve said:

You might be right actually, the capacitor could be the solution.

I took apart the air box and battery to look for the bad connections and found that the pin for the radiator fan was loose and had to fix it. Epoxied the pin so that it wouldn't slip back again. This means that my fan issue was isolated.

The unsteady tail light is still present and only appears when the engine is running and mostly when it is still cold. Could be that when cold, the current is less stable and is indeed going below the threshold and the tail light would initiate the flashing lights. Strange that it didn't do this before. There is always the possibility that I didn't notice it before either.

So they gave you a capacitor for your brake light, how about the turn signals? The tail light turn signal would re initiate the sequence in the middle of the running sequence as if it also lost the signal and had to start over. Did they give you a capacity for the turn signal as well?

Doesn't seem very clean imho.

Click to expand...

I had no issues with the turn signals so sorry, no help there. I noticed my issue was rpm dependent, and like you, also occurred on a cold engine. After trial and error I discovered it was because of the fast idle when you first start the bike. Try this out. With the bike warm and idling normally, rev the engine and apply the brakes. You should get the same behavior you get on the cold engine. If you do, it's the same problem I had. You probably didn't notice it, it took me weeks to discover it.


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Just to add, I spliced my tail light turn signals into my existing turn signals and did not use the resistors built into the motodynamic sub harness. So we have ours wired differently.


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TownsendsFJR1300 said:

I just looked at my 07 fan wire. Its literally attached to the engine side of the fan, then runs up by the large AIR system hoses. Its is NOT VISABLE AT ALL from the front, period.

It appears to me someone had it apart and re-assembled it incorrectly. If you need pic's of mine, let me know and I'll shoot one. My moneys on pinched wires there

Click to expand...

I missed that post. Thanks for the offer but I have an explanation for the wiring route being different. This fan actually came from an dead Kawa. I got it for cheap last summer as the my fan had died from a rock stuck inside. The motor fits and all but the cable was shorter than the stock one so I had to take a more direct route. I also had to switch the connector pins from the Kawa to the Fz6 connector as it didn't match. One of the pin did not hold properly and with time it slid out and caused the issue. The pin isn't a perfect match either and it wouldn't hold securely inside the connector, so now it was epoxy on the back to secure them. All this jumping through loops to avoid buying a new fan.

The symptoms match perfectly. Engine off-no problem. Engine on and cold-flashing unnecessarily. Engine warm and revving - also flashing unnecessarily.

As for the turn signal, I am also not using the harness provided by Motodynamic. They are wired to my current turn signals and I have an electronic relay installed. It is not as noticeable as the brake light flashing, but it has the same behaviour nevertheless.

That bit comes from their website:

Q7: I noticed the Stop Alert for the brakes is activating on it's own while the engine is running and I am not engaging the brake lever. When the engine is off it does not happen. What could be wrong?

A7: This problem is common with older motorcycles or motorcycles with a lot of usage on the brakes. The hand or foot brake switch is the culprit and engine vibration is causing the contact points to go on and off triggering the brakes randomly. You can verify this by pulling out the brake fuse and see if the problem stops.

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zackattack784 said:

I had no issues with the turn signals so sorry, no help there. I noticed my issue was rpm dependent, and like you, also occurred on a cold engine. After trial and error I discovered it was because of the fast idle when you first start the bike. Try this out. With the bike warm and idling normally, rev the engine and apply the brakes. You should get the same behavior you get on the cold engine. If you do, it's the same problem I had. You probably didn't notice it, it took me weeks to discover it.


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Click to expand...