[elocklear]

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I have a 2005 GL1800. For no known reason, the brake lights will not turn off. Took the bike to a local dealer today and they cannot figure out why the brake lights are staying on. To save in more diagnostic fees they are suggesting I let them replace the entire rear wiring harness.

Has anyone experienced this?

 

[DaveO430]

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It's probably as simple as a stuck or misadjusted brake light switch. But have you done anything to it like replacing a bulb?

 

[derekhendry]

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After market chrome cluth and brake levers can sometimes get stuck and not go forward enough, simple test is to turn the bike on and push the front brake lever foward away from the grip. The other thing it might be is a stuck relay, would not think it was the wiring harness. A good dealer would be able to fault find without starting to guess and swap things

 

[AZgl1800]

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I vote for a switch that is being operated as mentioned.

Very doubtful it is a wiring harness issue. Especially in a bike that is so young.

 

[Broke Winger]

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Unless the dealer is gonna do it for free tell him to stop trying to rip you off!

There is absolutely nothing in the wirign that would make the brake lght stay on. A short would make it not come on at all. But the only thing that wwould make it stay on is a stuck switch or stuck relay.

 

[globetrotter]

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If you have done nothing with the rear lights, I would be looking at the two brake light switches, one on the front brake, especially if you have recently fitted chrome levers, and the other on the foot brake.

 

[Daveo]

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I had the exact same problem on my 2008 1800. It was the relay located under the seat. Honda replaced it under warranty in about 30 minutes.

My relay failed in temperatures over 100, if it was 98 everything worked fine. I first noticed it when I was riding in 102 weather. My first clue of a problem, the cruise control wouldn't work.

Hope this helps

Daveo

 

[Kit Carson]

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If I had to guess I would head for the relay. It is under the seat in the relay box, it is the one that is located third row down and third one over.

Kit

 

[Wolfman]

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I had it happen twice on my 1200 and once on my 1500.

All three times it was the brake light switch on the rear brake pedal.

I can't speak for the 1800, but on the 12 and 1500 it is a very inexpensive part and very easy do-it-yourself replacement.

Also in all three cases, I was able to verify before buying the replacement switch by playing with the old one by hand. Follow the spring up from the brake pedal to locate the plunger that the spring pulls on. Jiggle the plunger in and out, and side to side and see if the brake light goes on/off.

On all of mine, when I pressed on the brake pedal, the light came on. When I released the light stayed on. But when I pushed the plunger the light went out. It was as if there was some corrosion inside the switch and the switch could not return home under it's own strength.

If that doesn't happen for you, and therefore doesn't answer your question, you should be able to unplug the rear switch and see what happens. On the 1200 and 1500 the switch wiring was only about 12" inches long and easily followed to where it plugged in. Hopefully for you the 1800 is the same.

I do not know this, but I would guess that the brake light switch is normally open and depressing the brake pedal closes it. If this is true, unplugging the switch should give you an open condition and the light should go out. One of the guru's should be able to confirm if this is true or not.

But if I was a betting man, I would put money on that rear brake switch being at fault.

 

[William_86]

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i would also check the switches. i cant believe honda dealers wanted to sell you the rear harness without even first checking the switches or relay. thats why they call them stealers.

 

[DaveO430]

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I have looked in the manual I downloaded and can't find anything on switch adjustment so there may not be any. If you slowly press the front brake lever,engine off and in a quiet place you should hear 2 clicks, same with the rear pedal. One click is the cruise cancel switch, the other is the light switch. If you don't hear 2 clicks one of the switches is probably stuck on. If not that it may be the relay but a stuck closed relay is pretty rare. Normally they fail open, either bad contacts or bad relay coil.

 

[treker8098]

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I would agree with verifying the switches, but my GW has some aftermarket lights located just above the exhaust that are attached with one fastener. One of the lights had rotated down so that the metal casing touched the exhaust causing all the brake lights to come on.

 

[Daveo]

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The 1800 has micro switches not the older plunger spring arrangement. They are not adjustable according to the shop manual (2008 at least).

 

[Kit Carson]

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The brake switches are easy enough to check, do not have to remove anything but the right side cover for the rear. Just stick a needle through one of the wires from the switch, using a tester simply read if there is voltage from the wire back to ground.
If so it is a bad switch. If not head for the relay.