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Another dang rear brake pressure switch failure.

Started by FLFBRider, June 15, 2020, 04:08:08 PM

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FLFBRider

This is the 3rd time in 5000 miles. :emoGroan:

The last one I coated with high temp silicone to help isolate it from the engine heat and it still failed. My brake fluid is Lucas dot 4 and is not silicone based. I know some switches will not work with a silicone based fluid.

Bike is a 09' Fatboy. The switch is close to the engine case and takes on alot of heat. But since I coated it with the high temp silicone and spaced it out away from the case I figured it would last. NOT! It has stock head pipes and Rinehart slipons. I run a Jagg 6 row cooler and my oil temps are only at 205-210.

This time I installed an Excell made switch. I have read that this switch is superior to other types and holds up well. Has anyone here had this same problem and found a way to cure it? I always check my lights before I ride and luckily I have always found it before I left home.

Thanks.

Hossamania

After three switches in 5000 miles, I would just leave it and use the front brake to light it up.
I don't have any advice on the switch, I've not had one fail.
If the government gives you everything you want,
it can take away everything you have.

PoorUB

I doubt engine heat is killing it. How far away is the exhaust. Also I doubt covering it with RTV does any good. It might take longer to heat it up, but it will heat up just the same. Either heat from the exhaust or the silicone fluid is killing it. Add a heat shield to block some exhaust heat perhaps?

Seems to me the master cylinder sits right at the junction of the engine and transmission, behind the front exhaust pipe. I know that Harley had trouble frying switches on touring models around that time.  Have you used the current replacement part, or always aftermarket?
I am an adult?? When did that happen, and how do I make it stop?!

FLFBRider

This time when it failed the brake light was stuck on, so using the front brake only wouldn't be an option.

The Lucas fluid is non-silicone based Dot4 so that didn't kill it. The rear master cylinder is located forward of the exhaust and not really that close at all.

The first replacement was a Harley switch. The second was a Bosch switch from NAPA. This is the first Accel switch I'm trying. I'm just hoping this cures the problem.

Thanks for the comments. :up:

FLFBRider

Wanted to add: The switch is located at the engine/transmission connection. It sits just below this area atop the frame. Once again the master cylinder is forward of the exhaust.

PoorUB

Sorry, I missed the part whee you said the fluid was not silicone based. Are you certain the switches have been rated for the fluid?

This isn't a huge wide spread problem with Harley, so I would suspect something you are dong is killing them. Hundreds of miles in slow traffic baking the switch? Try a different fluid?
I am an adult?? When did that happen, and how do I make it stop?!

Hossamania

Quote from: FLFBRider on June 15, 2020, 07:35:35 PM
This time when it failed the brake light was stuck on, so using the front brake only wouldn't be an option.

You could disconnect it to get the light to go out, then your front switch would work. Not necessarily a permanent solution, but would get you by in a pinch if out and about. I have friends that would call it a permanent fix!
If the government gives you everything you want,
it can take away everything you have.

Norton Commando

I had the same problem on my 90 FLHS.  I could never get the rear brake pressure switches to last more than a thousand miles or so.  It tried a myriad of different switch brands and all failed prematurely.  I finally rigged up a mechanical switch that I bought from J&P, which cured the problem.

Jason
Remember, you can sleep in your car, but you can't drive your house.

FLFBRider

I'm gonna see how this new switch works out.
If it too fails in short order I'm going to look into the mechanical option.

I never thought of the option to just disconnect the rear switch and just go with the front brake lever. Good think'n!  :up: That would keep me going.   :bike:

les

If I recall, the reason those switches were going bad back then is because the edges of the hex were too sharp, thus picking up too much heat from the exhaust.  The recall I think was to install replacement switches that had a rounder edge.  I'm wondering if you grind off the edges a bit more if that might help (assuming it's heat that's causing the problem). 

fbn ent

You beat me to it. I remember having to replace a few with updates that were heat related but I didn't know what the issue was. I don't have the updated part number anymore.
'02 FLTRI - 103" / '84 FLH - 88"<br />Hinton, Alberta

Coyote

Harley changed switches due to them failing from heat from the cat. at one point.

chipthedonkey

The recall covered 2009-2012 bikes.

NHTSA CAMPAIGN ID Number: 11V506000

fbn ent

'02 FLTRI - 103" / '84 FLH - 88"<br />Hinton, Alberta

FLFBRider

The first replacement switch I used was a small diameter unit.
It's 2 3/4" inboard of the exhaust, I just measured.

The new Accel switch I just put on is a much larger diameter unit.
This is the new switch I just installed ACCEL (ACC 181101)