Brake light switch

[jgreg53]

I managed to get my mechanical brake light switch attached. Had to run a separate wire for the middle brake light.  Everything is working.

[kencombs]

My Ford Exp.edition was totaled because of that.  The worst thing is that the fire always starts almost directly under the master cylinder.  So the plastic reservoir melts  and ads brake fluid to the fire.  I put mine out with an ABC extinguisher but it was totaled by the insurance.

 

And I was lucky as a friend of mine had one catch on fire, middle of the night, in his attached garage.   Over $400K in damage.

 

Not the fault of the mechanical switch  suggested at all.   Ford used a pressure activated switch that leaked internally getting brake fluid into the contact area.  Then compounded it the proble by feeding the  cruise control circuit with no fusing.

[FarmerJon]

Here is my mechanical switch,  my pressure switch is still in-line, as a back up.

[harmony]

On 6/22/2023 at 5:08 PM, Sniper said:

Ford uses a similar switch in their cruise control circuit to turn off the cruise when the brakes are applied.

 

Those have been the cause of many, many fires because Ford, in their infinite wisdom, decided it needed to be hot all the time, even when parked and the key in your pocket.

 

Had a coworker almost lose his F-150 due to this thing.  He was fortunate in two cases here.  One, I was standing in front of his truck having a smoke when it started and I noticed the smoke, I ram inside grabbed a fire extinguisher and two, he left the truck unlocked so I was able to open the hood and put it out. 

 

The most interesting thing about it was that he'd already had the recall done to "fix" this issue.

 

My coworker was up a wind turbine with the keys in his pocket when it occurred.

 

So I'd pass on using a Ford switch myself.

So what actually starts the fire?

[Sniper]

46 minutes ago, harmony said:

So what actually starts the fire?

Near as I can figure,

 

the switch is used to tell the cruise control circuit that the brakes have been applied.

 

The circuit is powered all the time.

 

The switch starts leaking internally causing a short, one that doesn't pop a fuse.

 

Eventually, the short heats up enough to ignite the brake fluid causing the fire. 

 

Once it starts it has the contents of the master cylinder to use as fuel until it starts anything in the area to burn.

 

The fix is a new switch with an inline fuse.  This is what my coworker had already had done when his went up in smoke.

[rallyace]

I was under the impression that there was a Harley Davidson part that would fit and have the lights come on with very little pressure on the brake pedal.

[Plymouthy Adams]

6 minutes ago, rallyace said:

I was under the impression that there was a Harley Davidson part that would fit and have the lights come on with very little pressure on the brake pedal.

yes, but at the risk of leaking oil, is it worth it...sorry had to do the dig.....lol

[harmony]

16 minutes ago, Plymouthy Adams said:

yes, but at the risk of leaking oil, is it worth it...sorry had to do the dig.....lol

They're just marking their spot, and the old Panheads did it so very well ?

Edited July 23, 2023 by harmony

[kencombs]

16 hours ago, Sniper said:

Near as I can figure,

 

the switch is used to tell the cruise control circuit that the brakes have been applied.

 

The circuit is powered all the time.

 

The switch starts leaking internally causing a short, one that doesn't pop a fuse.

 

Eventually, the short heats up enough to ignite the brake fluid causing the fire. 

 

Once it starts it has the contents of the master cylinder to use as fuel until it starts anything in the area to burn.

 

The fix is a new switch with an inline fuse.  This is what my coworker had already had done when his went up in smoke.

Exactly right.   My 2000 Expedition caught on fire sitting in front of our store about 2004.   I got to it with an extinguisher very quickly, but it was totaled.  The internal fluid leak was so small that it didn't affect the brakes at all and there was no external evidence of the leak.  Just enough to create a high resistance point in the switch itself. 

[harmony]

That's amazing stuff,about catching fire,,,,, who'd a thunk it.

[kencombs]

49 minutes ago, harmony said:

That's amazing stuff,about catching fire,,,,, who'd a thunk it.

Ford had a huge recall on those, but mine got missed somehow.   Not a rare occurrence at all.   Friend of mine had his catch fire overnight, IN HIS GARAGE.   Huge insurance claim as his house is huge also.