Brake light in cold weather, not in warm weather

mukaiboston · Post by **mukaiboston** » Mon Feb 18, 2013 3:51 pm

So I'm at the point of replacing my rear brake switch because I think there is a problem with it not triggering the brake light. Front brake light is fine.
Then I noticed a couple of things that are making me rethink the situation:

1) The brake light always comes on when the temperature drops near or below freezing, but not when it is warmer out. The rear brake does not squeeze as easily in the cold I presume due to the brake fluid getting stiffer. This seems to make the brake light work.

2) In warm weather, if only the rear brake is applied, the light will not come on. If the front brake is applied before or while the rear brake is down, the light will stay on after the front brake is released and before the rear brake is released.

Making me wonder if it is the brake light switch that is the problem (or if there is some other issue with the rear brake shoe, brake fluid or electrical parts). Any input would be helpful as it might save me a good deal of money since I understand that replacing the brake switch is not that simple -- or cheap if it has to go to the mechanic.

Tocsik · Post by **Tocsik** » Mon Feb 18, 2013 5:34 pm

Isn't the rear brake mechanical (cable driven) and not hydraulic?

mukaiboston · Post by **mukaiboston** » Mon Feb 18, 2013 6:24 pm

Tocsik wrote:Isn't the rear brake mechanical (cable driven) and not hydraulic?

I'm really not sure, but I would assume so. I'll I know is that both brakes are different types.

I'm wondering if a worn-down brake shoe would have any effect on the brake light activating?

I just don't want to replace the wrong part because I already had this brake switch "cleaned" of rust once about a year ago and that ran me $75.

Lokky · Post by **Lokky** » Tue Feb 19, 2013 12:31 am

the brake shoe has no impact on the light, the light comes on using a circuit that closes when the brake lever is depressed.

The rear brake is driven by a cable, the front is hydraulic.

The most likely issue is that the connectors are not seated properly for the brake switch to engage, your behavior in cold and hot temperatures to me suggests that the connectors are expanding/contracting enough to not conduct electricity anymore due to a badly seated connector.

agrogod · Post by **agrogod** » Thu Feb 21, 2013 10:36 am

+1 On that diagnosis. Metal contracts when heated and expands when cooled (if I remember my earth sciences correctly).

TVB · Post by **TVB** » Thu Feb 21, 2013 3:41 pm

agrogod wrote:+1 On that diagnosis. Metal contracts when heated and expands when cooled (if I remember my earth sciences correctly).

There are exceptions, but for most materials, it's the other way around.

BuddyRaton · Post by **BuddyRaton** » Thu Feb 21, 2013 4:05 pm

Tocsik wrote:Isn't the rear brake mechanical (cable driven) and not hydraulic?

yes

I agree with checking the connections. May need some cleaning for good contact. I would also hit the switch with some contact cleaner.

mukaiboston · Post by **mukaiboston** » Wed Feb 27, 2013 2:13 am

BuddyRaton wrote:
Tocsik wrote:

I agree with checking the connections. May need some cleaning for good contact. I would also hit the switch with some contact cleaner.
Thanks people. While replacing my speedometer cable which just broke, I discovered that the contacts were not fully plugged under the dashboard. I'll need to put some electrical tape or something in there to prevent them from falling out again.

BuddyRaton · Post by **BuddyRaton** » Wed Feb 27, 2013 1:45 pm

SWEET! I love free repairs! Nice job!