Brake light problems
Thread Starter
|
Junior User
Joined: May 2007
Posts: 85
Likes: 0
Brake light problems
2003 F250 Lariat FX4 7.3L diesel automatic
Having problems with the brake lights- the brake lights in the tail lights don't work when the pedal is pressed, but the CHMSL (third) brake light comes on. When you activate the turn signals the bulb in the tail lights function as they should. This tells me the bulbs and wiring going to the turn/brake light bulbs in the tail lights is good. And because the 3rd brake light works, it tells me the fuse and brake switch are good. This leads me to believe that the multifunction/ turn signal switch is bad( or the brake light wire supplying it). The power for the third brake light goes to the light before it goes through the turn signal switch, so it still works properly. But I don't think the power is coming through the turn signal switch. Can somebody confirm my thinking before I tear the column apart? Also want to have new switch on hand before I tear it apart.
Having problems with the brake lights- the brake lights in the tail lights don't work when the pedal is pressed, but the CHMSL (third) brake light comes on. When you activate the turn signals the bulb in the tail lights function as they should. This tells me the bulbs and wiring going to the turn/brake light bulbs in the tail lights is good. And because the 3rd brake light works, it tells me the fuse and brake switch are good. This leads me to believe that the multifunction/ turn signal switch is bad( or the brake light wire supplying it). The power for the third brake light goes to the light before it goes through the turn signal switch, so it still works properly. But I don't think the power is coming through the turn signal switch. Can somebody confirm my thinking before I tear the column apart? Also want to have new switch on hand before I tear it apart.
Fleet Mechanic
Joined: Oct 2017
Posts: 1,704
Likes: 164
From: Southwest Ohio
I do not believe that the brake switch sends any signal through the turn signal stalk. Are the brake light/tail light bulbs dual-element bulbs? The turn signal/tail light uses only one element and the brake light uses both (which is why it's brighter). Since bulbs usually have a set life span, when one dies the other typically goes soon thereafter.
-- Dave
-- Dave
Postmaster
Joined: Nov 2015
Posts: 4,807
Likes: 125
From: Colorado Springs
Well, have you actually checked the bulbs? How did you notice the lights weren’t working? One could have been burned out for a while and you only noticed it when the second bulb burned out. If they had been previously replaced as a pair, it would make sense that they could burn out as a pair. That’s the easiest place to start..
Hotshot
Joined: Jan 2004
Posts: 19,763
Likes: 1,082
From: St Louis
This leads me to believe that the multifunction/ turn signal switch is bad( or the brake light wire supplying it).
If the rear bulbs work properly for their turn signal functions, there is nothing wrong with the circuit from the MFS rearward including the bulbs. Both of the above responses are incorrect in their assessment and "understanding" of how the circuit works.
Check the light green wire into the MFS for the brake signal when the pedal is depressed. If present, the MFS is defective. If missing, there is a wiring concern in that LG wire between the MFS and the BPP switch. A not uncommon failure is for the wire to break inside the insulation close to the BPP switch, it's harder to find.
Thread Starter
|
Junior User
Joined: May 2007
Posts: 85
Likes: 0
You are correct.
If the rear bulbs work properly for their turn signal functions, there is nothing wrong with the circuit from the MFS rearward including the bulbs. Both of the above responses are incorrect in their assessment and "understanding" of how the circuit works.
Check the light green wire into the MFS for the brake signal when the pedal is depressed. If present, the MFS is defective. If missing, there is a wiring concern in that LG wire between the MFS and the BPP switch. A not uncommon failure is for the wire to break inside the insulation close to the BPP switch, it's harder to find.
If the rear bulbs work properly for their turn signal functions, there is nothing wrong with the circuit from the MFS rearward including the bulbs. Both of the above responses are incorrect in their assessment and "understanding" of how the circuit works.
Check the light green wire into the MFS for the brake signal when the pedal is depressed. If present, the MFS is defective. If missing, there is a wiring concern in that LG wire between the MFS and the BPP switch. A not uncommon failure is for the wire to break inside the insulation close to the BPP switch, it's harder to find.
Thread
Thread Starter
Forum
Replies
Last Post
TexanAmmo
1987 - 1996 F150 & Larger F-Series Trucks
22
Jul 22, 2018 02:31 PM
orlando.ortiz3
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
5
Mar 15, 2018 12:27 PM
weldworks54
1973 - 1979 F-100 & Larger F-Series Trucks
15
Jun 27, 2010 06:36 PM
shane43028
1973 - 1979 F-100 & Larger F-Series Trucks
7
Aug 20, 2003 10:15 PM
