No brake lights

ALMANY

MEMBER
2005 CHRYSLER 300
5.7L
V8
RWD
AUTOMATIC
47,000 MILES

All other lights work. No brake lights either side. Also, when lock/unlock pressed on ignition key-only lights that come on at rear is backup lights. I pulled fuse cover in trunk. Cavity 15 (brake lamp 5.7L) empty! Cavity 19 had good red 10 amp. Installed new 20 amp yellow in Cavity 15-still no brake lights. Also, there is black square relays/switches in spaces 24, 45, 46 that dont even appear in owners manual! ( They were warm to touch so I know they have some purpose. I installed a new relay in Cavity 45-no lights still.I took car to mech at local mufflerman where I have had service before. They checked fuses front and rear with meter-they said all okay. The mechanic noticed there was not bottom metal contact in Cavity 15 to begin with(I dont know why Chrysler gives you a owners manual that is inaccurate and incomplete. The mechanic suggested I could replace the brake switch under pedal for $55. I called dealer to find out about this"stop lamp inhibit relay( I saw a website that stated failure of this relay would cause all 3 lights to fail. I called dealership, they said their software only shows the relay in front and back, but not their function. How can that be. This should not be this difficult to diagnose.I made an appointment to have my car put on their machine at dealership-$100 which they apply to repair bill. I didnt go back to mechanic to have the brake light switch replaced. It was simply a replace and see if it fixes the problem, I chose not to guess. How likely do you think it is switch not relay? How about bulbs? The mech didnt pull off cover in trunk because He said he could see the filaments-which he said were okay. Are brake lamp filaments and running light filament in same bulb? Do you have links to accurate diagrams that show what relay goes where? Thank you very much for your help!

PLEASE HELP! Thank you very much!

7 Replies

JACOBANDNICKOLAS

MECHANIC
108,179 POSTS

Hello,

There is a stop lamp inhibit relay in the TIPM under the hood I think is out. Here are guides to help you do the test.

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

and

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

Check out the brake wiring diagram and fuse panel identification below so you can see how the system works.

But before you do anything, I would check the brake light switch. It isn't hard to do. There are two wires to it and one is a power supply and the other sends the power to the lights. I would suggest just checking of there is power available to the switch. If there is, actuate the switch and check if there is power out. Not a difficult process. Also, I have seen many times over the years where the switch has come loose or disconnected. As a result, pressing the brake pedal won't actuate it.

This is the what I would suggest first. And yes, there are bulbs that have two elements in them. One functions for the parking light and the other for the brake and turn signal.

One last thing, I do have access to wiring schematics, but I can't copy and paste. If you can give me specifics, I will try guide you.

PS: Again, check the switch first before taking it to a dealer. I feel that is where the problem is coming from.

Check out the diagrams (Below)

Please let us know what you find. We are interested to see what it is.

Cheers Joe

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