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Chrysler Repair/No brake lights including center lamp: '05 300C

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QUESTION: Hello! 2005 chrysler 300C 5.7L 47,500miles. Other car driver noticed no brake lights.I have called Chrysler dealer and took car to mufflerman.Mech checked fuses front and rear.He looked under brake pedal,I checked lights.He said it looked okay,suggested changing switch.I know brake pedal light switch dont go bad often,the bulbs seldom fail at same time.I looked at 300C forums-people suggest a stop lamp inhibit relay,suppose to be in rear-cavity 45.I replaced it with new-still no lights.There is a 10 amp fuse in rear for brake lamp(owners manual)10 amp red.I pulled fuse-looks fine,I could replace it anyway with new spare.I have replaced relay in 45 rear,and only fuse I see is in rear(I will Change that) The relay mentioned above is energized when brake pedal used-except if ABS Module says inhibit(thats what I read in forum)
. Dealer cant look at car until next Monday. I am looking for a multimeter to buy. I can check sockets on relays etc.  It would seem to me a switch,or fuse or relay-something like this is more likely the cause,not a wire or relay socket. My ABS light has only come on a few times in past winters from snow and ice on the roads-a dealer replaced a sensor for it once because I was there,they said it could cause the light,it cost nothing under warranty.  What do you think Sir? The car is garage kept all the time,47500 miles.All the other lights work fine,the mech said He could see thru the lense that the brake bulb filaments looked fine. I dont know whether to replace brake switch now,or wait till I get multimeter and check relay sockets,or just take it to dealer.I dont want to go to dealer except last recourse.  Thank you very much for your help,I truly appreciate it!!!!!!!!

ANSWER: Hi Randy,
Thanks for all the details. The brake lights are powered by a 10 amp fuse in socket 19 of the power box. It is possible there is a subtle crack in the fuse's wire so try the spare as a replacement.
The stop switch is at the base of the brake pedal, gray in color, with 6 pins. If you remove the plug and jump from pin 5 to pin 6 of the plug then the brake lights should illuminate. If they do then the brake switch is faulty or out of adjustment relative to the pedal.
The brake light inhibit relay circuit is used in vehicles which have "electronic stability program" as an add-on to their abs system. If you removed that relay (if there is one in the rear box) then that would prevent a false cutting off of the brake lights if you also, after removing the relay, then take a wire and jump from pin 30 to pin 87a of that relay socket (middle pin of the three inboard pins to forward pin of the two outboard pins.
Those are the things to do without a multi-meter.
Thanks for the rating and nomination.

---------- FOLLOW-UP ----------

QUESTION: Thank you Sir,very much for you help. I have a follow-up question please, If when I remove the brake switch plug and jump pin 5 to 6 and they DO NOT illuminate-what does that indicate? The brake switch is okay?    If I remove the brake light inhibit relay then the brake lights should work? Or if I remove the relay and then use the jump wire from 30 to 87A-THEN its suppose to cause brake lights to work? Are you saying if I take the relay out and jump wire 30  to 87A,the brake lights should illuminate? If so,should they illuminate then,or only when I apply brakes?    Or are you saying if when I remove relay-brake lights work-when I push on pedal, then relay is bad?  If I pull relay and jump wire 30to87A -if when I do the jump wire if light come on,the relay is bad or what is bad? I understand the 1st part,about the brake switch,but the 2nd part I dont understand. If I take out the relay,and leave it out-and the lights work,upon depressing brake pedal-I just leave relay out? Please read your explanation of part about the relay again,and make it simpler for me,please. I thank you again very much for your help.

Answer
"Thank you Sir,very much for you help. I have a follow-up question please, If when I remove the brake switch plug and jump pin 5 to 6 and they DO NOT illuminate-what does that indicate? The brake switch is okay?"
First make sure fuse 19 is good by visual check. The following is based upon your not having access to a multi-meter or test light.
No, if you jump from 5 to 6 and they illuminate that means the switch is not good or the pedal is not operating it (out of position). If they do not illuminate that means the problem is further down stream from the switch, i.e. at the inhibit relay or the further wiring to the lights; this assumes that the fuse is good so power is getting to the switch.

"If I remove the brake light inhibit relay then the brake lights should work? Or if I remove the relay and then use the jump wire from 30 to 87A-THEN its suppose to cause brake lights to work? Are you saying if I take the relay out and jump wire 30  to 87A,the brake lights should illuminate? If so,should they illuminate then,or only when I apply brakes?    Or are you saying if when I remove relay-brake lights work-when I push on pedal, then relay is bad?  If I pull relay and jump wire 30to87A -if when I do the jump wire if light come on,the relay is bad or what is bad?"
The relay when it is not activated is supposed to do the jump from 30 to 87a, So if you remove it and step on the brake then they definitely will not illuminate, but if you do that jump, after having resolved the brake switch issue, and they do then illuminate when you step on the brake then for sure the brake switch is good, but then that relay is either defective or it is being falsely activated by the abs system. That will need a multi-meter to tell you which.

"I understand the 1st part,about the brake switch,but the 2nd part I dont understand. If I take out the relay,and leave it out-and the lights work,upon depressing brake pedal-I just leave relay out?"
No, the brake lights definitely won't illuminate with the relay out. A jumper or a properly working relay will cause the brakes to illuminate when you step on pedal. The relay, when properly working allows the brake lights to illuminate when it is NOT activated, and to not illuminate when activated. Thus, an "inhibit" relay.
I hope this clarifies things.

You can do another rating and nomination if you would be so kind.
Roland

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Roland Finston

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Get a Free Fast answer to your repair question about a Chrysler/Dodge/Plymouth car, minivan, SUV, or truck. Problems with electronically controlled engines and transmissions as well as body wiring problems are my specialty. This free troubleshoot advice forum helps you diagnose faults, minimize repair costs or do-it-yourself.

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