2000 Marquis brake light switch

[Jeremy Parrett]

Gerald,
 Can you  tell me where the brake light switch is located?  It is not attached to the pedal under the dash.
 Thanks,  Jeremy

[Lee Welbanks]

Jeremy,

Take a look up under the front of your firewall where the actual air brake valve is with all the air lines connected to it, the switch will probably be teed into your service air line coming from the valve.

[Jeremy Parrett]

I have decided to let Duncan Systems of Elkhart IN check the coach brake systems out tomorrow.
 Beaver Coach Services (Scott) was very helpful suggesting the breaker is one of 11 on the electrical service bay. 
 Apparently there are no fuses .

[Jeremy Parrett]

  We are at Duncan Systems in Elkhart IN.  After 2 hours we still havent located the offending brake light switch.
 We have discovered that the brake lights do work when the engine brake is engaged !! 
  There is no power coming to the brake relay in the service compartment when the brake pedal is pressed.
  Somebody help !!   At $114 per hour we may be forced to drive with a non functioning brake light system.

[Jeremy Parrett]

Hello Lee,
 That makes sense but actually getting up there is a real pita.
 I also know that there is an inline fuse between the 7 pin plug out of the ignition inline to the brake light relay.  Apparenly it is wrapped up in that huge bundle of wires that runs from the dash to the electrical bay.
  As I have brake lights while the engine brake is on I am less worried ,but when I get the coach out of the shop I must spend some time finding this fuse.

[Jeremy Parrett]

As there is no power coming to the brake light relay from the pressure switch, can I run a fused line from the bus to the pressure switch ,assuming I can find it??

[Edward Buker]

Jeremy,

You need to determine if the brake light switch has power being fed to it. If there is no power then you should be able to run a fused wire to the brake switch to bypass the non working switch power feed which would then be disconnected. I am thinking I would feed it from the ignition buss unless you or others think there is a need to have brake lights with no ignition.

If the switch currently has power and does not supply power to the lights with pressure then you need to change that switch.

Later Ed

[Jeremy Parrett]

Hi Ed,
   Now I just have to make like Houdini and find that switch.   
     Thanks for the advice.    Jeremy

[Edward Buker]

May the force be with you :-)

Later Ed

[Jeremy Parrett]

Hi Ed and Lee,
 the tech ran a new fused line to the top (spare) breaker in elec bay and then to the brake light switch.
 We now have brake lights !!