Turn signal but no brake

Have you done any work on the coach recently?

I assume this is without a toad connected?

There might be a brake-light plunger switch on the brake pedal assembly.

if air brakes there is a switch in system for lites.Usually round with 2 wires mine was right by the treadle valve.mine had two of them.

It sounds like you have the wrong bulb or a broken one. Easy to test with a cheap 12 volt tester. One that lights up when it makes connection.Just ground the clip and poke the base of the bulb socket after you remove the bulb.

Take the bulb out and compare it with the one that works. Look for two contacts on the base. Some systems use a seperate bulb for the brakes and some use a dual filament bulb. A dual filament is very common.

turn 4 way flasher on see if it works probably a turn signal switch problem

I would go with Dave's suggestion. 2 brake switches maybe. That would be a good setup as if one switch goes bad you still have at least one brake light. Could be near the brake pedal either inside or out. Or possibly if you have an electrical control center outside under drivers seat. Good luck

Assuming you are correct about the same filament for brake and turn and it works with the four way flashers, it's in the blinker switch on the steering column. Hopefully you will not have to pull the steering wheel.

*If in doubt about this, try wiggling the blinker switch with the brakes on and someone watching... this may make it work some of the time. You may even be able to bend the contact back into place without replacing. Air brakes does not change what's a fairly simple electrical system.

You're assuming the brake light and turn signal use the same WIRE to activate the lamp. They are not. Remove the SOCKET and using a meter, check for power on the turn signal wire, then on the brake signal wire. If one does not work, then your issue is in the wiring. If they both work, then change out the bulb and/or socket. If it's in the wiring, start at the brake pedal and work backwards until you find the problem. You'll only have one fuse for the brake system wiring...Dennis

Call the Freightliner help desk 1 800 FTL-HELP. It's a free service. Have the last 6 digits of your vin number available.

They will look up the wiring diagram for your specific coach, and can give you advice on where to look for the problem.

I think IVYLOG has the best theory so far.

Fred

Wonder if the OP found out what was wrong...:h:h:h....Dennis