Hazards not working on a 3540PST/wcab

[chirp22]

3540PST/w cab. Turn Signals work, Hazards do not. Found the Hazard/Turn Signal relay behind the dash (3 prong). With Hazards off, have +12V on the B Terminal. When Hazards on - no +12V on the B Terminal. There is a Hazard fuse in the cab and it is good (checked with VOM). Have +12V at the fuse. Have replaced the Hazard switch with a new one - same results. Only other items in the path are the relay (doesn't make sense that relay will work with turns and not hazards) or the turn signal combo switch itself. Relay is about $50 and turn signal combo switch is about $50. Any thought on where to go next?

 

[Joe Hickerson]

...may be an errant separate ground on the hazard side of the relay.

 

[Joe Hickerson]

....oh, and blinker fluid may be low!!

 

[chirp22]

...may be an errant separate ground on the hazard side of the relay.

Never thought of that. Would think +12V straight to ground would blow a fuse somewhere. Plan to check the L port on the relay connector with a VOM to see what I have when the Hazard is on. The lack of +12V on the B port when the Hazard is on is perplexing. I could think +12V would always be present for turns and hazards to work.

 

[chirp22]

....oh, and blinker fluid may be low!!

Thinking 0W40 or 10W40 blinker fluid?

 

[Joe Hickerson]

Thinking 0W40 or 10W40 blinker fluid?

0W winter, 30W summer. Maybe someone will post with an electrical schematic.

 

[Thomas]

Have trace wires one maybe damage and still not popping the fuse.

 

[chirp22]

Attached is the 3540PST/wcab electrical diagram. It's kinda hard to read when blown up, however, the switch diagrams do not make sense. The Hazard switch shows one turn signal connected and one not connected (makes no sense). Also, the +12V coming to the switch, if I understand how that switch works, would go away when the switch is pressed (which makes no sense). If you guys know something different about how these switches work, I'm all ears.