Wig wag (truck braking systems)

In truck braking systems, one type of warning for low air pressure in an air brake system of commercial trucks is called the wig wag. This device drops a mechanical arm into view when the pressure in the system drops below 60 p.s.i. An automatic wig wag will rise out of view when the pressure in the system goes above 60 p.s.i. The manual reset type must be placed in the "out of view" position manually. It will not stay in place until the pressure in the system is above 60 p.s.i.

Most state CDL (commercial drivers license) manuals describe this term.

ources

* [http://www.dmv.ca.gov/pubs/cdl_htm/sec5_a.htm California Dept. of Motor Vehicle CDL Manual section on air brakes]

As a former trucker, I'd like to say that this system as presented is not exactly correct.It was called a "wig wag" system for the fact two little flags would pop out of the area between the dashboard and front window. These flags then would move back and forth alerting the driver that the air pressure was to low. When the air pressure was above 60lbs, the flags then would be tucked away in their hiding place.

The only place I have ever seen this system is in training videos. This system was done away with probably before 1960. The flag system was then replaced with a system that automatically "pops" the brake buttons on the dashboard. An audible alarm sounds when the air pressure falls below the 60lb level.