R and M Diesel Truck Low Air-Pressure Warning Gauge and Signal Service.
Short drive from down town Little Rock, Arkansas
Close to I-30 and I-530.
A low air-pressure warning signal is required on vehicles with air brakes.
A warning signal you can see and / or hear must come on before the air pressure in the tanks falls below 60 psi (or one-half the compressor governor cutout pressure on older vehicles).
The warning is usually a red light and a buzzer.
An older type of warning is the “wig wag.” This device drops a mechanical arm into your view when the pressure in the system drops below 60 psi.
An automatic wig wag will rise out of your view when the pressure in the system goes above 60 psi. 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 psi.
Before air pressure drops to 60 psi, a low air pressure warning signal must activate. On Commercial buses it is not uncommon for the low-pressure warning devices to signal at 80-85 psi.
When air pressure drops to between 20 and 45 psi, the vehicles spring brakes will automatically engage.