DeTomaso Mailing List: April 99, Message #142

In a message dated 4/5/99 8:40:32 AM, MikeLDrew@aol.com writes:

<< The brake differential pressure switch is just that, a switch. It does not 
block
flow from a broken or ruptured system. >>

You're half-right: the switch portion is in fact just like a brake light 
switch. But the brass 4-hydraulic-line thingy (the actual differential 
pressure valve body) that the electric switch's screwed into, has a brass 
shuttle inside that does the hydraulic circuit leak detection and turns on 
the switch. THAT part does limit fluid flow, get stuck etc. At last Fall's 
tech session when working on Lee Scales' car, Roger had to blow the shuttle 
part back with 100psi air to dislodge it from one end of the valve body..... 
Cheers- J DeRyke