BENDIX TCH-003-027 User Manual

Technical Bulletin

Bulletin No: TCH-003-027 Effective Date: 10/17/2011 Cancels: PRO-03-27-A dated 4/15/87 Page: 1 of 1

Subject:

This bulletin outlines the purpose and function of the Bendix® SV-4™ synchro valve (piece number 109149) in
converter dolly air systems and the vented cut-out cocks in towing trailer brake systems.

Synchronizing Valve

While the synchronizing valve is not required by any regulations, Bendix Commercial Vehicle Systems LLC (Bendix)
has traditionally recommended its use on the converter dolly for the following functions:

• To prevent an automatic application of towing trailer and dolly emergency brakes in the event a breakaway

• Vent air pressure from false charging (service air parking brake release via anti-compounding) on the second

• Assure suffi cient service air pressure for braking is present in the dolly reservoir before permitting supply air to

• Enable faster park and emergency brake applications by locally exhausting air. In this instance, the Bendix SV-4

• The SV-4 synchro valve only – protects towed vehicles from pressure loss when the forward systems leak air.

BENDIX® SV-4™ SYNCHRO VALVE & VENTED CUT-OUT COCK PURPOSE AND FUNCTION

occurs between the dolly and towed trailer. In this instance, the Bendix SV-4 synchro valve acts as a shut-off
valve.

trailer in the event the supply line cut-out cock on the towing trailer is mistakenly closed.

enter the second trailer.

synchro valve acts as a quick release valve.

R-12P™

Valve

PR-3™

Valve

PP-1®

Valve

™

SV-4

Valve

Vented Cut-out Cock

In addition to the synchronizing valve on the dolly, Bendix recommends the use of cut-out cocks with a vented
delivery on towing trailers. Vented cut-out cocks–such as Bendix part number 106118–are also key to preventing
false charging situations. These situations may lead to brake drag when dollies without an SV -4 valve installed or
Bendix® PP-1® dolly valves are operated after it is connected.

© 2011 Bendix Commercial Vehicle Systems LLC, a member of the Knorr-Bremse Group • 10/2011 • All Rights Reserved.

TABS-6™

Module

DC-4®

Valve

TR-3™

Valve

Air disc and drum
brakes shown on the
same axle for pictorial
purposes only.