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Installation Supplement for Towed Vehicles Equipped with Electric Hydro-Boost Power Brakes

Unified Tow Brake (UTH-1000 and TVH-1000K)

Some towed vehicles are equipped with hydro-boost assist power brakes instead of vacuum assist, and some of the hydro-boost towed vehicles use a separate 12-volt DC pump for the hydraulic assist. In those applications, you may install the Unified Tow Brake with one minor installation change. We have outlined this change below.

Note: If the towed vehicle is equipped with hydro-boost where the hydraulic assist is coming from the power steering pump, the Unified Tow Brake will NOT work.

Most vehicles equipped with electric hydro-boost power brakes are known as "continuous power brakes." This means that the factory DC pump will energize on its own when needed to keep the power brakes active. If the towed vehicle has "continuous power brakes", no modifications are required to complete the installation of the Unified Tow Brake system.

To check to see if your towed vehicle is equipped with "continuous power brakes":

Raise the engine compartment hood so that you can better hear the factory DC pump, and with the ignition in the towing position, pump the brake pedal. If you hear the DC pump running, this indicates that the vehicle is equipped with "continuous power brakes." If you do NOT hear the DC pump running, proceed with the steps below to connect the UTB violet wire.

When the hydraulic assist is coming from a separate 12-volt DC pump, and the power brakes are NOT continuous as outlined above, follow these steps:

1. Locate the 12-volt DC pump that supplies the hydraulic pressure for the hydro-boost system.

2. Using a test light, identify the wire that goes "hot" when the vehicles ignition is on and is "cold" when the ignition is off.

3. Once you have identified the correct wire, cut the factory wire and install a "blocking diode" (supplied by installer) into the factory wire that will protect the end of the factory wire that goes away from the DC pump.

4. Once the diode is installed, then you can splice in the "violet" wire in the Unified Tow Brake towed vehicle wiring harness that normally would be used to power the vacuum pump to power the hydro-boost DC pump. Install the "violet" wire into the newly installed "blocking diode" according to the diagram below.

When this installation procedure is completed, the Unified Tow Brake Power Module will energize the DC pump when needed to keep the power brakes active and alive.

Form 0811hydroboost (Rev. 11/08)

Example on H3 Hummer

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Last modified: 08/15/11