f5fstop or anyone

[Donald Smith]

QUESTION FOR THOSE WITH KNOWLEDGE
I have a H3 I tow behind my diesel pusher motorhome. Tows like a dream. Since I upgraded from a Toy TRD to the H3 I decided to purchase a braking system for safety. In doing research I discovered that the H3 has continuous brake assist, no vacuum assist. Can you explain how this works? I installed diodes at each tail light to prevent any feedback to the electronis. I also remove the brake light fuse so that when the brakes are applied with the braking system in the H3 it will not use the power from the H3 to light the brake light. I amusing brake light power from the RV. I am thinking with brake light power from the H3, I would not have turn signal from the RV. Does the brake light fuse have anything to do with the continuous assist power braking? Does removing the fuse effect the continuous assist? TIA

[f5fstop]

Bascially it is an electric pump that pressurizes an accumulator that supplies the power assist, similar as a vacuum source would for vacuum assisted brakes. Teves uses similar systems, but this system is not Teves.
As to hooking up the H3 brakes for towing, I have no idea, never researched it. I would see if the dealer has ever done a mod like this.

[PARAGON]

what braking system did you buy?

if the H3's has electric continuous power assist, then it means it will have power assist ALL the time. You won't want the normal brake assist that is a dead pedal design.

I doubt pulling the fuse for the brake light will effect the power assist and suspect that you have a separate fuse for the power assist. It might be tied to the ABS.

[Agriv8r]

good info

[Donald Smith]

I am using a brake buddy. One of the the other brands says their system will not work on some vehicles. On the web site they have a link to click on to see the vehicles. I clicked and it said will not work with H3 and some hybrids with continuous assist. So I emailed brake buddy to see if their system will work. The response was yes, just set the air pressure regulator to 10 pounds. The air compressor is built in the system in the tow vehilcle-plugs into acc. plug.
I am asking these questions about the cont. assist because it seems the system is not working after a period of time, like the assist goes away. I am woundering if the assist works only with the key on, is triggered by the brake light switch, do I need to bleed of the assist a set the pressure higher. I got some research to do.

[PARAGON]

It sounds as though it does only work in a Key On position. (sorry I have an H2, just trying to help)

You might need to pump the brakes to "bleed" off the assist each time before you tow and have the brake buddy set to a higher PSI like in a dead pedal situation.

[PARAGON]

here's your solution:

Installation Supplement for Towed Vehicles Equipped with Separate DC Pump for Hydro-Boost Power Brakes

(Includes H3 Hummer)

U.S. Gear Unified Tow Brake (UTB-1000)

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.
When the hydraulic assist is coming from a separate 12-volt DC pump, 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" 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 (PM-6001) will energize the DC pump when needed to keep the power brakes active and alive.
Form 0510hydroboost (Rev. 10/05)

[PARAGON]

Basically, you would provide power to the power assist pump from the RV to keep the pump active.

[Donald Smith]

Thanks Paragon

I had called brake buddy before you posted, all he said was let me know if I figure it out. Got back with him he was glad to have the info also. Time to go looking for the wires.

Don