Unified Tow Brake major issue

[movn-on]

I have installed (myself) and used the Unified Tow Brake (UTB) on two motorhomes and three different Toads over the past fifteen years. I now only have one Toad with a spare UTB system. Yes, there has been problems, but I have been able to work through and solve them with the help of US Gear techs.

All that said, I am finally, stumped. Ready to rip it out and trash it

I have the system on an Acura MDX and it has worked fine for several years. Now it will only works when the MDX engine is running. With the engine running, pull the breakaway and the actuator pulls the brake full on. However, when the engine is not running, the vacuum pump comes on and the actuator is only able to pull the peddle part way down. The pump pulls 15"hg and the voltages from the controller to the actuator are correct in both cases. A US Gear tech suggested that the MDX battery may be too weak, so I replaced it with the largest battery I could stuff in the MDX battery box. Didn't change a thing. All other components and voltages check-out fine. What am I missing

[wa8yxm]

A bad connection somewhere would be my guess.. The heavier wires to/from the controller and the solenoid.

[movn-on]

Thanks for the thoughts. Already ran new 10 gauge hot and ground wires directly from the MDX battery to the controller. Wiring from the controller to the actuator is good and used under both operating condition, engine on or engine off. One possibility, I am now considering, is that the diaphragm in the vacuum booster on the MDX (a 2002) is getting old and requires more vacuum than the 15 "hg the UTB pump draws.

Any car mechanics out there with thoughts on that theory

TIA

[srydve]

Can't comment on the vaccum issue but have you considered the solenoid could be bad? I got my system used with the motorhome and have never been happy with the level of braking it provides, though I think it does provide some. In trying to diagnose what I think is a problem one of my suspects was the solenoid. So far I have not been willing to spend the dollars to test my theory.

[darbyjudy]

I have the same problem with the US Gear unit on my Saturn. I had it on a ford escort and it worked beautifully. But after placing on the 2004 Saturn Vue it does not work as well. I don't feel it braking like it use to on the Ford Escort. I have checked the vacumn pump with a gauge and it shows ok. It just does not pull the pedal down as far. I finally gave up and use as is. If I had to do it over I would buy another type. I called Us Gear and they offered no help since I had the unit for several years.

[wa8yxm]

I do wonder what the "Normal" vacuum is on that system.. And how well the US gear air sucker maintains it.

[movn-on]

The US Gear pumps I have only pull a vacuum of 15 in. hg. Researching various automotive brake systems, the consensus is that a brake vacuum booster requires at least 18 in. hg to operate effectively. I now believe that is the reason my UTB operates perfectly when the engine is running and can't pull the pedal down when only the US Gear pump is working.

I suggest, you check your system by having some one pull the breakaway pin while you watch the brake pedal. Try it with and without the engine running. This will test both your controller, actuator, and the vacuum pump.