Vacuum pump for Unified Tow Brake
I have been using the US Gear Unified Tow Brake in my last two tow vehicles, and now want to install it in a third. Unfortunately, it seems as if the vacuum pump has failed: testing the system befor...
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i finally installed a generic vacuum pump (ACDelco 20804130 GM Original Equipment Power Brake Booster Auxiliary Pump Assembly, from Amazon), and it seems to operate the brakes OK. I installed it in place of the original US Gear pump, but because it draws quite a lot more current than the original I used an inexpensive automotive relay (with snubbing diode!) to drive it.
The pump runs when it should, and the brakes come full-on when I pull out the breakaway switch, suggesting that it works.
But I have another issue, one that may or may not be related to the pump. The "proportional" feature of the system no longer operates: the brakes are either off or fully on - on when braking in the motorhome, off when driving normally. The motorhome unit and the car controller seem to be communicating OK judging by the indicator lights in the MH, and the manual lever in the MH brings on the car brakes fully. But when I operate the MH brakes, there is a second's delay then the car brakes come on fiercely, resulting in quite a severe jerk (and probably stress on the towing system).
While I have still one or two things to try, I wondered whether anyone has seen this, and I would welcome suggestions to help me decide whether it is a fault in the MH unit or the car control unit. Or whether it's just a matter of adjustment.
Thanks.
The pump runs when it should, and the brakes come full-on when I pull out the breakaway switch, suggesting that it works.
But I have another issue, one that may or may not be related to the pump. The "proportional" feature of the system no longer operates: the brakes are either off or fully on - on when braking in the motorhome, off when driving normally. The motorhome unit and the car controller seem to be communicating OK judging by the indicator lights in the MH, and the manual lever in the MH brings on the car brakes fully. But when I operate the MH brakes, there is a second's delay then the car brakes come on fiercely, resulting in quite a severe jerk (and probably stress on the towing system).
While I have still one or two things to try, I wondered whether anyone has seen this, and I would welcome suggestions to help me decide whether it is a fault in the MH unit or the car control unit. Or whether it's just a matter of adjustment.
Thanks.
