Brake assist.

[Quincy]

My 1999 Mountain Aire seems to have a brake assist that drains chassis batt. when key is not removed... told to me by previous owner...wondering if anyone has knowledge of such an issue?

Thanks Q

[BFlinn181]

I think your RV is on a Spartan chassis. The brakes should be either all compressed air powered or maybe air over hydraulic. Neither of those brake systems have any 'brake assist' other than the air compressor on the engine.

I suggest you explore the RV more fully, use Google to search for information about your various installed systems. If you contact Spartan with your VIN, they can provide much information about what they installed on the chassis.

If you still find a phantom drain on the chassis battery system, disconnect a battery cable and use an ammeter to bridge the gap. Take a reading then start pulling fuses until you find which circuit is creating the drain. The dash stereo is one such drain to maintain the presets and clock.

[Quincy]

Thanks for the reply,

The chassis is a Ford F53 with four wheel disc brakes fully hydraulic. The Power assist, I believe, is the power brake pump and you can hear it running if you shut the ignition off and leave your foot on the brake pedal but it stops when you remove the pressure on the petal and no noise is obvious. (This fact tells me the wiring is not correct but I am trying to find out all I can before I get into it.)

I am not sure if this is the reason that is why I asked if anyone has heard of the issue and used the previous owners words.

Q

[Waiter21]

The chassis is a Ford F53 with four wheel disc brakes fully hydraulic. The Power assist, I believe, is the power brake pump and you can hear it running if you shut the ignition off and leave your foot on the brake pedal but it stops when you remove the pressure on the petal and no noise is obvious.

yes... This sounds correct, almost...

With the engine running, the power brakes boost comes from the power steering hydraulic pump .. Its a system called "Hydro-boost"

If the IGN is on, but the engine is not running, or you break a power steering drive belt, or the power steering pump fails, sensors detect the brake pedal and the power steering pressure. If it sees low pressure in the power steering, it turns on the electric boost pump. This electric pump supplies hydraulic pressure to the power brake booster (Not the power steering). This is the pump you hear..


NOTE - On some versions of the Hydro-boost system, Emergency power steering pressure is supplied by a storage accumulator instead of an electric pump.

[n2587n]

the electric pump runs if there in no or low hyd psi like if the engine is not running , if you are driving like down a big hill and the engine stalls you will still have power brakes , if the rv went through a dot insp they would step on the brakes with the engine off if the pump did not run it would need to be fixed to pass , i have seen some times the switch stick and make the pump run with out pushing the brakes , but that is rare .

[BFlinn181]

The hydro-boost should not drain the chassis battery. You should ask a Ford technician if it remains active with the key in the ignition. If the pump cycles on with the key in, sounds like there's a pressure leak that calls for the pump to re-pressurize the system. As a temporary solution, take the key out of the ignition. However, it might be a warning of a leaking power brake system and should be corrected. It's no fun trying to stop an RV with failing brakes.

[Quincy]

Thank you all!!!

I now know what I need to. Based on your answers I dont see the Assist being the culpret anymore and will assume the previous owner was mistaken. I will be looking for a different parasitic loss to the battery. Also meaning I dont have to worry about the brake system for now. The Previous owner just put discs and calipers all around so all is good there.

Thanks again for the help!!!!!

Q