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Old 01-26-2012, 02:06 PM   #1
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Brake Safety Problem w/Key Off

At the 2012 Quartzite Rally we identified a systematic problem that may affect many Alpine's excluding Avalanches (as they have air brakes, not Bosch HydroMax brakes).
Majority of model years affected appear to be 2004 & 2005. However, a 2001 reported a similar problem. I recommend all Alpine owners check the brake function as follows:
You are listening & feeling for whether the electrical aux brake boost is present with Key-Off (KOff) and with Key-On-Engine-Off (KOnEOff), and stepping on the brake pedal. If you step on the brake pedal and it reacts like a brick, no movement & no electrical pump noise, then you have the issue. On 05's we checked, w/KOnEOff- the pedal depresses and the grinding noise of the electrical aux boost pump could be heard, but w/KOff there was no aux brake boost!!
The reason this is a real safety problem is that if park brake is disabled for any reason, the usual reaction when the coach starts rolling is to jump in the driver's seat & press like hell on the brakes; if there is no boost, there is very little braking power, and an inversely proportionate rate of panic. Coach rolling w/out stopping power is not so good

Under any condition of key, the electric aux brake boost should be present, until the engine is running and creating hydraulic boost (& steering assist). Once engine runs the hydraulic pump, the electric aux pump should drop out as it is not needed. This function is controlled by signal to a 4-pin bosch-type relay located next to the HydroMax master cylinder assembly. In the case of 04-09 rigs, relay is above and on a section of fore-aft oriented firewall bulkhead. On 97-03 rigs I believe but have not verified, the relay is above HydroMax (which is below driver floorboard) and on DS frame rail; YMMV. This OEM relay has 4 wires in, one fat white, one fat red, which are switched-within-relay 12V feed to the pump, and two skinnier white wires which activate the coil; one coil wire is grounded and the other is waiting for +12V to activate the coil & switch the pump on. To find which coil wire is which, I apply breakered 12v to each coil wire, and one runs the aux pump (applying brakes) if relay is good and pump wired correctly; the other pops the breaker as it is direct to ground w/no resistance.

For Vansco (2004-09) model years, we determined at DRRXI that the problem is bad programming in the Vansco by OEM; brake pedal signal is showing on Input LED 24 on front Vansco under all conditions, but Output 18 LED on rear Vansco is not lighting to enable pump relay. I have cobbled up the attached bypass fix. It takes a new 5-pin relay, some terminals, coupla 3A fuses and some wire, plus maybe 2 hours labor if you don't screw around studying stuff like I do. We only found the problem on 04 & 05 Vansco rigs, but doesn't mean others don't have it.

On the 2001 rig, there was no aux pump function whether KOn or KOff. If that is true, the feed to the pump may have been miswired from the factory or may have been damaged in the interim. For that rig's situation, I added note (4) at the bottom of schematic attached, noting that relay signal if adding the fix should be from +12V that is only active with engine running. Of course for a rig w/no aux pump function, first you should suspect bad wiring which could be wiring from chassis controls to the aux pump relay, burned out relay, or wiring from relay to pump; could also be bad pump motor. Diagnostics are required for this condition.
Attached Files
File Type: pdf 2004-05 Brake fix 1.26.12.pdf (1.20 MB, 179 views)
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Old 01-27-2012, 09:48 AM   #2
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Mike, Great mod I will be doing this soon. I had a close call last spring while cleaning the inside of the windshield. I released the service brake by bumping it with my hip while leaning over the dash. The coach rolled about 10 feet before I got the key on and the coach stopped. No injuries or damage but it could have been disastrous. I use chalks now when parked on off level site.

Below is a link to high quality automotive wire. I keep several colors on hand for these kind of projects. They have a minimum length of 20 feet in the small gauges. I am sure there numerous sources for good quality wire. I just find this to be convenient.

Automotive wire, Automotive electrical supplies, connectors, relays, switches.
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Old 01-27-2012, 12:37 PM   #3
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Chocks is a good idea regardless as a failsafe. The guy who nearly plunged into the Sacramento River w/his 05 had just removed his chocks and was putting them in the basement when he realized the coach was moving. He got it stopped but not w/out some moments of terror.

I installed the steering kit for him and when I moved his coach onto the street I realized he had no brakes w/key off, and he relayed the story to me. Been trying to define the scope of it since, and at Desert Rat 11 we found enough coaches w/the issue that I figured this thread was warranted and some semblance of a fix needed.

I should have mentioned earlier- diagnose all instances of no-aux-boost prior to implementing any fix. The PDF above is only good for no-aux-boost w/key off, but aux-boost present under all other conditions. If any other condition, some variant of the fix is needed based on actual coach wiring. I give a suggestion in note (4) for one alternate condition, but actual diagnosis is needed in all cases (which diagnosis isn't exactly rocket science) to determine extent of problem if any.

For my own safety pre-flight check, and occasionally while parked for a while, I step on the brake to hear the aux boost pump and make sure its working while KOff, or KOnEOff, and I do the same any time I move somebody else's coach.
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Old 01-27-2012, 05:42 PM   #4
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Luckily this is not an issue with earlier coaches that use hydraulic parking brake release. Unlike the coaches with air release you cannot release the parking brake unless the engine is running. It is still advisable to check that the backup motor works without the engine running as an engine stall going down the highway could still leave you without brakes.
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Old 01-28-2012, 11:21 AM   #5
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Interesting discussion this AM about this parking brake situation. For those with the Vansco "wiring problem" and air actuated parking brakes--if you did manage to "bump" the yellow pull handle, the only way the brakes will release is if there is still some residual air in your air tank. If there is and you do manage to bump the brake off, them simply pull the handle again--the air from the brake actuator is dumped and the spring-loaded brake shoe is immediately re-applied [Remember -- it takes compressed air to release the parking break but no air is required to apply it]. Realize this doesnt resolve the root cause, and it is difficult to remember these things in an emergency but unless you are plunging over a cliff at a high rate of speed, simply pulling the yellow handle back out should stop you in most cases.
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Old 01-30-2012, 03:56 PM   #6
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Smith on Safety ::WELCOME:: - This works to keep the yellow Emergency/Parking Brake from being depressed, however, it would have to go in from the top and upside down. It comes with a magnetic clip so it will stay on the steering column when not in use. You could then fashion a little keeper on it, so an inquistive child would not be able to remove it.

Or you could use a little small wood clamp as sold at Home Depot or Lowes, you will have to experiment with the size. Basically you want something to keep a dog, small child, or even you or BH bumping up on this knob and depressing it.

Another thing which can be done is to bleed off all available airpressure in the system, so even if the knob is pressed, there is not enough air pressure in the system to depress the spring which would release the brakes. This can be accomplished by just opening up one of the air chucks located in various places on your coach, once the air is gone, the yellow handle wont release. Again, wheel chocks are positive insurance the coach won't roll, and I use them when parked in a place which is possible to have the coach roll if I lost that parking brake, this would include, rest areas while stopping for a wake up coffee, and or campgrounds where the terrain is not level. On very steep places, I always use a chock, as I don't trust the parking brake to hold the coach, and as far as I know, no positive information has been published on it's adjustment or maintenance.

Thank you EM for the update and diagram. If the 01 Coach has not been repaired I will call the owner and give him a hand, since we are in Yuma.
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Old 01-30-2012, 09:02 PM   #7
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Ran into another 2004 this afternoon w/no aux boost when KOff. Looks like more than a few 04's are involved.
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Old 01-31-2012, 10:30 AM   #8
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Mike et al,
Last summer when I was having a brake controller installed, we noticed this problem. Cummins in Coburg ran a wire from the pedal pins out through the firewall to the brakes and now all works fine- as it should.
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Old 02-01-2012, 01:25 PM   #9
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Dave- If they ran that direct to the aux pump activation relay, then the chassis hydraulic pump would be providing boost while driving in addition to the aux pump. I thought about that and that wasn't the OEM boost logic, so I didn't want to interject potential for backfeeding the aux pump and maybe making a problem for its valving (I don't know if there is any possibility of a problem from that, but it would take its own investigation). Instead the schematic is set up to provide power to the aux pump relay only in the instance when the OEM programming failed to do so but should have; while engine is running or aux pump is otherwise enabled, the above setup eliminates any competition for running the pump or from the engine's pump.
That may have been what Cummins did, but doesn't sound like it from the description you gave. If it isn't, I wouldn't worry about it until you are in for other service anyway, but perhaps have it checked then. Could also be my preoccupation w/competition is baseless. You can give me a call to discuss.
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Old 02-28-2012, 01:54 PM   #10
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Mike, I have started the rewire of my brakes. One question, I have found the terminal that is ground key off and 12V key on. It is also 12 volts with engine running. I see no reason for that to be an issue. I also found what appears to be diode on the #18 wire going to the Hydroboost relay. Should put the Tee connection before or after the diode.
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Old 02-28-2012, 09:11 PM   #11
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i'd put the Tee between diode & HMax relay. Since this circuit is wired NC vs the Key, as soon as the key is On the circuit should moot itself, sadly unlike certain politicians we could name.
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Old 02-29-2012, 04:34 AM   #12
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Thanks Mike, makes sense to me. What is the trick to getting the red tab out of the brake switch connector? Any links available with tech info on the connector. I googled F81B-14489-A (the number on the connector). I had no luck finding the
installation instructions for the terminals into the connector housing.
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Old 02-29-2012, 11:30 AM   #13
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I found a pair of round nose pliers in my pile of trash that had a nose end about the size (very small) to fit into a squarish pocket recess created between the tan connector body & a rib on the red tab. At that, it was a hard press against red, small pry, wiggle, hard press on other side, small pry, wiggle, repeat type process. Magnifying head gear would be a help, and patience is key. The red plastic seems fairly malleable, and you could ruin it w/too much force, at which point I suppose you could try to drill it out?
It isn't really needed, and I'm now driving w/out it (I figured I'd add in the pins when I find a set, then reassemble). The pins all snap into place anyway, so its purely a double safety.
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Old 02-29-2012, 12:33 PM   #14
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I was able to get mine to snap in so I am good. Wiring is complete and functioning as designed. I just need to tie everything up. Thanks for designing this fix for us.
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