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Author Topic: Air Brakes - low air pressure warning buzzer came on  (Read 10790 times)

Iron Horse

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Air Brakes - low air pressure warning buzzer came on
« on: June 25, 2013, 03:56:49 PM »
2007 Winnebago Journey 36G
We left Chesterfield Virginia on June 16th going to George Washington National Forest (Sherando Lake). We had no problems on the trip. We stayed 7 days and returned on the 23rd. We were almost home on Interstate 288 when the low air pressure warning buzzer came on. The air pressure gauge read zero. The gauge was for the front brake system.  (Gauge number 2) The brakes did not lock up. I pulled off the interstate and after about thirty seconds the gauge went back to 120 psi and we came on home. It happened three or four more times before reaching home. Any suggestions would be appreciated. Thanks
Iron Horse


Changed message icon to Topic Solved
« Last Edit: July 08, 2013, 08:14:11 AM by John Canfield »
2007 Winnebago Journey 36G

Gary RV_Wizard

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Re: Air Brakes - low air pressure warning buzzer came on
« Reply #1 on: June 25, 2013, 04:25:27 PM »
Since the brakes continued to function normally, you have a gauge problem rather than an air brake problem. Perhaps an air leak in the branch line that feeds the gauge, but it could also be an electrical problem causing a reset of the dash gauges. Did all the gauges go to zero or just the front air tank gauge? The warning will come on whenever the gauge drops below a safe level, whether the actual air is low or not. In other words, the alarm is connected to the gauge and not the tank itself.
Gary
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Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

Jim Godward

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Re: Air Brakes - low air pressure warning buzzer came on
« Reply #2 on: June 25, 2013, 06:30:55 PM »
I at sure of the gauges in your MH.  In older Freightliner chassis there problem in the gauging system in that the electronic transducer leads that were soldered to circuit board in a sealed were not soldered properly and became intermittent.

Let me know if this is the type of system you have and I can provide a procedure to repair the sealed box.
Jim
Jim & Pat Godward
AC7PO & KD7ZDM
Hillsboro, Oregon

jagnweiner

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Re: Air Brakes - low air pressure warning buzzer came on
« Reply #3 on: June 25, 2013, 06:50:14 PM »
Jim,

To tag onto the OP's question, I have the problem you describe. My gauges (Freightliner) will zero out intermittently. Some times they come back right away, others they stay at zero or freeze someplace in between. If this is the condition you describe, I'd be interested to know the repair procedure.

My situation is a little different than the OP, as the low air alarm doesn't go off when the gauges go to zero.
-Scott
2000 Itasca Horizon 36LD

bucks2

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Re: Air Brakes - low air pressure warning buzzer came on
« Reply #4 on: June 25, 2013, 07:12:07 PM »
Were it my motorhome I'd do the standard brake check for warnings and  automatic Parking/Emergency brake application to confirm it wasn't an air problem. Then I'd check the air pressure switch which runs the guage. But that would be on my MH which is not a Winnebago so that may not work on a unique machine like a Winnie.


Ken

Jim Godward

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Re: Air Brakes - low air pressure warning buzzer came on
« Reply #5 on: June 25, 2013, 08:19:17 PM »
Jim,

To tag onto the OP's question, I have the problem you describe. My gauges (Freightliner) will zero out intermittently. Some times they come back right away, others they stay at zero or freeze someplace in between. If this is the condition you describe, I'd be interested to know the repair procedure.

My situation is a little different than the OP, as the low air alarm doesn't go off when the gauges go to zero.

Scott,

I don't understand why the low pressure alarm does not go off in this situation.  Does it go off when the pressure is low like when you cold start after a few days????

The information is on the FL Yahoo group, http://groups.yahoo.com/group/FCOC/ in the files under VDU Repair or send me your email address privately and I will return a copy.  Be careful as it involves removing the black box and soldering using ESD rules.

My email is ac7po at arrl.net

Ken,

Always a good practice to do those checks.  We just drove almost 700 miles with the  system off loading about once a minute.  Had a bad governor and check valve.  As long as everything else checked OK, we came home to mechanic and their lower rates.  I told them I suspected governor and I was almost right.  Saved about $500 labor by coming home vs the estimate in WA state. Wish I could still work on the beast!    :(


Jim
Jim & Pat Godward
AC7PO & KD7ZDM
Hillsboro, Oregon

jagnweiner

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Re: Air Brakes - low air pressure warning buzzer came on
« Reply #6 on: June 25, 2013, 08:47:33 PM »
Jim-

Yes, the alarm goes off when the air is below 60 after sitting a few days (as long as the rest of the panel is working). I'll probably just join the yahoo group. Not sure that I want to tackle that repair anyway. It works most of the time and I installed a ScanGauge, which gives me a backup of all the gauges except fuel. Thanks for the info.
-Scott
2000 Itasca Horizon 36LD

Iron Horse

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Re: Air Brakes - low air pressure warning buzzer came on
« Reply #7 on: June 28, 2013, 06:45:51 AM »
Gary thanks for your reply. Only the front brake gauge acts up. It goes to zero and the alarm sounds. The brakes do not lock up. After a few seconds the gauge returns to normal and the alarms stops. I think it is an electrical connection somewhere. The gauges are electrically energized as they come on when you turn the ignition key on. I am going to remove the dash pod to see if I can see any electrical connection. Could be a solenoid valve in the area. I have done the brake check mentioned and everything acts normal. The problem hasn't reoccurred since I have it parked. I think the vibration on the road causes it. I will keep you posted.
Iron Horse
2007 Winnebago Journey 36G

bucks2

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Re: Air Brakes - low air pressure warning buzzer came on
« Reply #8 on: June 28, 2013, 10:49:24 AM »
You do understand that the front brakes will never lock up because they don't have spring brakes on them, right?

I'll put my money on a ground wire not connected well.

ken

Gary RV_Wizard

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Re: Air Brakes - low air pressure warning buzzer came on
« Reply #9 on: June 28, 2013, 01:23:14 PM »
The front tank serves air to all the brakes, not just front wheels. The "front" and "rear" tank designation is a misnomer - the rear provides suspension air (at least in the coaches I have looked at closely). The front tank is probably split, though, with separate partitions for front and rear brakes (called a duplex air brake system, in case it wasn't already confusing enough) so that you won't lose all brakes in case of a single failure.

Are ya sufficiently mind-boggled now?  ;D
« Last Edit: June 28, 2013, 01:25:16 PM by Gary RV Roamer »
Gary
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Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

bucks2

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Re: Air Brakes - low air pressure warning buzzer came on
« Reply #10 on: June 28, 2013, 05:26:16 PM »
Then maybe we ought to bring up primary, secondary and auxillary tanks too?

Ken

Iron Horse

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Re: Air Brakes - low air pressure warning buzzer came on
« Reply #11 on: June 29, 2013, 06:40:18 AM »
Gary, I removed the dash cover and located the back side of the air gauges. There are electrical connections on the back side in addition to the air lines. It is a four pin connector. I removed the one going to the front brake gauge and put dielectric silicone compound on the connector and pins to improve connection. Hope it cures the problem. I won't know until I hit the road again Wednesday. I'll let you know. See Pix
Iron Horse
2007 Winnebago Journey 36G

John Hilley

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Re: Air Brakes - low air pressure warning buzzer came on
« Reply #12 on: June 29, 2013, 11:52:48 AM »
"There are electrical connections on the back side in addition to the air lines. It is a four pin connector. I removed the one going to the front brake gauge and put dielectric silicone compound on the connector and pins to improve connection."

Silicone dielectric compound won't improve the connection. It can prevent moisture intrusion, lubricate any rubber parts and prevent arcing of higher voltage connections
2003 Winnebago Adventurer 38G
605 watts of Solar
1999 Jeep Cherokee Sport
2018 Chevrolet Equinox Diesel AWD
1999 Winnebago Brave 35C
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Iron Horse

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Re: Air Brakes - low air pressure warning buzzer came on
« Reply #13 on: June 29, 2013, 02:21:14 PM »
john didn't realize there were silicone dielectric engineers on the website. preciate it. really do.
IRON HORSE
2007 Winnebago Journey 36G

Iron Horse

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Re: Air Brakes - low air pressure warning buzzer came on
« Reply #14 on: July 08, 2013, 07:57:11 AM »
For what it's worth department, after applying the dielectric compound to the connector and traveling some three hundred miles on Virginia's washboard roads I haven't had any more problems with the gauge.  The compound certainly seems to have helped the connection.
Iron Horse
2007 Winnebago Journey 36G

John Canfield

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Re: Air Brakes - low air pressure warning buzzer came on
« Reply #15 on: July 08, 2013, 08:13:04 AM »
Sounds like reseating the connector was the silver bullet!  Glad it's working for you now, thanks for checking back in.
--John
2005 Horizon 40AD, 2006 Jeep Rubicon Unlimited
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John Hilley

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Re: Air Brakes - low air pressure warning buzzer came on
« Reply #16 on: July 08, 2013, 08:13:55 AM »
I'm not a silicon dielectric engineer, but have designed and built electronic equipment for research and communications in harsh environments for over 45 years. This tells it better than I could do here

Dielectric Grease vs. Contact Enhancer
http://forums.sohc4.net/index.php?topic=82814.0

It has a useful purpose, but that isn't to make a better contact.
2003 Winnebago Adventurer 38G
605 watts of Solar
1999 Jeep Cherokee Sport
2018 Chevrolet Equinox Diesel AWD
1999 Winnebago Brave 35C
  Handicap Lift & Hospital Bed

John Hilley

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Re: Air Brakes - low air pressure warning buzzer came on
« Reply #17 on: July 08, 2013, 10:18:20 AM »
To further the discussion, here are links to a couple of contact enhancers that in theory anyway, make contacts conduct better.

Stabilant 22
http://stabilant.com/techt02h.htm

DeoxIT Gold-G-Series
http://store.caig.com/s.nl/sc.5/category.292/.f

I don't endorse these products, but believe they work when used as intended, they will certainly make a contact more reliable than will silicon dielectric and in most instances provide the benefits of the silicon dielectric.

As John noted, it was possibly the removal and reassembly that cleaned the contact. This is a good practice, disconnect and reconnect a couple of times. Also on quick connect tab type contacts, slightly squeeze the female side to assure good mechanical connections.
2003 Winnebago Adventurer 38G
605 watts of Solar
1999 Jeep Cherokee Sport
2018 Chevrolet Equinox Diesel AWD
1999 Winnebago Brave 35C
  Handicap Lift & Hospital Bed