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Author Topic: What is this electrical connection on my air brakes drier unit?  (Read 799 times)
Mex-Busnut
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« on: December 07, 2011, 09:54:10 PM »

Dear Friends,

My bus did not have a drier installed from factory, and when we rebuilt the brakes a few months ago, my diesel mechanic insisted it would be very beneficial to add the drier or "purger" as he calls it. Anyway, it was installed back then.

Now that I am doing some other things in this bay (shared by the engine's radiator), I noticed this drier unit has an electrical connection on it and behind that, it looks like a small D. C. motor or maybe a solenoid? What would this be, and for what purpose? it is not connected to anything at the moment.

The connector can be seen in the photo just below the brass-colored valve. The "D. C. motor" to the right of the drier unit's body.
Thanks in advance!
 
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Dr. Steve, San Juan del Río, Querétaro, Mexico, North America, Planet Earth, Milky Way.
1981 Dina Olímpico (Flxible Flxliner clone), 6V92TA Detroit Diesel
Rockwell model RM135A 9-speed manual tranny.
Jake brakes
100 miles North West of Mexico City, Mexico. 6,800 feet altitude.
Oonrahnjay
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« Reply #1 on: December 07, 2011, 10:17:24 PM »

     I can't quite see the photos and your dryer is different from mine, but that is almost certainly the heater connection.  There is a small electrical heater right at the purge valve (near the outlet) that stops water vapor from freezing and jamming the valve open.  If this happens, there is no air delivered to the tanks.  What is the lowest temp that you'll ever see?  If you're SURE that you'll never be in temps below 35 degrees F, then you wouldn't need the heater but for most of us, we'd be crazy not to get it working.   (Note:  Most of them have a thermostat built in so, even if the electrical supply has no switch or the switch is left on, it will not draw electricity and activate the heater until it see temps down near freezing.)

     If someone is more familiar with your model air dryer and I'm wrong on any part of this, please correct it.
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Bruce H; Wallace (near Wilmington) NC
1976 Daimler (British) Double-Decker Bus; 34' long
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bevans6
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« Reply #2 on: December 08, 2011, 05:18:01 AM »

The air dryer has a heater, that's what that is.  Moist air rushing out a venturi (the purge valve) can easily freeze at quite warm temperatures, albeit temporarily, but the main risk is indeed temperatures well below freezing.  The air discharged towards the air dryer by the compressor is itself quite warm.  I wouldn't put this one at the very top of your fix-it list, but it's a good thing to remember.

Brian
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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
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luvrbus
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« Reply #3 on: December 08, 2011, 05:50:02 AM »

You can buy the harness from RyderFleet for 8 bucks plug it wire and it so it powers when the switch is on if the dryer needs it turns the heater on automatically when the temp is low not a priority but why waste the dryer features

good luck 
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buswarrior
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« Reply #4 on: December 08, 2011, 05:57:06 AM »

As above, it's the heater connection.

Is there a name on it anywhere? It isn't a Bendix AD 1,2,4 or 9.

happy coaching!
buswarrior

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luvrbus
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« Reply #5 on: December 08, 2011, 06:00:19 AM »

Looks like a Wabco or Haldex to me BW good driers anyway
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gcyeaw
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« Reply #6 on: December 08, 2011, 08:07:37 AM »

  If it were me I would want it connected. One unexpected cold snap could ruin a trip, and who wants to do a wiring job with frozen fingers in the dark at the side of the road?  Unless your coach is already wired for it, I would use a relay activated by the ignition switch circuit. Adding loads to the ignition directly can result in overloading the switch contacts and failure down the road.

  On my Bluebird I was loosing voltage across the ignition switch. When I looked I found the supply side wire insulation was melted back an inch or so due to the heat generated by the old/poor connection. After repairing it I added relay's to the output side so the main loads are carried by the relays, not the switch. I did the same with the headlights after the original switch burned out.  Big diffeence in brightness and the switch should last forever.
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Gardner
1983 Bluebird FC.
Mex-Busnut
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« Reply #7 on: December 08, 2011, 06:59:18 PM »

Looks like a Wabco or Haldex to me BW good driers anyway

My drier is definitely a Wabco. Which number is the model number? Check out the pictures and let me know what you think.

What kind of servicing does this take? A filter?

Fear not: The bottom air hose was temporarily disconnected to lay in the plywood, and will be back in place tomorrow!

Thanks to all for helping with info!
« Last Edit: December 08, 2011, 07:01:33 PM by Mex-Busnut » Logged

Dr. Steve, San Juan del Río, Querétaro, Mexico, North America, Planet Earth, Milky Way.
1981 Dina Olímpico (Flxible Flxliner clone), 6V92TA Detroit Diesel
Rockwell model RM135A 9-speed manual tranny.
Jake brakes
100 miles North West of Mexico City, Mexico. 6,800 feet altitude.
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