| Electro level down switch running pump [message #330190] |
Tue, 20 March 2018 22:21  |
Tilerpep
Messages: 404
Registered: June 2013
Location: Raleigh, NC
Karma: 7
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Senior Member |
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Started diagnosing the 78 air suspension system. Found a clear leak at connection to bag shut off valve. Also found a slow leak through one height valve dump nozzle which I may have to clean/disassemble to see if usable.
Question: when I have the electric switches in hold, and hit the "down" buttons, they turn on the air pump, is that right or a sign of problem. (Up button turns on pump and tries to go up, but weak original Dana pump and the above mentioned leak not very effective). With down switches, one side is venting as expected and the other is not reliably activating the release solenoid, so something is not connecting right. But as I dig in, I don't know if I am supposed to get the pump going up to pressure AND venting/exhaust (should be possible I think, a pressure side, and release from the bags).
I found this
http://gmcmotorhome.info/levelsch.htm#HEIGHT
but i'm not picking out my answer as of yet
1975 Glenbrook, 1978 Royale rear bath
Raleigh, NC
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| Re: [GMCnet] Electro level down switch running pump [message #330191 is a reply to message #330190] |
Tue, 20 March 2018 22:28  |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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TYler'
It is normal to have the compressor run even when lowering the coach.
I'm not into it enough to expain why.
On Tue, Mar 20, 2018 at 8:21 PM, Tyler wrote:
> Started diagnosing the 78 air suspension system. Found a clear leak at
> connection to bag shut off valve. Also found a slow leak through one height
> valve dump nozzle which I may have to clean/disassemble to see if usable.
>
> Question: when I have the electric switches in hold, and hit the "down"
> buttons, they turn on the air pump, is that right or a sign of problem. (Up
> button turns on pump and tries to go up, but weak original Dana pump and
> the above mentioned leak not very effective). With down switches, one side
> is
> venting as expected and the other is not reliably activating the release
> solenoid, so something is not connecting right. But as I dig in, I don't
> know
> if I am supposed to get the pump going up to pressure AND venting/exhaust
> (should be possible I think, a pressure side, and release from the bags).
>
> I found this
> http://gmcmotorhome.info/levelsch.htm#HEIGHT
> but i'm not picking out my answer as of yet
> --
> 1975 Glenbrook, 1978 Royale rear bath
> Raleigh, NC
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.appliedgmc.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: Electro level down switch running pump [message #330193 is a reply to message #330190] |
Tue, 20 March 2018 22:53 |
rvanwin
Messages: 325
Registered: April 2007
Location: Battlefield, MO
Karma: 6
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Senior Member |
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Tilerpep wrote on Tue, 20 March 2018 22:21Started diagnosing the 78 air suspension system. Found a clear leak at connection to bag shut off valve. Also found a slow leak through one height valve dump nozzle which I may have to clean/disassemble to see if usable.
Question: when I have the electric switches in hold, and hit the "down" buttons, they turn on the air pump, is that right or a sign of problem. (Up button turns on pump and tries to go up, but weak original Dana pump and the above mentioned leak not very effective). With down switches, one side is venting as expected and the other is not reliably activating the release solenoid, so something is not connecting right. But as I dig in, I don't know if I am supposed to get the pump going up to pressure AND venting/exhaust (should be possible I think, a pressure side, and release from the bags).
I found this
http://gmcmotorhome.info/levelsch.htm#HEIGHT
but i'm not picking out my answer as of yet
Do you have an electro level 1 or II system? Typically, a '78 is Electro Level II and has two pumps, one for each side with no air tank. I'm not sure about how it operates but I do not believe the pumps will come on when lowering. Sounds like from your description, you have an Electro Level I. If that is the case, then the one pump will come on when you press the lower buttons just as you describe - that is the normal operation. The switches sometimes get corroded and need to be cleaned. Remove and spray with contact cleaner while working the switch. Many times, this will "fix" a problem where a solenoid is not responding. When lowering, the pump runs to pressurize the air tank. If air tank is already pressurized, then the pump will not come on.
Randy & Margie
'77 Eleganza II '403'
Battlefield, MO
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| Re: Electro level down switch running pump [message #330200 is a reply to message #330190] |
Wed, 21 March 2018 08:27 |
Tilerpep
Messages: 404
Registered: June 2013
Location: Raleigh, NC
Karma: 7
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Senior Member |
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I have the electrolevel 1, only one pump. Thanks guys for confirming pump running is normal even on down request. When i get the pressure side tight, it should limit that as well.
1975 Glenbrook, 1978 Royale rear bath
Raleigh, NC
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| Re: Electro level down switch running pump [message #330206 is a reply to message #330190] |
Wed, 21 March 2018 11:10 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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The pump running is a function of low pressure near the tank. If the key is on and the pressure is low the pump will run. If the key is off the pump will not run. One exception to this is: If the key is on and the pressure is low, but the hold switch is on then the pump will not run. What controls the running is a pressure switch mounted next to the pump, the hold switch, and the ignition switch. The up / down switches are NOT in the pump circuit.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: Electro level down switch running pump [message #330221 is a reply to message #330206] |
Wed, 21 March 2018 20:16 |
dshafer
Messages: 68
Registered: June 2016
Location: SW Ohio
Karma: 3
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I just looked at the schematic and according to http://gmcmotorhome.info/figs/on.gif any one of the three switches can make power available to the relay that sends power to the pressure switch:
1. travel/hold switch in TRAVEL
2. left raise/lower switch in RAISE or LOWER
3. right raise lower switch in RAISE or LOWER
In other words (in a working system with the ignition switch on and system air pressure is low) the pressure switch will turn the compressor ON if you are in TRAVEL or if you are raising OR lowering either side.
1977 26 foot 403
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| Re: Electro level down switch running pump [message #330247 is a reply to message #330190] |
Fri, 23 March 2018 16:03 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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Turn it anyplace from off and it will power the pump through the pressure switch - my E 1 does the same and a look at the wiring indicates this is normal. The E 2 is completely different, only the airbags are the same.
--johnny
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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