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Old 08-03-2008, 04:27 PM   #1
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1996 Monaco Dynasty 325 Cummings.

Found a "guizzmo" that is labeled a Vacuum Generator in Monaco's wiring diagram. When the heater controls are turned on (any position) the "Vacuum Generator" starts hissing. I put my finger on a fitting out of the top and there is a large amount of air flowing out. The "Vacuum Generator" has a 1/4" air supply coming into an electric solenoid that allows the air to pass through the it and into the vacuum tank (grapefruit sized tank). All of this is mounted on the front firewall.

My question is how do i get the "Vacuum Generator" to quit hissing and what is the "Vacuum Generator" called.

Any help appreciated...
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Old 08-03-2008, 04:27 PM   #2
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1996 Monaco Dynasty 325 Cummings.

Found a "guizzmo" that is labeled a Vacuum Generator in Monaco's wiring diagram. When the heater controls are turned on (any position) the "Vacuum Generator" starts hissing. I put my finger on a fitting out of the top and there is a large amount of air flowing out. The "Vacuum Generator" has a 1/4" air supply coming into an electric solenoid that allows the air to pass through the it and into the vacuum tank (grapefruit sized tank). All of this is mounted on the front firewall.

My question is how do i get the "Vacuum Generator" to quit hissing and what is the "Vacuum Generator" called.

Any help appreciated...
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Old 08-04-2008, 01:29 AM   #3
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Broke, welcome to iRV2.com. We are glad to have you joun s here and we look forward to reading of your adventures and experiences. Since a diesel pusher will not create enough vacuum to manipulate the dash dampers, an electric vacuum pump (generator) is used. This will alow you to control the airflow to the proper area; defrost will blow onto windshield, heat on the floor, etc. If the air is directed to the right place you are good to go. If not you may have a vacuum line come loose.
I am putting in a shortcut to our New Member Check-In section so others can welcome you to our website. Good luck and stay safe.
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Old 08-04-2008, 04:08 AM   #4
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Broke, welcome. I wonder if you might not have a vacuum leak. Our vacuum pump is mounted in the electrical compartment right below the driver's seat and I can definitely hear it when it comes on. It is, however, a humming type noise that is typical of a motor rather than a hiss.

If you can find some way to plug the line leading away from the vacuum generator temporarily (I have a vacuum gauge with a barb type insert for that sized hose), turn the ignition on and see if the noise stops. What I'm suggesting is a "divide and conquer" between the vacuum generating and the tubing itself regarding your hissing noise. Sometimes, the actual source of a sound can be different than we initially think.

If you do find that the sound is coming from the tubing, there could be a fitting off of one of the valves somewhere. As Mike (RV Wizard) pointed out, the vacuum is used to control the dash vent direction and there are several valves mounted underneath to allow the vacuum to do that.
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Old 08-06-2008, 06:27 PM   #5
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Thanks for the warm welcome and replies.

Im not sure if I was clear on the problem (maby theres not one). Everyting works fine in referance to the dash, defrost and floor heat vents switching back and forth.

The question is, is it normal for air to come out of the top of the "vacuum generator" (enough volume that one can hear it when walking around the outside?

Sorry it took so long to reply as I still have to work.
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Old 08-06-2008, 06:33 PM   #6
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RV Wizard,

Went to the New Member Check-In area and I'm not sure if i need to do anything or not. I want to keep posting and/or post correctly.

Please advise.
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Old 08-06-2008, 10:05 PM   #7
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Broke...Welcome to iRV2!
All is good here on the forum - RV Wizard put a link in the New Member area so others can welcome you and also give you more exposure to your question.

I would also like to invite you to join the Monaco Owners forum... just say yes.... and it will be take care of - all for free!

Just keep posting and visiting the forums often...hopefully we will soon have an answer to your questions...
Again... welcome to the forum...


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Old 08-07-2008, 06:13 AM   #8
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A vacuum pump/generator is virtually the same as a air compressor. Vacuum on one side of the pump and compressed air on the other. It it normal to hear noise and feel air from the vacuum pump when you turn the ignition or engine on until a preset level of vacuum is achieved. The pump may also come on when selecting different modes. The dash air/heater plenum has different vacuum operated baffles to direct the air for different modes: Max AC, AC, floor, top vents, etc.
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Old 08-07-2008, 08:44 AM   #9
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MonacoMama, yes.

Sixpack98 thanks for the reply.

Let me describe the "vacuum generator".

It consists of 2 parts.

The first is an electric solenoid that has a air input (from the coach air system) on one side and an outlet on the other. When the heat/AC is turned on I can hear the solenoid click and start to allow air to pass through it. Seems to work fine.

The other part screws onto the output side of the solenoid and is more-or-less just a diaphragm. It has a small approximately 1/8" ID flexible tubing coming out of the bottom that goes to round grapefruit sized plastic tank. The top has an open (bleed off) port. There is a piece of tubing, with a one-way vacuum valve, going between the bottom port and the bleed off port. On the front of the diaphragm there is an adjustment screw. The whole unit is approximately 4"x4"x4".

I took this apart and could not find any holes or other things that seem broken. It is super clean and in like new condition. Everything seems to work good just the large amount of air coming out of the top of the bleed off port when the system is on.

Any help appreciated.

Craig
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Old 08-08-2008, 01:13 AM   #10
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Craig, it sounds like you have a venturi effect created vacuum. If this is true you will have to allow as much air out as is pushed in or you will loose the vacuum. It sounds as it is working as per design.
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Old 08-08-2008, 09:23 AM   #11
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Why don't you call Monaco and ask them about it?
It's been 5 days since you first posted. If you had called Monaco on the 3rd you would probably have the answer to your question.
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