Bought a 1986 390 Express last November, it is a 2 hour drive away so a pain to get ready for the water. The only thing I can't figure out is that the Vacu Flush pump works and creates good suction but it won't shut off unless you use the breaker. Normally I would say the vacuum switch is bad but I can't locate the switch or the vacuum tank it's supposed to be mounted on. This is the type of Vacu Flush that has the old type diaphram pump mounted separate from the vacuum tank. Does anyone know where the vacuum tank and or vacuum switch is hidden in this boat?
Sea Ray 390 Vacu Flush Puzzle
- Thread starter CRay
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- Joined
- Mar 5, 2001
- RO Number
- 3655
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- 1,800
The vacuum switch is mounted in the end of the vacuum tank, but where the vacuum pump and tank located are on your boat, I have no idea.
While the pump is running, instead of shutting it off, try following it's sound and see if you can't locate it that way (it won't hurt the pump any if it runs for 15 or 20 minutes while you're searching for it). The vacuum tank will usually be right next to the pump.
It could be either the vacuum switch or the (4) duckbill valves in the vacuum pump - failure of either will cause the pump to run on and on. I'd first try replacing the duckbills in the vacuum pump. It's easier and cheaper to do that first. The vacuum switch is more expensive, and not the easiest thing in the world to change.
While the pump is running, instead of shutting it off, try following it's sound and see if you can't locate it that way (it won't hurt the pump any if it runs for 15 or 20 minutes while you're searching for it). The vacuum tank will usually be right next to the pump.
It could be either the vacuum switch or the (4) duckbill valves in the vacuum pump - failure of either will cause the pump to run on and on. I'd first try replacing the duckbills in the vacuum pump. It's easier and cheaper to do that first. The vacuum switch is more expensive, and not the easiest thing in the world to change.
No problem locating the pump. It is the old S series type. In fact there is a second one that functions as an overboard discharge. Both pumps run and the one for the head generates really strong vacuum and it flushes really well. The system shows signs of previous modifications and I wonder if someone removed the vacuum tank altogether so therefore no tank and no switch. Boat will be home late next week and will have others familiar with the system take a look.
- Joined
- Mar 5, 2001
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- 3655
- Messages
- 1,800
I suppose that's a possibility, although not a very good way to do it. It "could" get expensive, trying to restore it to correct operation.
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- Sep 16, 2003
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The tank is cylindrical and installed between the head and the vac pump, usually closer to the head
I cant imagine anyone removing the tank...
Once you find the tank, the switch is at one end. Push the rod in, it will turn off the pump. If the pump stays off I d suspect there is enough vacuum but the switch is bad. If it comes back on when you release the switch, then there isn't enough vacuum
The switch itself rarely goes bad it s usually the diaphragm and rod but you have to get the whole thing, about $120
Last possibility someone tried to adjust the switch. Some are adjustable others are not
I cant imagine anyone removing the tank...
Once you find the tank, the switch is at one end. Push the rod in, it will turn off the pump. If the pump stays off I d suspect there is enough vacuum but the switch is bad. If it comes back on when you release the switch, then there isn't enough vacuum
The switch itself rarely goes bad it s usually the diaphragm and rod but you have to get the whole thing, about $120
Last possibility someone tried to adjust the switch. Some are adjustable others are not
Capt. Bill1
Active member
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- Jan 1, 2000
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- 2017
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- 6,127
The tank is not small. So just follow the sani hose back from the head to the pump. If you can't find the tank, then some one either removed it or never installed it. Stranger things have happened.
Thanks Pascal for the tech advice. After the head the hose out through the bulkhead and behind the dinette about 8 ft or so. Maybe the vac tank is buried but I'll dig into it when the boat gets back home. At least the system is "usable" until I get to the bottom of it. Maybe Sea Ray installed a secret door or something.
I think I found out where the VT is located. Sea Ray's web site has old parts diagrams and shows the VT located under the dinette behind the AC unit. Sounds like a PITA to get to. Hope there is a panel that comes off to get at it. Will advise in about 2 weeks what I find. Thanks again.