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Old 07-03-2012, 11:40 PM   #1
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1979 28' Ambassador
California , California
Join Date: Jul 2012
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Troubleshooting water pump

I have a 1979 Ambassador that is 95% original with all systems operational. Just recently we have been having an issue with our water pump. It is a PAR 36950-2000. After running water through all of our fixtures, the water pump will run intermittently. Every 10-12 seconds. Water will run out of the pressure relief valve whenever it cycles on. It also blows the 6 1/4 amp fuse after a minute or so. I spoke with a friend who was an RV maintenance tech for over 20 years and he suggested removing the pressure control unit on the front of the pump, flush the line and check to see if there is debris in the pinhole orifice on the disk that inflates and trips the pump off. I followed his advice and still have the same issue. The disk, which appears to be made of latex is not smooth. It is wrinkled but still inflates for the most part.

Any suggestions?
Thank you in advance.

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Old 07-04-2012, 12:11 AM   #2
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1971 25' Tradewind
Menlo Park , California
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Well, the fuse blowing indicates a overcurrent situation, which would tend to suggest the pressure switch is faulty. You could make sure by attaching a pressure gage somewhere in the system, which is not a bad plan in any case. Once you know it's the switch, you can either replace it or dissemble and attempt to reduce the strength of the spring so as to reduce the pressure at which it turns off....

- Bart

Bart Smaalders
Menlo Park, CA
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Old 07-04-2012, 12:18 AM   #3
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1978 28' Ambassador
Morada , California
Join Date: Jan 2006
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" Water will run out of the pressure relief valve whenever it cycles on"

Are you referring to the valve near the outside water inlet connection? Or, ??? whatever valve you're referring to, if water is being emitted, there is a problem in that area, it would seem...

I replaced the original water pump in our 78 Ambassador with a current model variable flow model that is far superior to the old unit.

This new pump matches the flow required by the valve being opened - cracking a faucet a small amount results in a quiet, low speed from the pump - opening both the bath & kitchen faucets causes to pump to speed up to match the need - works great!

BTW - I had very low flow from the HOT side of the kitchen faucet when we bought our AS a few years back... I cut the copper tubing near the faucet on the HOT side and found some small 'balls' of hard crud (probably from water heater that wasn't flushed annually) lodged inside... I took the faucet cartridge and tried to 'blow' the crud out with an air hose without success... Ended up replacing the entire faucet with a new Moen similar unit - Ahhhh, mucho hot water for the dishes now!
Ray & Pat; Morada, CA
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Old 07-04-2012, 02:34 PM   #4
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1979 28' Ambassador
California , California
Join Date: Jul 2012
Posts: 2
My airstream is a rear full bath. The pump is located in the bottom of the bathroom vanity in front of the water heater. The pump is variable speed and belt driven.

The valve I am referring to is a pressure relief valve next to the "city" water pressure regulator. (see pic 1)

This valve is intended to send over pressure out of the system and uses the cold water winterizing spigot to protect the interior systems.

The diaphragm that I was referring to earlier that inflates at 40 psi (supposedly) and triggers the switch to <OFF> seems like my best guess for the switch malfunction and the over-current

Attachment 162334

Attachment 162335

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