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Old 23-05-2022, 07:42   #1
TCL
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Pump needs light tap

My Jabsco Par-Max water pump for the freshwater system recently began requiring a light tap to kick on -- by which I mean just like a tap with my knuckles. Trying to think of the cause -- whether mechanical or electrical -- before attempting any servicing. Any insight would be appreciated.
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Old 23-05-2022, 07:54   #2
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Re: Pump needs light tap

Bearings are worn.

Armature is polling out against the field preventing the motor turning from rest.

Once the motor is spinning the armature floats on the magnetic field.

Worn bearings and worn seals seem to go together so expect some corrosion when you remove the pump and open the motor.

If service is successful celebrate by purchasing a new pump.
A spare will come in handy.
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Old 23-05-2022, 08:10   #3
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Re: Pump needs light tap

Do you have a fine-mesh strainer on the inlet side, (factory recommended)?
Or, the switch itself can have one or more internal issues.
None of the little built-in switches on the popular pumps are of robust design, and are to be considered as a "remove and replace" item.
It's an easily changed part of not great expense.
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Old 23-05-2022, 08:24   #4
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Re: Pump needs light tap

Check the easy things first, like the switch, bypass it to check operation, no tools required.
A parts breakdown will show that there is not a seal for the motor shaft, the "guts" of the motor are completely isolated on the other side of a diaphragm together with the eccentric drive.
If the diaphragm has a leak, you will see water coming out of the motor housing, and the problem is self-identifying.
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Old 23-05-2022, 09:18   #5
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Re: Pump needs light tap

motor is going bad
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Old 23-05-2022, 16:28   #6
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Re: Pump needs light tap

The pump has a small micro switch in the front. It's designed for 250v, not 12v. But it's cheap and the contacts will either stick together or fail to make contact because pitting from a too high amp flow. Sometimes overcome by tapping the motor.

Switch looks similar to this. You can buy them on ebay or Amazon. About $2-3.
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Old 24-05-2022, 06:48   #7
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Re: Pump needs light tap

It is most likely the brushes in the motor. Tapping it allows the brush to touch the commutator and that is why it starts again. But your brushes are failing, and need to be replaced. Or toss it and buy a new one before the bearings also fail.
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Old 24-05-2022, 06:59   #8
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Re: Pump needs light tap

My freshwater pump also occasionally needed a tap to get going. I think it's the pressure switch. Problem has been much less frequent after I rebuilt the pump head. I carry a spare pump but haven't needed it in the 4 years since I first saw the problem.
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Old 24-05-2022, 09:35   #9
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Re: Pump needs light tap

Quote:
Originally Posted by Lepke View Post
The pump has a small micro switch in the front. It's designed for 250v, not 12v. But it's cheap and the contacts will either stick together or fail to make contact because pitting from a too high amp flow. Sometimes overcome by tapping the motor.

Switch looks similar to this. You can buy them on ebay or Amazon. About $2-3.
Don't just replace the switch. Use the switch to power a relay that powers the motor. These switches are not sufficient to handle motor starting loads. 40 amp automotive relays can be had for a few bucks and can be fit into a socket. I did this on all of my pumps years ago and have never had to replace a pump switch since. I have replaced a couple of relays over the years. Since I use the same relay for several different pumps I only need to carry one type of spare. These relays and sockets are available from multiple on-line sources and in a pinch from any autoparts store.
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Old 24-05-2022, 17:22   #10
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Re: Pump needs light tap

Quote:
Originally Posted by TCL View Post
My Jabsco Par-Max water pump for the freshwater system recently began requiring a light tap to kick on -- by which I mean just like a tap with my knuckles. Trying to think of the cause -- whether mechanical or electrical -- before attempting any servicing. Any insight would be appreciated.
Pressure switch, bearings don't cause intermittent running, if It has an adjustment try adjusting the pressure up or down, the set point is probably worn.
In that case just replace the switch.
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Old 24-05-2022, 17:24   #11
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Re: Pump needs light tap

Quote:
Originally Posted by stormalong View Post
Don't just replace the switch. Use the switch to power a relay that powers the motor. These switches are not sufficient to handle motor starting loads. 40 amp automotive relays can be had for a few bucks and can be fit into a socket. I did this on all of my pumps years ago and have never had to replace a pump switch since. I have replaced a couple of relays over the years. Since I use the same relay for several different pumps I only need to carry one type of spare. These relays and sockets are available from multiple on-line sources and in a pinch from any autoparts store.
Makes perfect sense!
Good tip.
Thanks Stormalong!
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Old 24-05-2022, 18:12   #12
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Re: Pump needs light tap

Quote:
Originally Posted by sailing_gal View Post
It is most likely the brushes in the motor. Tapping it allows the brush to touch the commutator and that is why it starts again. But your brushes are failing, and need to be replaced. Or toss it and buy a new one before the bearings also fail.
Second for the brushes,,,,trying shootin some WD 40 into the armature, might get another year out of it
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Old 24-05-2022, 18:54   #13
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Re: Pump needs light tap

Using those "cube" Bosch relays is a good idea, or alternately, (for water pressure,) a Square D/Furnas external switch makes a good choice also, with the added benefit of user adjustable cut-in/cut-out settings.
My Furnas switch just failed a few months ago after 28 years of 24/7/365 use.
It would actually still work if I gave it a rap but went ahead and replaced it.
The motors on the popular pumps, Jabsco/Shurflo/Flojet, are basically just an automotive windshield wiper motor.
My water pump is original to the boat, it's a US made Flojet, ~3.5gal a minute, needed a diaphragm/valve kit at ~25 years, fixed it, still runs great, motor is quiet.
Ran a few #s for fun, almost rocket science math.
Here in the PNW, for a person doing an hour or so of commuting each day for work and some driving on the weekend, it could be more-or-less normal for ~4 months a year to be using the wipers, say ~3>4 hours a week, (could easily be a lot more).
For a 10-year-old car that works out to be ~480>640 hrs. of motor run, (again, could be much more).
On my boat I use ~3gal. per day of water, the Flojet pump runs a total of ~1 min. per day. After 28 years that's ~170hrs run time.
Many vehicles up here are likely to have windshield wiper motors than probably have well over a thousand hours of run time.
My pump is at 28 years, even at the outside that's only maybe 200hrs time.
When's the last time your windshield wiper motor had a dragging armature, bad brushes, or bad bearings.
I would posit that most people have never had a wiper motor fail in a vehicle.
Pumps/pump parts can break down, the switches ALWAYS fail, the basic motors, not so much.
All bets are off if your water pump is in a wet/salty bilge area.
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Old 24-05-2022, 21:40   #14
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Re: Pump needs light tap

I had a Vetus pump that acted up a few weeks after install. It would sometimes stutter before switching off. More often than not it needed a light to to start.

I assumed it was the pressure switch and asked the supplier to send me a replacement switch rather than replace the whole pump. But they elected to send a replacement pump (warranty). The replacement has beed flawless in operation.
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