Shurflo 4029 Water pump won't stop

[1881TB]

I was awoken at about 6am by a humming noise which I first thought was a generator in a nearby van but turned out to be my water pump running for no reason.

It is a Shurflo 4029-181-A32. My van is a 2013 AT Comanche.

I have read previous water pump threads and gone through all the possible causes I could find:

I can't find a significant leak and the fresh tank is full with hot and cold running as normal. It's just that the pump is on all the time. I now have to switch it off at the control panel to stop it.

I have located the screw on the end of the pump which controls the pressure at which the valve should close to stop the pump and adjusted it with an Allen key 3 full turns in both directions to no avail.

I have taken the filter off and emptied the small amount of detritus which was in there.

All the wires seem OK.

Can anyone think of anything else?

 

[M-J]

Could a faulty relay on the tap do this?

Pump thinks the tap is open when it’s not?

 

[Sundowners]

If there is definitely no air In the system----- and no water is being pumped out anywhere------ I think it can only be the pressure switch????????-------- I would have suggested fitting an in line switch but these seem to be quite expensive???? ( Unless you can find a cheap one???)
I think the most practical solution would be a new pump, and keep the old one as a spare---- swap the switch over IF you ever had to use it. ------ these pumps are incredibly reliable in our experience!!!!!
Maybe if you looked inside you switch you might find some rubbish?????
Wait for some more useful suggestions!!!!!!!!
I haven't looked for you pump part No. just assume it's a normal sureflow one!!!!!!!------ it might be something totally different!!!!!!
Edit----- --------if your van has micro switches on the taps------ ignore everything I said!!!!!

 

[The Wino]

Yes I was just going to ask if its a pressure sensing system or a microswitch one but odd there are no leaks

 

[1881TB]

I can't see any pressure switches at the taps, I think the system must be pressurised. I can't work out where the water is going if it is being pumped when the taps are closed. Water flows when taps are opened so it is capable of pumping.

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[M-J]

There’s a video on YouTube showing a crack in the filter housing. Not sure if yours is similar.

 

[hilldweller]

Ours to ages of fiddling before a new pump cured the problem.

They are not that expensive, throw one in.

 

[pappajohn]

Almost certainly the pressure microswitch in the end of the pump.
A replacement switch block is available or you could simply swap the microswitch itself.
I was told by reputable dealer they aren't replaceable... Rubbish.... Takes 10 minutes.

 

[1881TB]

Can they be taken apart fairly easily? I don't want to end up with no pump at all. I'm in France (Brantome) at the moment but heading home.

 

[Diabalo]

I have the same problem which sorts itself out if I give the micro switch a tap, so I guess it's stickining or dirty contacts. The problem is I can't find the correct replacement switch, part No 94-890-00. Did you replaces yours?

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[1881TB]

I have replaced the pump. However, the new pump does the same thing. I have just spent some time on hook up and it is fine so I'm guessing it's an electrical problem, maybe a voltage drop..? I have replaced my leisure batteries and will see if that has fixed it in a few days of non-hooked up camping. There is also a weep from the kitchen tap - it is very slight but it will be the next thing to be replaced until I get to the bottom of the problem.