RESOLVED ! - T6.1 California - brand new OE fresh water pump runs only for 4 seconds then stops

[Johnny Rocket]

T6.1 California - brand new OE fresh water pump runs only for 4 seconds then stops

Good evening all - here's hoping someone has seen this issue before, and can help !

I recently bought a new dealer-supplied freshwater pump for our California, after flow from the original factory-fit unit became weak - it had gone through phases of shrieking and screeching over the last year (maybe it was compromised because I don't drain my tank, so if it freezes maybe that hurt the pump), so I was convinced it was on the way out. Recently it quietened down, but the flow is still pathetic !

I fitted the new pump, and for a few seconds was very pleased, as the flowrate was much improved - but the pump then stopped after 4 seconds !

Whichever switch I operate - galley sink or my OE-facsimile retrofit rear bulkhead shower switch, the same is true - 4 seconds of good flow, then stop. After a 20-30s wait all is good again, but all you get again is 4 seconds.

I removed the pump and wired it in parallel with the old one to a spare 12V battery, and proved both that the new pump was healthy, and the old one feeble, and that when supplied directly from a dedicated 12V source both pumps run continuously and without issue.

I'm supposing there must be some kind of thermal or other cut-out which is triggering the new pump to quit, and whilst it seems unlikely that the replacement is defective, given that it does run fine standalone, then I guess it could be faulty ?

Has anyone seen this before, and know what the fix is ?

Thanks as always ! John.


STOP PRESS

OK, so before I hit send, I had a think and decided to do a couple more logical and obvious tests:

1) I wired the original pump back into the vehicle, and it too then cut after 4 seconds, so the issue is definitely vehicle-side, and would seem to have been provoked by me disturbing things

2) I took both pumps back into the garage and powered them separately from the 12V spare battery - both run OK and continuously (ABA test !)

3) I connected each pump in turn back to the vehicle loom, and I now get only a single 4 second burst, with now apparently no subsequent recovery by waiting

4) both of the orange 5A fuses under the passenger seat are fine; I swapped their positions, just for the hell of it - no change.


Stumped of Horsell ! ! !

 

[Roger Boeken]

is the water level sensor working correct and shows tank is full ?
pump will stop if running dry or blocked somehow , there is no fuse for the pump it is indeed current drawn by pump that must be within 'normal' limits . It will reset itself after some time.
Perhaps there is a blockage between the pump and the water tap.?
Check the water tap, remove the aerator and try again.

Maybe it is time to descale de tubings and tap ?

 

[Johnny Rocket]

Yes, the level sensor is working entirely correctly.

The pipes are all blockage-free - or at least they must be, as witnessed by the full flow of water, whether from the shower outlet or the sink, during the 4 seconds that the pump will actually stay on !

And the rose in the outlet of the sink tap is completely clear.

I guess there has to be something wrong electrically - I'll try in the morning attaching another consumer to the water pump harness - say a simple light bulb of equivalent power - and see whether that suffers the same cut out after a few seconds . . . .

Thanks.

 

[Johnny Rocket]

OK, I've just done a test with an H7 headlight bulb, and it lights up and crucially stays lit.

When I retry with the pump, it spins and stops as before, but I now get a 'bong' (maybe I did before ?) from the overhead panel which says "Pump protection is active - please add fresh water".

Since the original issue, and to save going fishing every time and flooding the interior of the van, I have been doing all my tests on the unsubmerged pump . . . but now, on a Google search I find:

'The "Pump protection active. Please add fresh water" warning on a Volkswagen California T6.1 is usually caused by an airlock in the water system or a dry water pump after refilling. The control panel senses a drop in resistance or power consumption and shuts the pump down to prevent burnout.'

So maybe the vehicle was all along just trying to protect against what it sensed was an 'airlocked' system.

I'll reconnect the pump, but submerged again, in the tank tomorrow and see if I can make progress.

At least any of you technical night owls have had a jolly good laugh at my expense . . . duurrr ! ! !

As you were . . .

 

[vbk1975]

OK, I've just done a test with an H7 headlight bulb, and it lights up and crucially stays lit.

When I retry with the pump, it spins and stops as before, but I now get a 'bong' (maybe I did before ?) from the overhead panel which says "Pump protection is active - please add fresh water".

Since the original issue, and to save going fishing every time and flooding the interior of the van, I have been doing all my tests on the unsubmerged pump . . . but now, on a Google search I find:

'The "Pump protection active. Please add fresh water" warning on a Volkswagen California T6.1 is usually caused by an airlock in the water system or a dry water pump after refilling. The control panel senses a drop in resistance or power consumption and shuts the pump down to prevent burnout.'

So maybe the vehicle was all along just trying to protect against what it sensed was an 'airlocked' system.

I'll reconnect the pump, but submerged again, in the tank tomorrow and see if I can make progress.

At least any of you technical night owls have had a jolly good laugh at my expense . . . duurrr ! ! !

As you were . . .

@Johnny Rocket, just to confirm that i think you conclusion is correct and a bit of rationale.

The Pump output will be on a MosFET or FET, basically an electronic switch that acts like a relay and fuse in one and control via the Processor in the ECU.

The FET devices vary as how they measure current and protect the output, but given the ECU used for the camper functions on a T6.1, is the VW special vehicle ECU as has been designed to be really flexible, my view is that the current is measured and feed into the processor, to allow the current diagnostics levels to be set in software.
{Some of these device the protection is all done within the FET, you just select a Profile, not the case here IMHO}

They will have an upper threshold "Over current or Short circuit" that will switch off the FET instantly, if you like this is "Fuse" function. Resetting it will likely be an ign cycle or an extended time out (not 30 secs) - some companies will disable an output after X resets and require a diagnostics reset, because there is a hard fault. {You can sometimes see this when people retrofit Xenon lights to a car and they flash a few times before starting}

"Open circuit" protection ie little to no current flowing will normally just result in a fault code being store and perhaps a message if the function is critical, but the output remains on.

I suspect VW have programmed in a intermediate threshold that is a pump running but not enough current being sensed for it to be pumping water. And to protect the pump they have the 4 secs on and then wait 30 secs.

 

[Roger Boeken]

Maybe try pump in place with tubing to sink disconnected so air can easely escape .
It seems that the ECU is overprotective.

 

[Johnny Rocket]

Maybe try pump in place with tubing to sink disconnected so air can easely escape .
It seems that the ECU is overprotective.

Good morning all.

So, the simple expedient of refitting the new pump submerged, and giving it successive short bursts of only a couple of seconds or so, alternately at the sink tap and the shower head, until the lines were purged, was all that was needed - everything is now as it should be, but with a rather better flow rate.

Thanks to the two contributors above for the overnight sanity checks of my thinking - it does seem that the 'Wolfsburg Nanny State', or should that be the MosFET State (!) is alive and well, and strikes again . . . although in this case with pretty reasonable justification I have to say . . . !

I did think, after my embarrassment at the schoolboy misunderstanding of what was going on, I should now delete the thread in shame . . . but I guess I'll maybe leave it to stand, in case someone else at some point ends up scratching their head with the very same issue . . . ? ! ?

Have a good weekend all; JS.

PS see above photo of old (L) vs. new (R) pumps on test before finally fitting the new unit !

 

[vbk1975]

View attachment 153164

Good morning all.

So, the simple expedient of refitting the new pump submerged, and giving it successive short bursts of only a couple of seconds or so, alternately at the ink tap and the shower head, until the lines were purged, was all that was needed - everything is now as it should be, but with a rather better flow rate.

Thanks to the two contributors above for the sanity checks overnight of my thinking - it does seem that the 'Wolfsburg Nanny State', or should that be the MosFET State (!) is alive and well, and strikes again . . . although in this case with pretty reasonable justification I have to say . . . !

I did think, after my embarrassment at the schoolboy misunderstanding of what was going on, I should now delete the thread in shame . . . but I guess I'll maybe leave it to stand, in case someone else at some point ends up scratching their head with the very same issue . . . ? ! ?

Have a good weekend all; JS.

PS see above photo of old (L) vs. new (R) pumps on test before finally fitting the new unit !

Well done,

I don't think it is a school boy error at all, most people would look to test the pump before reassembling the tank lid and filling it and I am sure most T5/T6 guides and threads on the forum will suggest testing before fitting. The bit i find interesting is that VW either felt the need to stop the pump running dry for more than 4 secs or someone thought they could do it so why not. Yet the comet pumps are rated for 30 min dry running, clearly I wouldn't do that, but 4 secs!

 

[Johnny Rocket]

Yeah, I'm hardly a hooligan, and certainly not at all mechanically unsympathetic, but I didn't think just 4 secs of dry running was a particularly arduous or risky operating condition for a pump which, as you say, can evidently survive far worse . . . you live and learn !