Water management in the GC

[Bart7974]

As I already wrote in one of my former posts
we have ordered our GC but it has not yet arrived.

In the meantime I have continued my research on the GC water system for a better understanding.

The information below is from a German VW forum and VW documentation and could be inaccurate or incomplete. You never know.

The water management in the GC does not consist of a directly controlled water pump with simple on-off switches.
It is a microprocessor controlled system: the customer-specific functional control unit (CFCU)

The CFCU has two sense inputs to control water requests .
Input 1) and input 2), these control 4 request signals
1)-Water tap kitchen- or -the shower tap-
2)-Toilet water- or -shower outdoor-

The water pump is activated
When:
1) is active, i.e. water requested
And
Enough water in the water tank
And
Crafter motor not running
And
Greywater tank not 100% filled.
Or
When
2) is active , i.e. water requested
And
Enough water in the water tank
And
Crafter motor not running
(Greywater tank level not relevant here, because water flows into the toilet tank or outdoors.)


When hot water is requested
then :
- the water pump is activated
- hot water circuit opens at the hot water tap
- cold water from the water tank flows into the Truma boiler and the boiler output
flows through the selected water tap.

Bart

 

[Bobcat01]

Great explanation Bart, thank you, I wasn’t aware of the engine running piece.

 

[Bart7974]

that with the engine running is not 100% sure. The board member who wrote this hasn't verified it.
So it is not known if it is "engine running "or "car driving " or not at all

 

[Bart7974]

that with the engine running is not 100% sure. The board member who wrote this hasn't verified it.
So it is not known if it is "engine running "or "car driving " or not at all

maybe one member with a GC can verify this:
-start the engine and open the water tap
and now one level higher
-start the engine , drive and open the water tap

 

[Bobcat01]

Morning Bart, I can confirm the taps work perfectly when the engine is running. I didn’t try it while driving but strongly suspect it will be the same.

 

[Bart7974]

Hi,
o.k thank you for the information

 

[Bart7974]

Morning Bart, I can confirm the taps work perfectly when the engine is running. I didn’t try it while driving but strongly suspect it will be the same.

and now for the next experiment : while driving open the tap

 

[Bobcat01]

Hi Bart, I can confirm everything works while driving including the toilet flush. Thanks to the tester my wife!

 

[Bart7974]

Ha ha , super .
Thank you and your wife for the positive test results.
"Going to the loo" while driving , could save time

 

[Bart7974]

Ha ha , super .
Thank you and your wife for the positive test results.
"Going to the loo" while driving , could save time

or useful in a traffic jam

 

[andyinluton]

Hi Bart, I can confirm everything works while driving including the toilet flush. Thanks to the tester my wife!

Did that with the old motorhome, one of the kids couldn't wait & dived into the loo whilst I checked in at a campsite, I jumped back into van & drove over a speedhump, took about a week for the blue to fade off his backside. He was not impressed.

 

[Tstranne]

Good summary of how it all work! My pump only gets power for a few seconds after open any of the taps!? Any idea what that can be? Control unit failure?

 

[GordonH]

What is the battery status in % and v?

 

[Tstranne]

Battery status checked and 100% ok, same problem off grid as with 220V connected

 

[GordonH]

Can you hear the pump running but no water or does the pump stop running ?

 

[Tstranne]

The pump stops running after these few seconds and power is disconnected. It doesn’t matter which tap I use, the problems is not dependant on which tap

 

[GordonH]

The system will stop the pump in low fresh water or low battery or full waste tank. Does the panel show all OK with fresh and waste water? Try reset the panel (red switch in utility cupboard). If the problem persists try the blue plug reset (switch off red switch in utility cupboard, under dash on left side of van you will see the KFG unit which has 3 connectors one of which is blue, unplug the blue connector, wait 30s and then plug back in and switch red switch back on)

 

[Tstranne]

Thx for your feedback, but I hace ticked all thise boxes already. Water levels checked snd ok. Have resetted several times, both the red button only, then the blue connector, then all 4 connectors (incl the blue) on the KFG, but nothing helps. I do have replaced the pump half a year ago to a stronger one (as many here in the community have done) it has worked perfectly until now. I read somewhere (cant find it again) that there might be some kind of overload function in the KFG that might be activated, do you know anything about that?

 

[Tstranne]

Just made an interesting observation: when I disconnect the connector to the pump, the power remains on and don’t get disconnected. When I connect the connector to the pump, the power disconnects after a couple of seconds! I have to buy a new pump to test, most probably it’s the pump that somehow indicates to the KFG to cut the power!?

 

[GordonH]

I believe you are correct. There is an overload sensor of some type in the KFG. I don’t know the details but like you I have read about it on other forums.

 

[mattandlisagbr]

Just made an interesting observation: when I disconnect the connector to the pump, the power remains on and don’t get disconnected. When I connect the connector to the pump, the power disconnects after a couple of seconds! I have to buy a new pump to test, most probably it’s the pump that somehow indicates to the KFG to cut the power!?

I have the same problem ! Put the original pump back in and all works OK. Coincidentally I had drained the system beforehand and fitted a new tap …but can’t workout why the stronger pump worked fine and now fails. Note that it works if held out of the water - but the system cuts out as soon as it’s dropped into water - even with the black pipe disconnected.

 

[GordonH]

I have the same problem ! Put the original pump back in and all works OK. Coincidentally I had drained the system beforehand and fitted a new tap …but can’t workout why the stronger pump worked fine and now fails. Note that it works if held out of the water - but the system cuts out as soon as it’s dropped into water - even with the black pipe disconnected.

Could be that when you put it in the water it is then pumping water so will draw a higher current than when running ‘dry’.

 

[secret lemonade drinker]

The power supply to the pump is a current limiting type, the higher flow rate pump will draw more current when operating, tripping the limit on the power supply. The T6.1 works the same way, you probably need a pump with a flow rate of no more than 10 litres per minute.

 

[mattandlisagbr]

I get that there is a limit on current draw and that drawing water will likely increase the power demand - but this doesn’t explain why it originally worked. This is happening to quite a few folk - some having quite happily worked for a year or so

 

[GordonH]

The power supply to the pump is a current limiting type, the higher flow rate pump will draw more current when operating, tripping the limit on the power supply. The T6.1 works the same way, you probably need a pump with a flow rate of no more than 10 litres per minute.

GC factory fit pump is 19l/min