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Earth shunt reassurance needed

Zen Dog

Zen Dog

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Messages
4
Location
Lyme Regis
Vehicle
T5 SE 174
Hi all, I know it's a bit of an old chestnut. My leisure batteries finally expired. No problem with that, they were at least 10 years old. However, while I was in there I checked the resistance from the negative lead which goes from the rear battery to the shunt and a known good earth on the body, getting a reading of about 500 ohms. As the earth shunt resistance is 0.2 ohms it confirmed in my eyes that the shunt to body earth has failed. No surprise, it's a known and well documented fault.
On removing the front battery I noticed an earth lead from the negative terminal to a bolt on the seat base. It was very professionally done, so much so that I took it to be an original part of the wiring.
But then I got to thinking; an unusual occurrence. Surely a second earth in the system would effectively short out the earth shunt? So my questions are:
Am I correct in thinking that the earth to the front seat is a workaround done by a previous owner after the earth shunt failed, or does everyone have one?
Second question, does the earth shunt reading just affect the display on the camping unit or does it also affect the charging rate from either the charger unit or the engine?
If it helps anyone, I found it easy to remove the front battery by undoing the star bolts at the back of the seat runners and slackening off the nuts at the front of the runners. The seat can then be pivoted forwards to give plenty of clearance.
In a similar vein, to access the earth shunt I cut an access panel from the battery bay. There is about 6 inches clearance on the fridge side for the hacksaw/jigsaw blade. I then drilled an earth point behind the battery and ran the new earth to that, which will let me check it easily in future.
Plan A was to replace the hatch, but I was disturbed by the lack of cooling to the fridge heat exchanger and charger unit, so I will leave the hatch open and maybe drill a couple of vent holes up to the wardrobe. This might even give the wardrobe some mildly heated air.
 
WelshGas

WelshGas

Retired after 42 yrs and enjoying Life.
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T5 SE 180 4Motion
Hi all, I know it's a bit of an old chestnut. My leisure batteries finally expired. No problem with that, they were at least 10 years old. However, while I was in there I checked the resistance from the negative lead which goes from the rear battery to the shunt and a known good earth on the body, getting a reading of about 500 ohms. As the earth shunt resistance is 0.2 ohms it confirmed in my eyes that the shunt to body earth has failed. No surprise, it's a known and well documented fault.
On removing the front battery I noticed an earth lead from the negative terminal to a bolt on the seat base. It was very professionally done, so much so that I took it to be an original part of the wiring.
But then I got to thinking; an unusual occurrence. Surely a second earth in the system would effectively short out the earth shunt? So my questions are:
Am I correct in thinking that the earth to the front seat is a workaround done by a previous owner after the earth shunt failed, or does everyone have one?
Second question, does the earth shunt reading just affect the display on the camping unit or does it also affect the charging rate from either the charger unit or the engine?
If it helps anyone, I found it easy to remove the front battery by undoing the star bolts at the back of the seat runners and slackening off the nuts at the front of the runners. The seat can then be pivoted forwards to give plenty of clearance.
In a similar vein, to access the earth shunt I cut an access panel from the battery bay. There is about 6 inches clearance on the fridge side for the hacksaw/jigsaw blade. I then drilled an earth point behind the battery and ran the new earth to that, which will let me check it easily in future.
Plan A was to replace the hatch, but I was disturbed by the lack of cooling to the fridge heat exchanger and charger unit, so I will leave the hatch open and maybe drill a couple of vent holes up to the wardrobe. This might even give the wardrobe some mildly heated air.
This might help. The Camping side electrics.
I don't think the extra Earthing point will matter, but I'm not an electrician Automotive or otherwise.

Screenshot 2019-09-27 at 12.53.23.jpg
 
Zen Dog

Zen Dog

VIP Member
Messages
4
Location
Lyme Regis
Vehicle
T5 SE 174
Thanks for that Welshgas, I've downloaded the training manual but to me the wiring diagrams are as clear as mud. The other one, I think it's the functional wiring diagram is even worse!
 
bvddobb

bvddobb

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Messages
1,332
Location
Netherlands
Vehicle
T5 SE 174 4Motion
You are correct, that extra earth cable will render the shunt useless.
Indeed. It doesn’t short circuit the shunt, but bridges it. Systems will still get power, but the CU won’t get correct battery info. There is some logic in the CU that uses the shunt info, e.g. to decide when to shut off the fridge or the parking heater because of too low battery capacity. That will no longer work correctly once the shunt is bridged. There may be other erratic behaviour of the leisure circuit (flickering lights when the parking heater kicks in).
Best is to make sure the shunt is well connected to earth and then disconnect the bridges. There is a DIY kit available on the german Caliboard shop to improve the shunt earth. We have installed it and all our leisure circuit issues have gone!
 
Tom Rae

Tom Rae

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Messages
355
Location
Edinburgh
Vehicle
T6 Cali On Order
Indeed. It doesn’t short circuit the shunt, but bridges it. Systems will still get power, but the CU won’t get correct battery info. There is some logic in the CU that uses the shunt info, e.g. to decide when to shut off the fridge or the parking heater because of too low battery capacity. That will no longer work correctly once the shunt is bridged. There may be other erratic behaviour of the leisure circuit (flickering lights when the parking heater kicks in).
Best is to make sure the shunt is well connected to earth and then disconnect the bridges. There is a DIY kit available on the german Caliboard shop to improve the shunt earth. We have installed it and all our leisure circuit issues have gone!
I used the DIY kit on my T5, not difficult and sorted it with no compromises.
 
Zen Dog

Zen Dog

VIP Member
Messages
4
Location
Lyme Regis
Vehicle
T5 SE 174
Thanks all, I couldn't see how the shunt could be doing anything. I already have the parts to earth the shunt properly, so on with the game......
 
J

JohnVZ

Messages
29
Location
London
Vehicle
T5 Cali on order
I used the DIY kit on my T5, not difficult and sorted it with no compromises.

Hi - would someone be able to point me to a Uk version of the Earth shunt kit?
Thanks in advance!
John


Sent from my iPhone using Tapatalk
 
sidepod

sidepod

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T4 PopTop
Am I missing something?

The OP says he has additional earth strap from second battery as per this in red.
There is already one shown in blue. How does the extra earth affect the shunt?
06A2AECB-C874-4AF5-9BFE-6133B012BCD4.jpeg
 
sidepod

sidepod

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The dodgy link is this one.
90064902-9992-409A-8ADE-D1ECE1F807DC.jpeg
 
Loz

Loz

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Berkeley Gloucestershire
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T6 Ocean 204 4Motion
Those drawings are not correct they are concept drawings. The shunt is actually on the blue leg you indicated on the first picture.
The shunt kit only reinforces the bad bond between the chassis side of the shunt and a better chassis point.
 
sidepod

sidepod

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That makes more sense :thumb
 
sidepod

sidepod

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This reminds me, I should get around to fixing my sisters shunt issue on her Cali.
 
zeratul

zeratul

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T5 Beach 4Motion
Hi everyone
I think my heater might be suffering from the earth shunt problem. Auto-turns itself off when on battery, even though it's full, works when plugged in or engine running.
But I have a VW T5 Beach (yes, a beach with parking heater).
Where is the earth shunt located on a California Beach?
 
WelshGas

WelshGas

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Hi everyone
I think my heater might be suffering from the earth shunt problem. Auto-turns itself off when on battery, even though it's full, works when plugged in or engine running.
But I have a VW T5 Beach (yes, a beach with parking heater).
Where is the earth shunt located on a California Beach?
I don't think there is one as the 1 Leisure Battery isn't monitored as it is on the SE/Ocean which has the Control Panel and 2 Leisure Batteries.

How old is the Leisure Battery?
What voltage are you measuring when " Full "?
What voltage are you measuring when the Parking Heater stops?

The Parking Heater stops working if the voltage drops to 11.5v, or fuel level in the fuel tank drops below 25% or so.
 
Loz

Loz

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Even though you don’t have a shunt, you might still have a poor connection. Start with the battery terminals.
 
B J G

B J G

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Stamford
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Are you sure that you have an independent heater? Caravelle and I think Beach had the option to run heat by using the engine heater for a short period after engine switched off, 20 minutes?
 
zeratul

zeratul

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632
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T5 Beach 4Motion
I don't think there is one as the 1 Leisure Battery isn't monitored as it is on the SE/Ocean which has the Control Panel and 2 Leisure Batteries.

How old is the Leisure Battery?
What voltage are you measuring when " Full "?
What voltage are you measuring when the Parking Heater stops?

The Parking Heater stops working if the voltage drops to 11.5v, or fuel level in the fuel tank drops below 25% or so.
Battery is 6years old
Voltage : 12.2v - not 100% sure if that's full, I've plugged it on hookup and will check again in a couple of hours.
It's never been replaced. Recently the engine battery got replaced.

I will let you know after the hookup what the values are: idle full battery and when the heater gives up (the fans never start). Will test that tonight.
Thanks for any help!
 
zeratul

zeratul

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T5 Beach 4Motion
Are you sure that you have an independent heater? Caravelle and I think Beach had the option to run heat by using the engine heater for a short period after engine switched off, 20 minutes?
Yes. I've used it before. It used to run all night. It was an option 1700euro at the time, at least on our Belgian option list. I also know and have the excess heat feature, it's different.
 
WelshGas

WelshGas

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Battery is 6years old
Voltage : 12.2v - not 100% sure if that's full, I've plugged it on hookup and will check again in a couple of hours.
It's never been replaced. Recently the engine battery got replaced.

I will let you know after the hookup what the values are: idle full battery and when the heater gives up (the fans never start). Will test that tonight.
Thanks for any help!
12.2v is nowhere near full.

The Diesel Parking Heater takes a lot of amps to start up, so could well be dragging the voltage down to 11.5 v at which point the Parking Heater will switch off to protect the leisure battery.


38860F82-810E-4065-ACBD-C020DA7C31FB.jpeg
 
zeratul

zeratul

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T5 Beach 4Motion
I think you are correct. After 8hours on hookup, leisure battery idle was 12.4v
Heater did start fine this time, during start voltage dropped to 11.7-11.8. It didn't turn off.
I also did not have my Waeco fridge on, could make a difference as well.

So I guess a combination of battery wear and non-full battery could be the cause... ?!
 

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