I had exactly this issue a year or so ago. Batteries were the issue. In the end I got both leisure batteries replaced as they were 5/6 yrs old. Never had the issue since.How good are the Leisure Batteries? If original then they are 10 years old and maybe we’ll past their prime.
The Parking Heater will switch Off if:-
1. You have less than a 1/4 tank of fuel.
2. If the Leisure Battery voltage drops to 11.5volts at any time. Check the Control Panel voltage screen when Parking Heater is started.
3. The Parking Heater starts and heats up the vehicle . When it reaches the set temperature it will slow down, fuel pump ticking will slow. If you exceed the set temperature the heater will switch OFF.
Check all the above and try the heater on Level 7.
If the Leisure Batteries voltage drops then probably time to replace them. Will probably work OK if only used when plugged into EHU.
Thought i'd update. Batteries turned out to be knackered. Tried longer charge etc. Batteries appear undated, but i think are originals (2013) marked VW AG.Driving the van or just plugging it in for half an hour will give a false impression, it takes about half an hour after stopping the engine or unplugging for the voltage to stabilise to its true state of charge.
To get from 40 % to full you really need the van plugged in for 24hours to give the batteries a proper charge.
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