Have you checked the earth wire for any corrosion. We had this issue on a car and what had happened was it was going flat so we swapped the battery. Few hours later weird electrical issues so i followed the earth to find it was hanging on by a little bit of metal it looked like a botched job so I had to get a new earth and attach a new ground point. Oh and is it the same battery as before i.e same voltage etc. Have you checked if the battery is keeping a charge or at what ratings it is running at with a multi meter?

 

I haven't checked the earth, not sure where the earth is? It is the same battery as before, it seems to be losing charge over time, I don't know if I've maybe got a parasitic draw somewhere that's causing it to lose charge.. Do you mean what voltage it is at when the van is running?

 

if you follow the cable from the negative terminal on the battery to where it terminates on the chassis of the vehicle somewhere, that could be the problem, they can deteriorate over time as they are just cable attacked by all sorts of weather and salt etc.


check the voltage of the battery at:-


1. Nothing turned on, no key in the ignition ( should see 11.5 - 12.5 VDC) ( anything below 11.5 battery is dead)

2. cranking the engine ( requires a friend) (could Drop to about 10 VDC)

3. Engine running at idle (should be about 13.5 VDC)

4. Engine running at 2500 RPM (should be around 14.5 VDC)

 

sorry for the delay in a response. @Vapulabis explained it perfectly. Good luck in finding the problem.