I think I’ve got two problems, after a couple of weeks not using the starter battery flattens, if I try and start the van when the battery is flat the red fuse number 9 blows, any ideas why that is? There is not enough power to engage the starter motor, but the fuse will blow.
Sounds like you might have a short somewhere along the cable that runs the length of the van perhaps? Check where it passes through the chassis for signs of wear.
I should of said, but if the battery is charged the van starts ok and the fuse does not blow, it’s fine, it will only blow with a drained battery
Easiest check initially would be the terminals on the starter and solonoid. I can't think why a low charge battery would cause the issue that a full battery doesnt, but eliminate the easy stuff. If you can, take the terminals off the starter, give them a good clean up and tighten (disconnect battery first) check the earth also. Do you have a hot start relay fitted? This would reduce the current flow through the ignition circuit so may eliminate the fuse blowing, but is a "band-aid" for the problem rather than a total fix.
If you have a stereo try disconnecting it. The fuse that blows is powered off the battery. Its probably a partial short, drawing about the fuse blowing current. The longer you leave the bus the hotter the fuse gets until it melts. You come back and try to start the bus, then find the fuse blown. Try feeling the fuse .. carefully think several hundred degrees C .. when you first fit it. It may be hot already.. The battery is flattened because the fuse takes several hours to blow. So you have a parasitic drain on the battery from an almost short. Maybe its something whacky like a melted buzzer if it was a USA bus. Or a stereo, or a trapped wire on a disconnected internal light... Its downstream of that fuse.
