I'm not sure where to seek help to solve this issue we are having with our 2008 E450 - converted to a 21 passenger bus. The reason I'm asking here and not taking it to a mechanic is our vehicle is maintained by our city but they cannot see the bus until the 30th and we need this bus to work before then for an important once a year trip. Part of the conversion includes a Carrier air conditioning unit for the occupants which is controlled by the stock AC controls.

The issue... in the last few months the under body cooling unit (see picture) would run well after the bus was off. The cooling fans started to run longer and longer with time to the point it would kill the battery (there's a stock battery as well as a secondary battery under the bus). Each time I connected the cables to jump start the bus the AC cooling unit fans would turn on. I pulled the AC fuse from the added fuse box from the conversion as well as the stock AC relay from the engine compartment and neither would turn off the unit. I then removed the negative lead at the cooling unit which stopped the fans. I thought that would be the temporary fix I needed but after charging the battery it was dead a few hours later! The two batteries were replaced 2-3 months ago. One more observation... below each of the fuses (in the conversion fuse box) is solder connection for something on the backside of the panel. The one for the AC fuse appears different then the rest - duller than the rest and flatter. Not sure if that observation helps.

Any help would be greatly appreciated and a possible trip saver!

Thanks for any advice ahead of time. Barry

 

Don't know how important it is to have A/C on your trip, but you may need to connect the fans manually, in order to have A/C while driving and then disconnect them manually ,as you have done, at the arrival point to prevent them running after parked a while until the vehicle is checked out. Add on systems are not all installed the same way and specific diagrams and info are usually required to diagnose malfunctions. Hopefully someone familiar with your vehicle's system will read your post and offer better help.