Ambulance Wiring/electrical Isolation Question


New member
Hello all. Tried to search this the best I could, but no total luck. I have an e-350 1990 ambulance I bought. It has two batteries under the hood. It runs to a master disconnect/kill underneath drivers seat. This master switch kills everything to the truck. From there I also have a switch on the ambulance siren/lights panel that is a master for the box. If I wanted to have a dedicated battery bank charged up by the alternator, and have the box run only off the new battery bank, what would be the way to do all this? Apologies if this was discuss somewhere else, but I cannot find it super clear.
Hunt up Blue Sea's website (, and check out their battery combiners and isolators. I, as well as many other any emergency vehicle upfitters and ambulance electricians, use Blue Sea equipment.


Expedition Leader
The module master switch will control a good size solenoid somewhere. If you pull the incoming 12v supply from that and run it to your house bank. If you don’t care about the module control then just feed the house battery to the output side of the solenoid.

I believe the module master switch actually switches the ground on some vehicles and if so you may want to feed the solenoid control with a positive from the house battery bank as well.

As far as charging from alternator. I would suggest you check out the Redarc products or the $50 thread mentioned previously. I personally like dc-dc charging instead of a solenoid but each to their own on this one.


New member
Thanks for the replies everyone. Gonna have to open up the center console/hood/switch panel and take a look. Hardest part I forsee is running new wiring to whereever the battery bank will be.