# 1990 mccoy miller ambulance, ford e350



## blackturbo (Oct 17, 2016)

Hi all,
please forgive me, iam not an EMT. But i cannot find any answers from the basic ford website, as nobody knows about ambulances. Iam hoping, a mechanic that works on these things can answer my questions. I use my ambulance to haul dirtbikes and 4 wheelers and my computer business, . the reason I chose to buy a used ambulance was it was already wired up with electrical outlets for my computer repair business, and buying a used ambulance, I had a sense, every aspect of the vehicle was maintained all its life.

It has seem both batteries become discharged after a few days of sitting, even know the main battery switch is in off position during its sitting times. I have taken steps to diagnose, that yes, even with the master battery switch being in the off position, the batteries still have a 1-3 amp draw on both of them, which is the reason its killing them. the engine block heater is disconnected. I have to manually disconnect the batteries. with the main battery switch in its off position, nothing works, . but since my batteries are dying after sitting, i tested them, with the main switch in off position and the batteries are still getting a draw from somewhere. So I have to manually disconnect the batteries at the post to keep them from dying when it sits. So its something between the main battery cables and the main battery switch inside the cab. and its difficult to trace cables . but it seems there is something between this point. maybe somewon can tell me. thanks ! If i disconnect the main cables from the batteries, the batteries still hold their charge for more than 2 months or so. so something between the main cables and the main battery switch has a drain. maybe somewon knows what this is, as with the main battery switch off, the truck is basically dead, it doesnt do anything even with the key on. so one would think its all off, but it isnt, there is still a current draw somewhere. 

mark


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## Handsome Robb (Oct 17, 2016)

Chasing down an electrical gremlin in an ambulance sounds like a nightmare. There's so much going on electrically. 

Does your truck have a "mod power" switch on the center console? If it does turn that off as well and see if there's still a draw. That would at least narrow it down to being in either the cab or the module. 


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## blackturbo (Oct 18, 2016)

No, i dont believe so. it does have a master switch on the console, but that doesnt have any power with main battery switch in the off position. I really cant find anything with power with the main bat switch off. but there is a draw somewhere.


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## MRE (Oct 19, 2016)

My service has a 2003 McCoy Miller on an E350 chassis.  The "battery switch" on the vehicle only switches the accessories that were added to the chassis when it was built into an ambulance (emergency lights, radio, module (box) electrical systems).  All of the vehicle systems and non-emergency vehicle lights still work with it off.  It is possible that something was wired around the battery switch and is not disconnected when it is off.

Is this a new problem, or has it been there since you got the vehicle?


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## blackturbo (Oct 19, 2016)

No iam pretty sure it hasnt, ive own the truck since 2009 as it came out of service from a nursing home, and I purchased new batteries for it then, and it used to sit weeks at a time. When I got the truck, most of the systems were missing, like the expensive inverter system and the battery management system, which as I understood kept both batteries charged and even provided enough amperage to start the truck . But its only been since the last year this starting happening, as I have to totally disconnect my batteries now when it sits, even with the main battery switch in its off position, the truck isnt like yours, everything is dead as I see. even with the key in the ignition in the on position, its all dead. I do have a master module power switch, but even that is even dead with the main bat switch off. I guess really I will just purchase two battery cut off switches , its almost impossible to trace the battery cables. the batteries have been load tested and hold a charge for weeks like they were brand new if they are totally disconnected.


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## MRE (Oct 19, 2016)

Interesting.

At this point I would try to figure out which side of the battery terminals is being disconnected by the battery switch.  There may be some wiring which the insulation has worn through and is causing current leakage.  This could also be caused by severe corrosion connecting conductors that should be isolated.


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## blackturbo (Oct 19, 2016)

thats what Iam thinking, there is a huge metal thing with cooling fins on it, that alot of thick red battery cables are bolted to via a post like on a battery, that is near connected to the main battery switch (1,2, both, off) but its almost impossible to trace these cables between this and the batteries to see if anything else is connected. I dont even know how to test this metal box thing or whatever  its called, but the terminals are not corroded at all on it. I did call Mccoy Miller a few years ago on another thing, and they said really no truck is the same, as each technician building it and wiring it does things different. oh well, i  guess time for 2 battery cut off switches. Thanks for all these replies


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