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Inverter problems

Thread starter #1
I'm asking this out of curiosity.

I work at an ambulance service and some of our trucks are equipped with inverters that are supposed to keep our equipment charged when plugged in to a shoreline. I've noticed that one of these trucks the shoreline only keeps the truck charged about half the time.

Another one doesn't keep charge at all when it's plugged in, when asked about this I was told that it was because "someone," disconnected the inverter and all the wires coming out of it were the same color and gauge. I was also told that without schematics there's nothing we can do to fix it ourselves.

So all that being said, is there any way to troubleshoot this situation?

Sorry for the long post


Well-Known Member
disconnected? ... got photos?
keeps charged half the time? ... so it still runs when the truck engine is off? .. but only for half as long?


Well-Known Member
Most Helpful Member
Can't you copy the wiring from a working truck? Normally, if wires are the same colour they their polarity doesn't matter - such as A.C. out. Pictures?

Thread starter #4
Hopefully I can clarify.

The shoreline is like an extension cord that connects the truck to the building power. We plug it in when we're at station, we turn the truck off and plug in the shoreline. That is supposed to keep the outlets in the back of the truck usable, hence keeping equipment charged.

Truck A) the truck that charges half the time, what I mean by that is, we can plug it in on Monday night and it will charge overnight but plug it in Tuesday night and it won't charge. This could be as simple as user error, not making sure the shoreline was fully plugged in.

Truck B) the truck that has the wires disconnected from the inverter. So it doesn't matter if it's plugged in or not it won't charge.

But both charge when the trucks are running.

I will get pictures when I can, but until then I hope this helps!
Thread starter #5
I was thinking about doing that but I was told that we would have to know where the other end of the wires out of the inverter are in order to test them and get them put in the right place.

It's been a little bit confused. I will get pictures as soon as I can.


Well-Known Member
Most Helpful Member
I would guess that the inverter takes care of which power source is being used. Shore power or battery power via the inverter. This would mean the inverter would require 12/24V DC in, AC in and AC out. As the truck charges when running this suggests that DC in and AC out are both connected and just the shore power isn't.

Will await pictures.



Well-Known Member
a) yes , most likely that there is a loose wire/connection on the shoreline bus. which would run in to a step down adapter and charge the cars battery
an ohm meter can test this easily (when there is no electricity on the wires)

b) inverts usually run off of the 12v battery , and output 120v on the ac plugs. as mentioned , since we cant trace it from the other truck ... i wonder if we can open up the inverter ... usually inverters will have larger guage wires for the pwr/gnd that would narrow it down to 2 wires... if we can open it up finding out which one is ground should be simple from a visual

i would recommend against trial and error as i am doubtful that an inverter has protection against reverse biasing the way car chargers do

also what kind of inverter? how many watts?

btw ... i was only in a ambulance once when i though i was dying ... i am only relying from the little i know with other service vehicles
Logically, if all wires were the same color and gauge, an ohmmeter would identify each wire feed. A marker or tag to identify each wire makes troubleshooting more effective. As per the connector, does it have a lock to prevent unintentional removal from the socket?
Just make sure you don't exceed the 1,000 watts the inverter is rated at. Keep an eye on your car battery. Drawing 1,000 watts from a 12 volt battery means about 85 amps. Even a heavy duty car battery wouldn't last very long at that discharge rate.

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