Ford F-250/ trailer question

[09 arctic cat m8]

Hey guys three times with three different trailers I've had them plugged into my 7way plug and three times now my truck will not start, and it's not the battery as it always starts anyother time, now it doesn't always do this but it ussally does it when I'm hooked up to my b train, either my 5th wheel and boat or 5th wheel and quad trailer, it also did it with a flat deck trailer, the radio and lights all work it just won't crank almost acting like a dead battery but once I boost it it's back to normal, any suggestions!?? Thanks

 

[Cdnfireman]

If the truck is fine with no trailer plugged in then obviously the trailer has a wiring problem that draws down your battery. Does your truck have a factory trailer package or did someone wire it later with the trailer plug ?

 

[09 arctic cat m8]

all factory wiring, and ive never had it happened when im just hooked to my 5th wheel alone

 

[papajake]

with the truck running check plug on truck seven plug, top centre ground top, left taillights, top right reverse, centre electric brakes, bottom left right turn & brake, bottom right left turn & brake, bottom centre power too trailer battery, there might be a ground in the wiring to the plug

 

[campingnut]

Is the battery low in the 5th wheel and the charging circuit in truck always hot to the trailer. Is the trailer brake controller always hot. I would check for power at either one of those 2 terminals at the trailer plug when the key is off.

 

[arff]

Possibly the trailer electric brake is drawing power

 

[imdoo'n]

it only happens when you have the second trailer hooked up? I would start looking at wiring at rear of 5th wheel and tag trailer. pickup a trailer wiring plug checker and go from there.

 

[HotShotHarry]

I agree with indoo'n, Check the plug on the 5th.

 

[Zrock]

Ya definitely check that last plug.. Also what year and diesel or gas truck. I know the diesels sometimes can be very fussy on their starting voltage. May have a battery thats on its way out and does not show up under normal usage but when you have all the trailers hooked up the extra voltage draw is just enough. Have you had the batt load tested?

 

[09 arctic cat m8]

its a 2011 ford f250 6.2 gasser, i tested the truck battery its 40% im guessing thats the cause of it, thanks everyone who helped i tested my 5th wheel plug at the shop an found nothing outta the normal, must be the truck battery