Tow vehicle 50 amp fuse blowout

[Dui]

50amp mbec1 fuse has blown twice this week on my truck. Both times I was hooked up to my trailer. Can using the 12 v pump toilet while being hooked up to the trailer cause this? Any ideas...at a loss?thanks in advance. Fuse protects passenger side windows, power seat and trailer harness. Trailer and truck batteries verified good.

[H. John Kohl]

Dui,
I believe you have a intermittent short on your 12V feed from your truck to the trailer. I think a wires has rubbed the insulation off. I would check the wiring splice box at the hitch pin where umbilical cord is spliced into the trailer. Then back to your battery. No I do not think using the pump should not be a problem as long as your trailer battery is charged.
So Check the status of your trailer battery and if good look for a wire issue.
Good luck.

[mhs4771]

X2 John's post. Our GM uses a 40 amp fuse, but the trailer harness is the only thing on it. But I can run the hydraulic pump to put down the front landing gear without a problem.

[Art-n-Marge]

Using anything on the trailer while connected to the TV should never cause this UNLESS there is something wrong like a short. Only a high surge of power like from a short somewhere between the RV and the TV.

In your case, when the RV pump was used and you were not connected to shore power, the RV batter(ies) provided the 12V. But you were also connected to the TV. There is an auxiliary (hot wire) that also provides 12v to the RV when connected and is typically used for recharging the batteries and should be able to handle the high amps of an RV. After all this is how one raises landing legs, or operates slide outs which draw some pretty high amps when the RV batteries or low, bad or not present. When I've done this I keep the motor running so the batteries aren't drained too quickly.

Knowing this I hope you can debug the problem. I'm thinking I'm X3 on a short somewhere and I hope you can trace the rats nest of wiring. I'd start with opening up the connectors and check for shorts. Another possibility is rats or mice love the taste of insulation and a wire somewhere is exposed.

I've had connector and connection problems before and others have had rodents.

[Dui]

Thanks for all of your responses, we ended up finding the short underneath the driver power seat. The insulating jacket on one of the wires was cut back leaving the bare wire exposed. Once the wire was insulated and fuse replaced, everything has been working properly.

[H. John Kohl]

Glad you found it.

[Dui]

Me too. Thanks to everyone for your help. Dui