Power to trailer from GM Tow Vehicle - Montana Owners Club

Dave e Victoria · 02-12-2006, 09:58 AM

Just found out why I never had 12 volt power through the seven way connecter to the trailer. Seems GM puts a dummy fuse in the post one location (Under hood fuse box top left position).
Dave

Emmel · 02-12-2006, 11:42 AM

Dave, there is a place for a 30amp fuse in that box. This fuse must be there to supply power to the charging system when the tv is hooked up to the Monty. The truck dealer said it was not necessary in my truck since I have two batteries. You must have it, seek someone that can help you at your city, a mechanic you trust.

steves · 02-12-2006, 12:03 PM

The same thing happened to my friend on his first rip in his GMC3500. His battery would not charge from the truck, he called on-star and they sent him to a local dealer who replaced the dummy fuse. Fixed the problem.

Dave e Victoria · 02-12-2006, 01:55 PM

Emmel,
I think that is what I said. Actually I have the dual battery option and still needed to replace the dummy fuse. The 30 amp fuse you are referrring to is for the brakes. That is in the position nearest the fire wall. The one for the power is the nearest the radiator side of the fuse box.
Dave

DHenry · 02-12-2006, 02:04 PM

How long have they been putting that dummy fuse in there? I have a 2002. What does it look like?

kdeiss · 02-12-2006, 02:53 PM

If I remember the fuse was taped under the dash or with the plug and pigtale for the brake controller. I remember installing in the fuse box under the hood of my 2002 GMC

Montana Sky · 02-12-2006, 03:43 PM

Dave,
Thanks for the heads up. Will have to look into this.

Doug,
I was wondering the same thing, I went out and looked at the fuse box was not sure which is the one for sure. I have an oil change on Wednesday, I will ask the dealership to check this out.

Dave e Victoria · 02-12-2006, 04:38 PM

Ken,
The fuse taped under the dash or to the plug and pigtail is a thirty amp fuse for the brake circuit. It is the one that goes in the front position nearest the firewall.. The dummy fuse is on the other end of that row. The dummy is square like the other heavy duty fuses on that row BUT it does not have a window in the top. The proper fuses have a window through which you can see two solder bumps and and two copper bridges. The square plastic housing is smooth. (Auto stores sell a similar looking fuse that has small ridges on the sides. This is the wrong one.}

This position, called "post 1" , can handle up to 60 amps. Personally, I installed a 30 amp to start. I can always go higher if need be.

Doug,
I'm not sure how long they have been doing this. Just see if you have 12volt power on the correct pin in the seven way connector to the trailer.

The fuse panels are widely used through out the GM line. That is why some of the fuse lableing seems strange. For instance, some of the fuses are labled for HID which is the blue/white headlights used in the Escalade. There is even room for the HID relay.

Bill and Ann · 02-13-2006, 02:20 AM

Dave: For info and from experience I recommend you put in a 40 amp fuse in post 1. I have already replaced 2 30 amp fuses because they have blown. I didn't notice they were blown until I found my batteries weren't charging. Happened twice. No problems since I put in the 40's.

kdeiss · 02-13-2006, 02:56 AM

Quote:

quote:Originally posted by Dave e Victoria

Ken,
The fuse taped under the dash or to the plug and pigtail is a thirty amp fuse for the brake circuit. It is the one that goes in the front position nearest the firewall.. The dummy fuse is on the other end of that row. The dummy is square like the other heavy duty fuses on that row BUT it does not have a window in the top. The proper fuses have a window through which you can see two solder bumps and and two copper bridges. The square plastic housing is smooth. (Auto stores sell a similar looking fuse that has small ridges on the sides. This is the wrong one.}

Dave you are correct it has been 4 years i just remember installing a fuse

This position, called "post 1" , can handle up to 60 amps. Personally, I installed a 30 amp to start. I can always go higher if need be.

Doug,
I'm not sure how long they have been doing this. Just see if you have 12volt power on the correct pin in the seven way connector to the trailer.

The fuse panels are widely used through out the GM line. That is why some of the fuse lableing seems strange. For instance, some of the fuses are labled for HID which is the blue/white headlights used in the Escalade. There is even room for the HID relay.

Dave e Victoria · 02-13-2006, 03:48 AM

Bill and Ann,
Thanks for the fuse sizing. Turns out i have a spare 40 and will install it.
Dave

Montana Sky · 02-13-2006, 11:56 AM

Well if I am looking at the right fuse it seems I have a 60amp fuse already in there. I did take a look at the rest of the fuses and they are all clear and I can see both copper solder bumps. Will have shop double check this Wednesday when truck goes in for oil change. Thanks Dave for bringing this up, not sure I would have found this otherwise.

CRUZIN 2 · 02-16-2006, 02:32 AM

I was one who went out and checked my fuse to see if it was installed, I'll bet that I wasn't the only one to check it. Guess what, you guessed it no fuse. This is a GREAT web site and tool.

Larry & LaVonne

Montana Sky · 02-16-2006, 09:29 AM

The dealership checked the fuse and found that there was a 60amp in place. The said it was too much and replaced it with a 40amp fuse.

Larry & LaVonne,
Dont you just love all the information and people on this site, I have learned more from here than I think I could have ever done on my own.

Dave e Victoria · 02-16-2006, 12:50 PM

That's interesting. The decal on the inside of the fusebox cover on my truck says it should be 60 amps. Of course that is maximum. One thing to note, as a design principle, fuses should be sized to protect wiring not what is connected to the wiring. Things that are connected should be properly protected by their own design. I wonder what criteria your dealer used!!!
Dave

MIMF2 · 02-18-2006, 12:05 AM

Hey gang, how is that fuse labeled? I've realized lately that my recept isn't providing auxilary 12 volt power either. I know that it use to. Must have blown the fuse a few weeks back when I had to transport a repair unit.

Dave e Victoria · 02-18-2006, 02:26 AM

In Bubba, the fuse is labled "STUD 1". As you stand on driver's side facing engine compartment, it is in the ro closest to the engine and all the way to the left. It is a square about 3/8 inch on a side. You should be able to look through the window on the top of the fuse and see if it is blown. If there is no window, it is the dummy.
Dave

Note corrected the terminology -- it is stud 1 not post 1

MIMF2 · 02-18-2006, 02:37 AM

Dave,

Thanks! I recall seeing that. Going to go check it out in a few minutes.

Wind chill is 12 below!! So, I think I will plug Max in and let him warm up a bit.

rlwhit · 02-20-2006, 01:28 AM

The plastic dummy is there. Just don't understand why GM does that and that the dealer is also a dummy. I could not figure out the other day why the slides ran the battery all the way down after towing all day. Had the furnace on due to severe cold weather. Thanks Bill for the info.

tweir · 02-21-2006, 04:26 AM

The reason the factory installs a "dummy" fuse is to protect individuals when they are wiring up pigtails/recepticles---this way an errant loose or bare wire won't short out. Once all of the connections are made, then you "heat' the circuits---its just one of those safety things. "Smoke-testing" a wire loom is not a good thing...!

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