Lost Power To 7 Spade Trailer Connector

Minelab2004 · May 3, 2011

Hi all, I am new to the forum and hope that I put this question in the correct forum. I have owned my 2004 Silverado since new. It came with factory installed 7 spade connector for towing a trailer. I have a problem now where I get no power to the connector. This probably happened when I borrowed a trailer from a friend. I plugged in and the lights worked and at some point during that trip they went out. Now, a year lager I own a trailer and want to wire it up to use on my truck. I bought a heavy duty 7 spade pigtail that I will wire to my trailer lights.

I found that there is no power to the 'pos' terminal on the connector (the spade at about 1:00 O clock when looking at the connector). I disconnected the female off of the back of the connector and everything is clean, no power there either. Since it did have power at one time I looked in my owner manual and identified a blowen 10A 'TRL' fuse in the under hood fuse box. I replaced it and still no power. I checked all other 'TRL' fuses in that box as well as the fuse box located in the cab on the driver side of the dashboard and no blowen fuses.

Would there be any other place that I could look to see why there is no power to that connector. A friend who owns a 2003 HD told me that there is a fuse in the rear tail light on the driver side. I appreciate any thoughts you may have on this.

sonjaab · May 3, 2011

GM changed the power pinout in 03 so you prob. blew out

some fuses because the wiring is incorrect!

But check your underhood fuse center for the big 30 amp.

maxifuses in either the Stud #1 and Stud #2.

I bet one is popped!

I went thru this when I tried to use my 01s 7 to 4 connector

on my 04 and popped a bunch of fuses!

http://64.91.234.154/coppermine/albums/use.../03~05-UBEC.gif

Minelab2004 · May 3, 2011

GM changed the power pinout in 03 so you prob. blew out
some fuses because the wiring is incorrect!

But check your underhood fuse center for the big 30 amp.

maxifuses in either the Stud #1 and Stud #2.

I bet one is popped!

I went thru this when I tried to use my 01s 7 to 4 connector

on my 04 and popped a bunch of fuses!

http://64.91.234.154/coppermine/albums/use.../03~05-UBEC.gif

Thank you very much for the info. I will check that one out. If it is blown do I need to go to my dealer to get one? I am using the heavy duty 6' ping tail but I will only be wiring up three of the wires as all my trailer has is running light, stop, turn. I like how that pig tail is pretty solid and locks in place. Thanks again.

c4cruiser · May 3, 2011

Thank you very much for the info. I will check that one out. If it is blown do I need to go to my dealer to get one? I am using the heavy duty 6' ping tail but I will only be wiring up three of the wires as all my trailer has is running light, stop, turn. I like how that pig tail is pretty solid and locks in place. Thanks again.

Actually, you will need 4 wires for basic trailer lighting. tail lamps, left turn, right turn, and a ground wire. The GMT800 trucks have separate turn signal bulbs so if you don't use the OEM circuits, you may have problems with the turn signal lights and stop lights.

Fixing the factory trailer wiring will be the best way to go. You can find 7-pin RV to 4-pin flat adapters for about $8 that will take care of the separate turn/stop lamp setup.

Minelab2004 · May 4, 2011

Thank you very much for the info. I will check that one out. If it is blown do I need to go to my dealer to get one? I am using the heavy duty 6' ping tail but I will only be wiring up three of the wires as all my trailer has is running light, stop, turn. I like how that pig tail is pretty solid and locks in place. Thanks again.

Actually, you will need 4 wires for basic trailer lighting. tail lamps, left turn, right turn, and a ground wire. The GMT800 trucks have separate turn signal bulbs so if you don't use the OEM circuits, you may have problems with the turn signal lights and stop lights.

Fixing the factory trailer wiring will be the best way to go. You can find 7-pin RV to 4-pin flat adapters for about $8 that will take care of the separate turn/stop lamp setup.

Thanks for that info. As far as lights on my trailer it has stop, rh/lf turn, running. I removed all the wires and am going to re-wire it myself. I bought a new 7 spade pig tail with all wires coming out of it. I labeled each wire according to the diagram on the truck connector so that I know what each wire is for. I won't be using all of them. I prefer to use the 7 spade connector directly to the truck so that I can avoid an adapter as well as avoid any adapter issues. Now I just need to figure out how to get the power back to that connector.

I put the continuity meter across all fuses and none are blown. I also looked at the under the hood fuse box and stud #1 has a red plastic plug in it. I'm guessing that my friends trailer was messed up and must have blown something else in my system. It lit up for about an hour so I know there was power back there. I replaced one 10A fuse that was blown but still no go. I may end up having to take it in for diagnosis if I can't figure it out ughh

nickvrebel · May 4, 2011

why put a 7 way on the trailer? that's only needed when the trailer has brakes, it's really pointless, a 4 to 7 way adapter accomplishes the same thing and keeps it possible to hook the trailer to some older trucks without a 7 way.

the fact that the "+" circuit is not live has nothing to do with the trailer lights. That circuit is only used to charge on board batteries for RV's and brake controller break away boxes. you won't be using that circuit.

Minelab2004 · May 4, 2011

why put a 7 way on the trailer? that's only needed when the trailer has brakes, it's really pointless, a 4 to 7 way adapter accomplishes the same thing and keeps it possible to hook the trailer to some older trucks without a 7 way.

the fact that the "+" circuit is not live has nothing to do with the trailer lights. That circuit is only used to charge on board batteries for RV's and brake controller break away boxes. you won't be using that circuit.

I have never hooked up trailer before so this is new to me. So I don't need that '+' terminal to work in this case? My directionals, running and brakes should come on and be powered up when they come on right? I just need to use the 4 way adapter and then connect up the ground, RH, LH, Running wires accordingly? I should be able to test this by putting my meter probes on the ground terminal and to say RH directional terminal and put on the directional and see the meter move with the directional correct? ... sorry if this is dragging out

nickvrebel · May 4, 2011

correct. on a trailer without electric brakes all you need is the 4 wires: L Turn, R Turn, Running lights and ground (brakes are both turn on at the same time).

The positive terminal is just used to charge a battery or power other items on the trailer, it is not used for lighting.

this link has a ton of info, way more than you need to know, but if you are in the learning mood....

http://www.etrailer.com/faq-wiring.aspx

this adapter is all you need:

http://www.etrailer.com/Wiring/Pollak/PK12716.html

That wire you are trying to test may not even be live from the factory, I know on the GMT 900 they are not (requires connected the end at the fuse panel and installing the fuse)

06Voy · May 4, 2011

I know you said you checked the TRL fuses but did you check all of them in both fuse boxes?

Minelab2004 · May 4, 2011

correct. on a trailer without electric brakes all you need is the 4 wires: L Turn, R Turn, Running lights and ground (brakes are both turn on at the same time).

The positive terminal is just used to charge a battery or power other items on the trailer, it is not used for lighting.

this link has a ton of info, way more than you need to know, but if you are in the learning mood....

http://www.etrailer.com/faq-wiring.aspx

this adapter is all you need:

http://www.etrailer.com/Wiring/Pollak/PK12716.html

That wire you are trying to test may not even be live from the factory, I know on the GMT 900 they are not (requires connected the end at the fuse panel and installing the fuse)

Ah yes the light finally came on in my brain when you mentioned about the '+' terminal and not needing it. I thank you kindly for all your help. My next move when it stops raining out is to put my meter on the RH turn and to ground and see if the meter moves with the directional flasher. I bet I was testing this all wrong. I am going to get the 4 way adapter too. I will keep you posted and thanks to all for being patient.

Minelab2004 · May 4, 2011

I know you said you checked the TRL fuses but did you check all of them in both fuse boxes?

Yah I did check fuses on both under hood and inside cab near the driver side door. We may be on the right track now that I understand what I should be looking at for this wire job.

Minelab2004 · May 5, 2011

Thanks to everyone here. I turned on the LH directional and put the meter across the neg terminal and the LH terminal and the meter moved. I think I am good to go. Being a newbe at wiring really shows. Put a wrench in my hand and a different story for sure! Hopefully the 4 way adapter will align up to the correct pins on my 7 way so that the wires will run the correct lights on the trailer.

nickvrebel · May 5, 2011

the adapter will have a little nipple, a nub if you want to call it that, it points up. this protrusion locks it in place with the cover for the plug hole on the vehicle, if you line that up it can't be inserted wrong.