2nd Gen Non-Engine/Transmission factory 7 way connector

[mongoose]

I've been chasing wire problems with my factory 7 way connector for a couple of weeks now. I've narrowed it down to a short in the taillight circuit on the trailer it self. I've pulled the trailer for 3 year now with this truck and never had any problems.



I have since fixed the short on the trailer and still have no taillights. checking the 7 way plug, i have no power at the back of the truck, but the truck tail lights work. Looking through the wiring diagrams of the truck, it shows a 12awg wire (black and orange) going to the back for the tail lights on the trailer. my 7 way has a 16 or 18 awg brown wire that corresponds to the taillight pin in the plug.



In the connector located at the back of the driver side front fender, i found that i have the 12awg wire (black and orange) in from the PDC but not out the other side of the connector. My 12volt 12awg wire does the same, it ends at the connector and does not go all the way back to the back of truck either.



Should i cut these 2 12 awg wires from the connector and run them back seperatly using them to power the taillights on the trailer and provide a constant hot back at the plug for other uses?

 

[RustyJC]

Unless they have changed it on the 1999 model trucks, the taillight circuit for the 7-pin connector runs through a relay in the underhood power distribution center and is separately fused. Ditto the +12VDC battery power lead - no relay, but it is separately fused at the underhood power distribution center. This taillight setup is critical as the headlight switch cannot handle the additional amperage of the trailer tail and running lights.



If you have no power at the connector for taillights or +12VDC battery feed, I'll bet the short in the trailer harness knocked out the fuses and even perhaps the relay at the power distribution center.



Rusty

 

[mongoose]

from reading the wire schematic in the service manual, the 12volt power and taillight lead both use the same 40 amp fuse the PDC. the taillight is triggered by the relay in the PDC. I've got power to both 12awg wires down to the connector at the bottom of the driver side front fender. But that is where the 12awg wires end. The do not continue thru the connectors. Only 16 awg wires continue from the connectors to the back. The relay is good as well is the 40 amp fuse. I'm thinking I'll run some 12awg wires to the back and make the connection right at the connector at the fender.

 

[RustyJC]

OK, I missed that in your first post. If you have power beyond the distribution center, the problem must lie in the trailer tow harness between the front connector you mention and the rear 7-pin connector. Running new 12AWG wires between these connectors should fix you up, the only caveat being that the failure of the 16AWG wires in the harness didn't damage any of the other conductors.



Rusty

 

[mongoose]

Everything else seems fine. Brake lights work, turn signals, back up light signal, and trailer brakes work fine. Thanks, i think that is what i'll do, just run some heavy wires back.

 

[TowPro]

Did you pull the 7 pin connector apart to see if where the wire from the truck attaches to the connector is not coroded, or broken.



Not 100% sure if the factory connector can come apart, but its worth checking out.



In aftermarket 7 pin connectors, that is the first place I would have looked.

 

[mongoose]

The factory plug uses a modular molded plug for the back of the 7 way. I'm thinking i'm going to pull the factory plug and replace it with an aftermarket that i can attach the wires internally with. By doing this, i can use the 12awg wire from the taillights and not have to drop down to a 16awg at the connector.