Does the Power Wire Need to be Run to Battery to Install a Wiring Harness in a 2005 Saab 9-5

Published 05/22/2014

Question:

Re : 2005 Saab 9-5 aero wagon , without the manufacturer installed trailer lighting harness. Therefore I ordered a hitch from you with a C59496 wiring kit. Saab has lights on 24/7 when driving and trailer will have Led lighting small alu 4x8 utility trailer Question : Instead of running a cable from the unit to the battery post I intend to hook it up to the cigarette lighter in the rear shorter , easier to get at from the trunk . The two cigarette lighters are on the same 30 A fuse but according to Saab should not run more than 20 A together. The other one front will only be used to charge an I-phone so let’s assume 5 A max. That would leave 15 A for the 119179 unit which is fused at 10 A as far as I can determine. So that leaves only one potential problem : The cigarette lighters are only powered when the car is running which I guess is an advantage because there will be no battery draw when the car is not running. Is there a reason that you recommend connection to the battery with 24/7 draw or is my solution acceptable ? If so should I wire ground to the cigarette lighter ground or to chassis Tks yr reply

asked by: Jan D

Expert Reply:

The reason you need to run the power wire to the battery is because the # C59496 uses your tail light circuits as signal wires and actually powers the tail lights of your trailer with the power it draws from the battery of your 2005 Saab 9-5. This protects the delicate tail light circuitry by not overdrawing it. If you were to run the power wire to anything but the vehicle battery you would be defeating the circuit protection of the converter.

I also attached an FAQ article on running the power wire for a trailer wiring harness.

expert reply by: Jameson C