Installing Tekonsha P3 Brake Controller # 90195 in 1999 E450 Class C Motorhome

Question:

I found the correct brake controller plug up under the dash, the blue factory wire goes up into the wire bunch and I cant tell where it goes. It does not come down with the bunch that goes along the floor board and back into the coach. The tail light and turn signal wires are there, but no blue brake wire. Do you know where the factory blue brake wire goes from the controller connector? Would like to know before I cut and splice into it right at the connector. Thanks

asked by: Rob K

Expert Reply:

It certainly may be that the wiring from the under dash brake controller port is not routed all the way to the trailer connector at the back of the motorhome. If there is a 7-way connector on the back of your coach you can try tracing the blue brake circuit wire forward from the connector; you may be able to find a point where it can be connected to the wiring from the front of the vehicle.

You can also run a new brake output wire from the back of the P3 directly to the trailer connector at the rear of the motor home, bypassing the vehicle's wiring. You will want to use existing wire grommets if possible and to keep the wire away from moving suspension and hot exhaust components. The wire carrying the brake controller output will connect to the 7-way pin at the 5-o-clock position (as viewed from the rear of the vehicle, please see the linked photo). You will want to use 12-gauge (or larger 10-gauge) wire such as # 10-1-1 and quick splice connectors # SWC501915-1.

You may also need to install fuses in the power distribution box in the engine compartment to activate the power circuit for the controller. Look for fuse receptacles labeled trailer or tow. I have also linked articles on wiring and brake controller installation for your review.

expert reply by: Adam R