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Ron, ASE Certified Technician
Category: Ford
Satisfied Customers: 23001
Experience:  23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
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I am attempting to wire a 7-wire Trailer plug on my 1989

Customer Question

I am attempting to wire a 7-wire Trailer plug on my 1989 F250 supercab-with a 460 engine and 5 spd manual tran.
The truck lights and Camper lights (camper circuits tap into The Truck circuits at the front of the camper) seem to work fine.
There (8) separate wires-in the truck lighting harness designed for a 7 wire trailer plug. I have not been able to get these wires life. On the Lf hand engine compartment, there are a number of Relays--including a Trailer Towing Relay. I just Replaced this relay-with no change--in any of the simple circuits (Lf, Rt turn, running lites,back up, 12v hot, ect circuits. Open for a good direction in finding the missing relay, tkx phil
Submitted: 7 months ago.
Category: Ford
Expert:  Randall C replied 7 months ago.

Hello, what is working and what is not? and I need all the wire colors you have on your end in the harness you say are 8 wires

Customer: replied 7 months ago.
Randall, there are 12 wires in the original bundle.
The following are working for the truck-with the Camper tapped in each at the front of the bed
1. Green/org - Lt turn
2. Brown - Running Lites
3. Orange/blu - Rt turn
4. Blk/pink - Back upThe following are the trailer circuit and are not working
5. Black/pink - Back up?
6. Yellow - 12V
7. Red/grn - Taped
8. Lt Blu/blk - El Brakes
9. White - Ground
10. Green/or - Lt Turn
11. Orange/blue- Rt Turn
12. White/red - Tail Lite
hope this helps phil
Expert:  Randall C replied 7 months ago.

I am sorry I am confused, You have a bundle of wires, have you tried to tap into any of them? you said no power on any of the wires. I just need to know what the wire colors are on the truck side only, and what ones work with power and what ones do not, I am sorry in that I am not following what you mean by front of bed, camper, trailer circuit etc

Customer: replied 7 months ago.
Randall--as noted, there are 12 wires in the bundle--4 of them supply turn, stop, runnng lites, and back up at the back left side of the truck. The camper tied into these wires for its markers, turn, back-up and stop lites. Also at the back, left side of the truck are the other 8 wires, in 2-4 wire connectors. at the wrecking yard, I found a 91 ford with a wiring harness that plugged into these 2 connectors to feed a 7 wire -standard Trailer plug. I believe there must be a Relay that is currently keeping these wires dead. Under the hood, on the right hand side, there are several Relays. One of them is marked Trailer Towing Package. Today, I put in a new Relay--but still no power. Hope this helps. I would be glad to discuss on the phone, but am hesitant to pay an additional $26 on top of the $36 already paid. hope this helps phil ***-***-****
Expert:  Randall C replied 7 months ago.

sorry I was off all day, I am very good at wiring but this one has me a bit off as the diagrams on my end are rather vague, Best i opt out and open the post to the other experts, One should be along soon to help, Sorry I could not

Customer: replied 7 months ago.
Randall--I appreciate you trying to help--and refering me on. This is a challenge--I have reached out to several sources--with limited success. As I mentioned, there is a Trailer Towering wiring Relay-which I replaced--but I have not been able to identify what activates this relay-so the trailer wiring becomes live. phil

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