I have a 2007 expy with the tow package. I plugged in a trailer and no lights work whatsoever. I checked the fuses and they are all good. Anyone have any ideas? Can someone email me a wiring diagram for this part of the electrical system? my email is justin at constructpoint.com

thanks in advance.

 

which harness are you trying to use?

the 4 pin or the 7 pin?

if the 7 pin, sometimes you have to connect the trickle charge wiring and there is a relay that gets used. For some reason some Fords already have it connected, and some don't


edit: otherwise, you need to check voltages

you can get a cheap voltmeter for about $10-15 at Walmart/Parts Store. At the connector itself, check for voltage.

Also, check your trailer wiring itself. If the pins are corroded, or improperly grounded you won't get any lights

 

I tried it on both the 4 pin and the 7 pin with an adapter (trailer was 4 pin). I need a wiring diagram to know what the meter should be reading. Maybe its a relay problem. Need diagram to troubleshoot.

We tried the trailer on my cousin's Suburban and the trailer works. It was embarassing that my Ford ultimately couldnt trailer the boat and we had to use his truck.

 

Ford follows the standard wiring convention for 4 pin connectors. I went out and checked my Expy and F-250. They both follow the same color pattern

ground - White wire
left - Yellow wire
right - Green wire
brake - Brown wire

here is a good diagram for the standard trailer wiring setup
Trailer Wiring Diagrams | etrailer.com

 

Check the truck wiring where it plugs into the back of the 7-pin. The connector on my 07 expy was not fully seated in the back of the 7-pin plug.

 

Thanks. I was looking more for the internal wiring in the truck from the trailer connector to the fuses/relays, etc.

 

Wasnt getting any voltage from ground to the running light pin on my Fluke. Went through all fuses and they were good. I pulled the relay for the parking lights and swapped it with the starter relay. Then I got voltage at the trailer connector. I swapped the relays back to double check but now the old relay worked. Im not sure if the relay just didnt have a good connection or there is an intermittent issue in the relay. I kept it swapped with the starter relay figuring it will be used very often and if it fails it will be obvious and I can always swap it back so I wouldnt be stranded. I will price this out and if its cheap enough will just order the replacemnt relay.

I am unclear how this would affect turn signals though. It would seem to me the only thing that should affect all of the items is if there is a ground issue.

 

no idea man...sometimes electrical stuff is just confusing. there might have been some slight corrosion on the contacts. just you moving the relays around cleaned them up?

I wouldn't question it. It might blow up in your face