hidden Trailer Running Lamp Relay

[davesomers]

can someone help me find this relay?

I've got a 1999 F350 Crew PSD with the Trailer Tow package.
I have no electricity going to the marker lights on the trailer. (no it's not a trailer problem, it's not corrosion in the connector, and it's not a ground.) I do have Left, Right, Backup, Charge, and Brakes on the trailer. and I do have marker lights on the truck.
Playing along with the Factory Service manual's diagnosis steps, I get to the point where it has me check the "Trailer Tow Parking Lamp Relay". The Factory Wiring Diagram shows it at "I/P Relay Block".

In the everyday owner's manual, there's a "Passenger Compartment Fuse Panel" below the steering wheel, in which you find "Interior Lamp", "Not Used", "Horn", "Power Window", and "Accessory Delay" relays. and there's a "Power Distribution Box" under the hood, in which you find "PCM", "Blower", "Injector", "Washer Pump", "Wiper Park", "Wiper Hi/Lo", and "PCM Diode" relays. Next to it are two external boxes, one with the "Tow Backup" and "Tow Charge" and the other with "ESOF1" and "ESOF2" relays.

BUT NO WHERE HERE CAN I FIND THE "Trailer Tow Parking Lamp Relay".
Can someone point me towards it? (and which one it is?)

Dave

[bigcountrysg]

Welcome to the Org. I don't know if they are the relays you are looking for. How ever there is two relays under the radio. If you lay down on the driverside floor board. Look up under the dash where the radio is. There is two relays hidden there. I know one is for turn signals. But I do not know what the other relay is. Both relays look the same. It is worth a check at least. No you do not need to tear your dash apart to get to these relays. At least this is how it is on my 2002.

BTW welcome to the Org. I am sure others will have more ideas for you.

[wetco416]

It says that it is location #8 in tthe underhood fuse box,it is a 15 amp mini fuse

[davesomers]

BigCountrySG gets the gold star on this one. OohRah.
At least as far as knowing where the relays were hiding. But they are MUCH easier to reach by pulling the radio (5 seconds with the right tool) and reaching in and down. My forearm couldn't bend in the right places to come up from below.

Stuck a new relay in and 'poof' the trailer marker lights came on.

Just for completeness (for when someone else searches the archives with the same question)... On a 1999 SuperDuty, the Trailer Marker lights and Trailer Backup lights share fuse #4 in the underhood power distribution box (20A mini). The Trailer Backup lights come thru the relay that's just outside the distribution box. (and since they worked I knew it wasn't the fuse.)

Dave

[Blue01F250]

Awesome that you found it man and WTG BC! I was thinking it was an underhood one - but now I will know where else to look - This place is great!