The large ones are full size ISO relays, the smaller ones are half size ISO relays.

Available at any auto parts store.

Steve

 

Well finally decide to figure out which relay does what in my 97.

Heres my ASCII art rendition as viewed standing at left front fender

******************************
** *
* * *
* * *
* Rt Turn/BR * Lft Turn/Br *
* * *
* * *
* * *
******************************
* *
* *
* *
* CHARGE *
* *
* *
* *
******************************
* * *
* * *
* * *
* Running * Backup *
* * *
* * *
* * *
******************************
* * *
* * *
* * *
* Unknown * blank *
* * *
* * *
******************************

No clue at this time what the extra relay labeled "Unknown" is for....

Steve

edit; Dang it. Looked pretty when I typed it...

 

I have an '07 F150 Screw and on a recent camping trip with our 27' travel trailer, I blew the right side turn signal / brake fuse and the Battery Charge relay. Those are the ones I KNOW of, probably more. In reading this thread, it seems like this is a fairly common problem. Anybody know of a solution to this (other than keeping a supply of fuses on hand at all times)?

 

How do you unlatch the cover on the box under the hood?

 

Went through this with Steve, to add his notes to his picture ( aka he did all the hard work, I played admin on this one ).

 

Hope I'm in the right spot for this! I have a 97 F150 with tow package, I hooked up the brake controller (Hopkins 47225) and connected my trailer. I have all lights and signals as should be expected. I'm not 100% sure the controller is functioning, in fact I'm about 90% sure it isn't. I don't get the green light showing a connection. I've checked all fuses. I actually checked them prior to installing the controller and found the 20 Amp fuse in the mini fuse box under the hood blown. I replaced that one. Everything else looked good. In reading the forums I keep reading about the relays so I guess my question(s) would be could a missing or bad relay cause this and if so, does anybody know which one. I've been through my owners manual several times and cannot determine which one it would be. Any and all help is greatly appreciated!

bill

 

I blew the #42 fuse, when i replaced it, I still don't have parking lights on my trailer, i also checked the 201 relay, #36, 105,106, I still need to check the 202 fog lamp relay that is the top left relay in your diagram & I don't see how that could be it, is there another fuse I'm missing, maybe under the hood that could help with this, I don't have my owners manual for my 2005 f150. I did check the trailer with another truck and all the lights worked. IT WAS # 10

 

I have fuse box diagram if you need to see it. I put them on my pics, couldn' t put them on this page??????
all the help was great but ------ I needed 2005 f150, all the diagrams could have helped, but only showed part of the problem. There was more then one fuse, and a couple of relays, relays don't go bad vary often, the fuses are seperated for the toe package, and for each function. all the highlighted areas really messed me up because It kept me looking in the wrong areas. so I copied the whole owners manual, found the pages that were for the fuses and box, created a folder on my profile dedicated to jst that if anyone else needs it, but couldn't give the pictures to this post. Thanks for all your help though. I would really love to put together something more helpful here on this site, This is the greatest.

 

Well my 99 has both relays, but no 12v to the 7 pin harness. Oh boy here we go

 

If your having problems with fuses, stop in to NAPA and get the resettable relays. I picked a few up when I started towing other trailers with my '05 and it has been a godsend. They trip if there is a problem, but reset once power is turned off after disconnecting the problem child. I did have to trim the retainer strips inside the cover as the breakers are longer than the standard fuses.

And yes the trailer feed fuses are totally separate from the vehicle fuses. If you blow the vehicle fuses you won't have power to the relays that trip the trailer circuit, but problems with the trailer circuit won't take down your vehicle lights. If I remember right I had to put in three breakers to handle the trailer feeds in the in cab panel. I did not do anything with the under hood fuses as my problems were generally with the the signals and marker lights not the +12VDC or brake circuits. Don't remember if I did anything with the BU circuit.

 

Are there any fuses in the cab for the 12v battery charge for the trailer? Because i checked the fuse under the hood, and it didnt appear to be popped.

 

Don't recall.

If you have a question on the wiring diagram go down to the dealership and look at the wiring diagrams. They don't like to admit it but they are supposed to let you look at them if they are asked. I just made copies of the pages I needed.

The service writer wouldn't let me look the first time I stopped in so I asked for the service manager to come right out on the on the write up lanes and asked him in front of other customers if there was some reason I couldn't look at the wiring diagrams for a vehicle that was no longer under warranty. He stopped for a moment and then told the service writer to let me look at whatever manuals I wanted.

Funny how the will give the responsible answer when other paying customers are around !!!

 

The owner's manual has a detailed fuse chart. The only way to tell if a fuse is definitely good is with a meter.

 

I'm assuming you know how to check a fuse in place, but I'll give a refresher.

With power to the circuit, meter or test light will show power across the circuit ONLY WITH A BLOW FUSE. This is across the fuse not to ground or power.

Good thing about this test is that it doesn't matter if the circuit is switched power or switched ground.

 

Solved my problem...!