I installed a brake controller in my 2005 F150 STX and the final step is installing the relay for the trailer battery charge that goes into the RO5 location in the fuse panel. Question is before I buy the relay from Ford I seem to have and extra relay in he RO4 location which powers rear window defrost, I don't have this option. Has anyone taken it out and moved it over to RO5, and does it ONLY power the defrost? I would hate to inadvertently cause another problem by the pull it out and see method to reuse this relay.

 

You can buy the relay at any auto parts store.. you don't need to get it from Ford. The RO4 relay may be used for other things besides the rear defrost. You can always pull it and install in RO5 and see what don't work.
Just look in your book to see if RO4 and RO5 use the same relay.. there are several that are the same. Not positive on those 2

 

Same relay part number, I went ahead and just pulled the R04 relay and the common 40 amp fuse in slot 114. Moved relay over to RO5 and everything seems to be working just fine.

 

Roger that.. what is not working now ? Anything ?

 

Everything is working properly, as far as I could tell the Relay RO4 only worked rear window defrost and heated mirrors(neither of which I have). I just hate the "pull and see" method, but I didn't have a choice. I stuck it into the RO5 and all trailer functions work also.

 

Sweet

 

Well, of course, the issue was my own error. The connector to the Alternator wasn't clicked all the way in.

Now, after kicking myself for this, I went to get another ice cream cone for finally figuring the power issue out. The Pick a Part battery has been holding up just fine. I'm going to get it tested and charged if needed today.

I replaced some additional bulbs, curtesy lights that face the bed as well as the reverse light in that set of 3.


The 3 prong connector was not making complete contact to the plug.

Reached down into there and pushed that plug until I heard it 'click'.

This one...