I have a 2005 F150 XLT w/ 5.4 engine with only 75k miles. For some time now my radio will suddenly go out for no reason. Then after a few minutes or a few days the radio will come back on. Simultaneously, on occasion my truck will not start. This occurs more often when it is cold. I replaced the starter/solenoid unit to no avail. It is the NOT the battery. It is fully charged and I have no parasitic draw. I did find that when I go to the fuse box and tap the R102 relay which goes to the starter solenoid (or pull it out and put it back in) the truck reliably will start. The same goes for the radio when I do the same thing to the R102 relay which controls the accessory delay. I have replaced both relays and that didn't fix the problem, so bad relays are not the issue.

Recently, the passenger rear brake light doesn't work. I went to have my oil changed and the mechanic told me my signal light was out. When I got home I checked it and it was working fine. The following day, the signal wasn't working.I thought that was strange. So I replaced the bulb and it worked fine......for a day. Shortly after the signal would not work but the bulb and socket works fine when I swapped them into the driver rear signal location.The driver side rear signal works fine. The fuse is not blown (fuse 2).

So here is my question. It just so happens that the fuse 2, and relays R101 and R102 are all adjacent to each other in the fuse box. I'm thinking the fuse box might be bad. If I pick one up on Ebay, it should just be a matter of bolting off and on with no flashing from the Ford garage. Correct? But before I go ahead, does anyone have any other thoughts? Is my thought process rational or are there other avenues that I should investigate?

 

I would check the grounding of the fuses boxes carefully.

 

FYI, the passenger rear stop lamp fuse is F42, not F2. While f2 is in the stop lamp circuit, it would affect more than a single stop lamp if it were not supplying power.

You've pretty much determined that you have one or more intermittent connections somewhere inside the CJB so you've made good progress so far.

Replacing the fuse box is a simple swap, no programming is required. Before committing to that, I' probably pull it out and inspect for any kind of damage (water, vermin, etc) or for loose connections at one of the many plugs. The solution might be as simple as re-seating of connectors.

 

projectSH089, in my manual it says f42 is "trailer tow left turn/stop lamps" and f2 is "stop/turn lamps, speed control deactivate switch" Also, F42 is also located only 2 positions away from F2 so perhaps my fuse box theory is still valid since F42, R101 and R102 are sill in near proximity to one another. However, could it be an ecm issue as some people have suggested to me?

 

error

 

ManualF150, do you mean that cable that comes off the fuse box that screws into the frame? It is a little rusted. Would I just disconnect one of the battery cables (black) and sand it down a bit?

 

Yes, the one the comes off the fuse box that screws to the frame.

 

No. The PCM has nothing to do with either the radio or the turn signals.

The owner's manual "dumbs down" the information for a "typical" owner while I looked at the service manual.

A faulty ground at the fuse box would not take out all three functions simultaneously. In any event, none of the three circuits mentioned use a ground in that vicinity, they use three different points widely separated, none of which are in the vicinity of the fuse box.

 

ManualF150, checking the grounding wires from the fuse box will be my first order of business. I will check back in a day or so. Thanks

 

If the problem was a faulty ground, then one wouldn't expect pushing on components in the fuse box to produce any result. Yet, that is exactly what you've reported.

 

ProjectSH089, just to clarify the no start issue (Relay 101) and the radio cut out (Relay 201) do not happen simultaneously. They are random and only rarely coincide. The passenger rear brake light is a new issue. The car has been well kept so its not a rust bucket with years of abuse. When its cold, i think things contract and the
"likely" short pops up more frequently for the Relay 1010 and 102 issue. Right now the car is starting fine and the radio is working fine since I've been keeping it in the garage. Only the passenger rear brake light is out. BTW, I spoke to the Ford mechanic and he said fuse 42 (for trailer tow rear right turn/stop lamps) is nurelated to the trucks rear right brake light.

 

I stand corrected, I didn't look closely enough at the squiggly lines of the schematic. Sorry about that. However, there are no fuses dedicated to a single brake light although both signals do pass through the CJB so they can be tapped off to feed the fuses for the trailer adapter. Therefore, an intermittent brake light on the truck could be due to an intermittent open circuit inside the CJB as well as from causes external to the CJB. I'd still be inclined to go through the exercise of inspecting the CJB connectors and reseating them if it were my truck.

It would actually be an "open" which is the opposite of a short. Perhaps the relay socket's pins are loose and they're the issue. You might try seeing if you can tighten up the contacts for the relay pins using something along the lines of a dental tool to push the contacts back towards the center of the slot. If you do, be sure to disconnect the battery first.

 

projectSHO89, in my methodical plan to solve my problem I am proceeding cautiously....only altering 1 variable at I time. Today its 26 degrees out. My car would not start. As usual the instrument cluster would light up but no sound when trying to start. It's was as if I wasn't even turning the key in the ignition. When the car did not start (R101 relay) the radio would play (relay R102). I had to tap the relay twice to get the car to start. I pulled the relays and they seemed to have a film on the prongs so I lightly sanded them and placed them back into the fuse box. Car started and the radio worked. I went for a brief 5 mile spin and experienced no radio turning off on its own. I will test again tomorrow when the car is cold to see if I have the same luck.
Meanwhile, the rear passenger blinker is not working, However the front passenger blinker works fine. When its dark and the car's lights are on, the bulb does light up. I believe there are 3 wires to the turn signal socket. I assume one wire is the hot for the nightime lighting, one is for the turn signal and one is the common return..Correct? I will try to isolate which wire is the hot for the turn signal and try to see if the wire has a short near the light socket.
Thanks for working with me on this.

 

Yes. Off the top of my head, the black one would be ground, the brown one would be the running lamp, and the other one is the turn/stop lamp. If those colors don;t match what you have, let me know and I'll look at the schematic.

 

The right rear blinker is not working - what about the right stoplight?