2002 Ford F-150 truck problem

There's two things to look at. The first is that switch is adjustable, and it may be out of adjustment. Second, look at the old switch for signs of overheated or blackened terminals, and look at the electrical connector for signs of melting. If a pair of contacts overheated, that usually migrates about 4" down those two wires, and they could get hot enough to melt the insulation. That could allow two wires to touch intermittently.

Yup, but that doesn't mean the switch was in any specific position. I can't remember for sure, but as I recall, that switch is only spring-loaded to come out of the "crank" position. Other than that, you can't really say which position it's in when you install it. Regardless, try loosening the two screws and sliding the switch up and down a little.

Hi,

Is your vehicle the same year, make, and model? I just read through the thread you referred to and don't feel it is a switch-related issue. For the starter to engage, there has to be power supplied to the smaller wire on the starter motor. For that to happen, it has to go through a relay that depends on two different power supplies to function.

I attached a copy of the starting system wiring schematic for your review. Note the relay in pic 2 and its location. Check it and make sure there is nothing loose, any evidence of wires shorting, or damaged in any way.

I will watch for your reply. Also, please confirm this is the same year, make, and model vehicle as well as exactly what you are experiencing.

Take care,

Joe

See pics below.

Hi,

Check the relay in the rear of the engine compartment. For that to happen, power is going where it shouldn't. Make certain that the wiring at the relay is in good condition, nothing is touching, and there is no evidence of damage.

If you plan to replace it, I have attached the directions below.

I'm not saying it isn't an issue with the ignition switch, but most times it is related to the relay.

Let me know what you find or what I can do to help.

Take care,

Joe

See pics below.

Hi,

You are very welcome. I'm near Pittsburgh, so we aren't too far apart. We are expecting Thursday into Friday. Ugh! It's time to move south.

Take care,

Joe

Before you continue, here's two things to check so they don't get overlooked. Check if the two screws are loose that hold the ignition switch to the steering column. The first drawing shows them. These used to be 5/16" hex heads but they might have different heads now.

Second, it's fairly common to find a pair of badly overheated connector terminals or internal switch contacts. Overheating from either one will migrate to the other, so both must be addressed to prevent repeat failures. This isn't likely to happen to the starter contacts within the switch assembly because the current isn't very high and doesn't last very long. However, the part of the switch that turns the heater fan, power windows, and / or radio on and off can have a lot of current flowing for long periods. Once heat begins to build up in the connector terminals, it will harden the wires up to four inches away from the connector. Solder won't adhere to those hardened sections. The wires can get hot enough to melt the insulation and cause two or more wires to touch. This happened at the bulkhead connector on my '72 Dodge Challenger years ago. Walking past the car after it had been off for many hours, I found the radio playing. Turning the ignition switch on, then back off stopped the radio for a little while, then it started back up again. Turns out turning the ignition switch on allowed current to the radio to flow where it was supposed to flow, and let the shorted wires cool down enough that they contracted and didn't pass enough current for the radio to work, (for a little while). Temporary repair was to just separate the wires by a fraction of an inch. Later, the terminals in the bulkhead connector needed to be replaced too. That circuit also fed the heater fan motor. One of the clues was with the ignition switch off, the radio would stop playing when I turned the heater fan on. The shorted wires weren't touching well enough to pass that much current so voltage dropped and the radio quit. Later, I could feel the wire getting hot when running the heater fan, but not after replacing the terminals.

You may find a clue to this by turning the ignition switch to "Run", then when the starter is cranking, wiggle wires on the switch connector. If that seems to have some effect, remove the connector and look for two or more black or darkened terminals, and the connector body will be melted around them. If you see that, the switch must be replaced because the corresponding contacts will have also been overheated. That will cause heat to build up again and damage the new terminals.

Cut the two terminals out of the connector body, then replace them with a pair of universal crimp-type terminals. I also solder them for the best connection. You'll also need to cut away four inches of those two wires and splice in new pieces of the same diameter. Solder those splices and seal them with heat-shrink tubing. Plug in the connector, then plug in the two new terminals individually. These overheated terminals seem to occur more often to owners who are in the habit of turning the ignition switch on and off while the heater fan switch is set to one of its higher speeds. That causes a lot of arcing in the ignition switch. The pitting causes resistance, and resistance causes heat.

Relays are just about impossible to damage, so don't think that way. I suspect, as with my Challenger, by unplugging it or by moving things around, the defect goes away temporarily. In fact, it is your description of the problem that made me think of the radio problem I had. In my story, if I had replaced the ignition switch and tried it, everything also would have worked properly, as it did for you, but that's not because my switch was defective; it's because turning the switch on bypassed the cause of the problem and let the melted wires cool down. The problem came back repeatedly after about an hour.

I have to step back and qualify my comment about damaging relays. This doesn't apply to the newer plug-in relays. If you have Ford's older design with the two large copper studs, those can be damaged if they're left turned on too long, as in more than a minute non-stop. That will warp the coil of wire and cause the plunger to stick. You may get smoke out of it too. Most likely it won't engage, but it is also possible it will fail to disengage.

If the cause of this problem is related to the ignition switch as I suspect, one step in proving that would be, ... Next time the engine cranks on its own when you aren't turning the ignition switch to "crank", go under the hood and unplug the starter relay or, if you have the larger "starter solenoid", unplug the small tan / red wire. If the solenoid (relay) is indeed sticking, the starter will continue cranking the engine.

Both types of relays are listed for your model, but according to this diagram, you have the large solenoid mounted on the inner fender near the battery. That can be damaged, as I described, but only because some other defect caused it to stay engaged too long.

Hi,

I noticed it has been a couple of days since you have been contacted. I was just wondering if you made any progress, and if I can help in any way.

Let me know.

Joe

Hi,

I did notice that but the switch being new and doing the same thing leads me in other directions. However, he certainly could be 100% correct.

Let me know how things turn out for you or if I can help in any way.

Joe

Good afternoon,

Just to throw in my two cents, it sounds like either the relay is bad, or the ECM is grounding the control side of the relay when it should not.

Roy