Find the starter relay on an 06Expedition

you may have a short (verify the integrity of the insulation of the positive wire from that fuse going to the rear window defroster, check the relay & switch.) try to replace the relay.

Might be a Short to ground somewhere in the circuit

The problem could be a shorted park netual safety switch . Do you know what a wiring diagram is ? It shows all the componets involved in a electrical circuit ! You IGN.1 fuse 40amp , GM calls it IGN A fuse 40 amp . It feeds the ignition switch and pin 30 at the starter enable relay .When you turn the key to the start position it sends B+ voltage to #8 crank fuse , located in the I/P fuse box ,from there it goes to the park netual safety switch , to pin 86 or 85 of the starter enable relay ! If you pull the relay out of the fuse box an look on the bottom you will see this four set's of numbers ,30,87 & 85 ,86 You can test at the fuse box where the relay plugs in . Here is a video on how to test . The guy presenting the video uses a horn circuit , but it works the same way . It happens a lot , the park netual safety switch shorting out . It may or may not be the problem . VEHICLE RELAYS Operation Diagnosis
Here is a web site for free wiring diagrams
http://www.bbbind.com/free_tsb.html Enter your vehicle info . then under system click on engine , then under subsystem click on starting . Then click on the search button an a link will pop up , click on it .You will see all the componets , connections , wiring colors etc... for the starter circuit for your vehicle .

Do not put a bigger fuse in the slot. If you do, you'll just burn up your wiring harness. A fuse is there to protect the wires. The fuse does this by blowing if the maximum current capacity of the WIRE it's protecting is exceeded. If it's blowing the fuse ONLY when you press the start button, it's in that circuit somewhere. I'd pull the starter relay and try it again. The relay is on the backside of the oil tank. You'll have to take the seat off to get to it. If it blows a fuse then, the problem has to be in the wire that comes from the start button going to the relay. If it does not blow the fuse, buy an new relay and install that. If it starts blowing the fuse again, you'll have to look at the schematic and find out where the wires go and trace them out. If you aren't getting any voltage at the blue wire, pull the relay and do a continuity check from the end of the wire where it plugs onto the starter and the frame. Pull the wire off the terminal on the starter and test it. If you have continuity, you have a short somewhere in that wire. Contact me directly at [email protected] and I'll send you a schematic. Remind me of what you need.

Good Look
Steve

Replace the starter relay in the fuse box behind the glove box. The fuse ONLY powers the control coil portion of the starter relay. If it's blowing, there's a short in the winding or a short between the relay and the theft deterrent module. Bad relay is most likely culprit

your starter relay is defective it is located where the fuse box is located..look for the marked starter relay then replace it with a new one..

It MUST be the starter relay coil - or the power wire that feeds it. Likely a short in the relay coil (AKA starter selenoid).

Possibly three things, either a thermostat problem, starter relay/capictor, or a bad overload protector not closing after an overload. The starter relay should be behind a black box located on the side of the compressor.

Need to look at symntec and see if there is a relay on the starter. Which there most likely is. and it is bad. Look at the fuse and see if there is another wire going from the fuse to a relay,if so replace that relay.

you have a short. maybe in your alarm unit itself try to locate the control box for the alarm and unplug the starter kill relay and bypass it then try starting the car.