TBirds

Good afternoon F150 community,

I purchased a 2000 Ford F-150 at an auction recently but I have been having some issues getting the key to work. I replaced all of the fuses in the cab (Haven't done the under the hood fuses yet) but fuse # 21 keeps blowing. The fuse diagram says it's either the Clutch Pedal Position Switch/Starter Interrupt Relay or Digital Transmission Range Sensor. It does have a factory anti-theft device that blinks (on the instrument cluster) all the time (even when the key is out and the truck is off). I already planned to replace the ignition switch and starter solenoid/relay which I have, but the fuse keeps blowing. When I replace the 15 Amp fuse, I'm able to start it with the key 3 or 4 times before the fuse blows (I start them within hours of each other, not consecutively). Could this be caused by another blown fuse under the hood? Ivery read that it could be caused by a short but being inexperienced with vehicle electrical systems and unable to find a decent wiring diagram for the truck, I didn't know where to look. Any ideas on what could be causing this? I appreciate any input.

Thanks in advance,
Timothy (TBirds)

akdoggie

You don't say if you have an automatic or 5 spd. I'm guessing AT, so I'll start there. Check the connector to the neutral safety switch and make sure it is clean and fully plugged in. Check that wiring for possible bare wire etc. If all is ok, then try to start your truck in neutral. Move the lever a bit if it doesn't try and engage to see if the switch is out of position, maybe damaged.

We have a battery saver relay on our trucks but not an interrupt relay. He is a wiring schematic for your truck.

TBirds

Yes you are correct, it is an automatic transmission. I'm looking at the wiring diagram in the PDF you sent (Thanks a lot!). I'm on page 122. When the ignition switch is turned to the run position, all of the accessories and everything turns on just fine, the fuse seems to blow when in the start position. Once the fuse is blown, I can turn the key to the run position and jump the solenoid to start. When the fuse blew last night, I was actually able to see the bright spark when it popped and it was audible. I don't see, on the wiring diagram anything about the neutral control switch. (I'm not disregarding that possibility, just trying to get an understanding for how this system works.) I see on the diagram, the ignition switch goes to the fuse box to fuse 21. That's the one that's blowing. Ideas?

Thanks again,
Tim

TBirds

Oh I see. Checking to see if it blows in neutral kind of tests the DTR?

akdoggie

No. Trying to start it in neutral, will help identify if the NS switch is working or if the switch is possibly defective. Just trying to put you onto the correct path to follow before throwing a bunch of parts at something that it doesn't need, or shouldn't need. Have you tried it in any gear but park? HOLD THE BRAKE, just in case it does engage. You want to keep your garage walls standing. lol

TBirds

Yes I have. It does start in park and neutral, but no other positions. I really appreciate your help by the way.

akdoggie

Starting in park and neutral is correct. No other gears should it start. That is the reason for the Neutral Safety switch.

Now if the truck starts in P and N, then is it working correctly now?

TBirds

That's not quite the issue I'm having. I may have given off the wrong idea. The problem is that when starting the truck, the fuse #21 is blown. Once blown, I can not start the truck with the key until the fuse is replaced. The fuse blows over and over.

akdoggie

You need to check that wiring circuit and see where the short is being created. Maybe a wire is rubbing underneath or under the dash. Something is causing the amperage to exceed your fuse limitations. Follow the circuit from the wiring pdf and see if you can find where it is shorting. It could still be a bad NS switch, but I'd certainly check the wiring first.

TBirds

I will have to check the wiring this weekend. I will come back and let you know! Thank you for all of you help!