i have a 2001 f150 wouldnt start the other day replaced battery still wouldnt start alternator was bad replaced it now when i turn the key all power is killed instantly. Has anyone had this problem is there a anti theft button that got triggered? i have no idea any ideas will be greatly apperciated thanks

 

Dirty or loose connection at battery post terminal or other cable. Or possibly a bad cable. Those would be most likely.

 

no have tested to see if there is power past the inline fuse and over to the fire wall do you know if there is a anti theft switch hidden by the fuses thats where i was told one might be at

 

Power to everything is lost when you try starting ?

What happens if you turn the key from off to run ( do not start ) ?
What happens if you turn the key from off to accessory ?

Antitheft, is there a an aftermarket security system on the truck ( non factory ) ?

The factory antitheft is an immobilizer with the key.
The truck would be a crank no start and the theft light would flash if it is the factory one causing it ( you would still have power ).

What was the symptoms that lead you to replacing the battery and alternator ?

 

sscullly
power to everything is lost off to run it will kill it i havent tryed going to accessory and i do have a aftermarket alarm
just put 4 kc lights on went out the other night to adjust the lights n drive around was out for about 2 hours next morning went out to leave to work and truck was acting like a dead battery tried to jump it but did no good. put battery on charger for the day came home put it in and was toast took it got it replaced still did same thing with a brand new battery tryed alternator still doing same thing.

 

Loss of all power when the key is turned to START is virtually always a defective/discharged battery, battery cable, or battery cable connection.

You're wasting your time looking at anything else until you have proven that all of those things are in good order. That will take a multi-meter and some voltage checks instead of just replacing stuff.

 

OP, just went through the same thing today, as others have stated, you have a connection problem...Try to wiggle around the cables while someone starts it. I also have a brand new batt and alt. I traced mine down to the ground (neg) cable. Pulled it all apart and it looked fine but it did have a short in it. If i moved it around while connected to the battery, it would fire right up and radio, lights etc would work. Before i moved it around, nothing, no power to anything at all. Im putting my guess on a bad cable. Try it out.

 

A cable is supposed to be a "short".

You had an "open".

 

Yea, got them mixed up. Open circuit i meant.

 

i have full power. key to acc no problem. key to run no problem. key to start all power off. heard a click, no starter crank, all lights off radio off, all dead. remove jumper cables and reconnect all power comes on again. turn to start - click (not a high tinney click but a low thud like click) all power off. if there some hidden protection relay???

 

No.

Go back and read (and heed) post #6.

 

Did you ever figure this issue out as mine started doing the exact same thing today.

 

I'm definitely going to have to agree with Raven on this one. It's because of security or anti theft .. auto start connection . Mines doing same thing . Did you ever figure this out raven? Perhaphs I should read till the end of this thread

 

See post # 11.