All power is lost after turning key will not start have good bat starter and alt power comes back if bat un hooked and reset

Use a Delco SI 15 self exciting 100amp alternator....Run one 12 gauge wire from the positive terminal on the back of the alternator, to the positive terminal on the starter solenoid, piggy backed with the positive Battery wire.....All power for any additional functions should pick up power at the starter terminal.....All additional circuits should be fused as well......Always disconnect negative battery cable when working with circuits to avoid arcing and damage to diodes in the alternator............

Inlinefuse from batt tu startr cud bbad or put key in on position for tenmin then try startn..may reset theft

If the battery is good you will need to follow flow. Test light is the easiest to use. First hook light to ground and touch pos terminal,lights good next touch pos battery cable end, lights good. Next follow pos cable to starter pos terminal,lights good. Next hook test light to bat pos teminal,touch neg terminal,lights good. Then touch engine block, lights good ground. Next move test light clamp back to ground/neg side and touch alt pos terminal,lights good.if all that tests good, if all good move inside and check for power at ign switch pos term if at any time you dont find power you have wiring issue that needs to be addressed. Let me know what you find. Russ

un hook bat. wate 15 min. well reset but well come back on if not fixed

THIS ALL DEPENDS ARE YOU GETTING A RAPID CLICKING NOISE OR JUST ONE CLICK WHEN YOU TURN THE KEY OR TOTALLY NOTHING AT ALL MOST LIKELY THE POWER DISTRIBUTION BOX CABLE CONNECTOR IS DIRTY OR CORRODED AND NEEDS TO BE CLEANED IT ALSO COULD BE YOUR BATTERY CABLES EVENTHOUGH THERE'S POWER AND THE HORN AND LIGHTS WORK THERE MIGHT NOT BE ENOUGH VOLTAGE FOR THE STARTER TO (A)CRANK (B) THE STARTER ITSELF CAN BE GONE BUT IT'S BEST TO TRY THE THINGS I'VE LISTED FIRST ELECTRICAL CLEANING ALL CONNECTORS RELATED TO THE BATTERY STARTER AND POWER DISTRIBUTION BOX THEN LET THE BATTERY CHARGE UP HOOKED UP FOR 15 MINUTES DO NOT TURN THE KEY JUST LET IT TAKE THE POWER THEN UN HOOK THE CABLES AND TRY TO START IT THIS IS BECAUSE YOU WILL BLOW OUT THE ALTENATORS IN BOTH CARS EVEN IF THERE'S A FRAME GROUND FROM TO MUCH RACING THE ENGINE IF THE GROUND SHOULD COME LOOSE /OLD CABLES NOW THERE'S GOING TO BE TO CARS BROKE DOWN INSTEAD OF ONE GOOD LUCK STEPHEN

Turn the headlights on and watch them while the key is turned to start. If the lights go out, one of your cables or connections at battery or starter is not good. If lights dim a lot but stay on, possibly a bad starter, it needs testing. If lights aren't affected by cranking position, turn lights off, pull the small wire off the starter solenoid, hook up a test light to ground and to the solenoid wire. Light should come on when key is held in crank. If it does, likely a bad starter solenoid. If no light, then the start circuit from ignition switch to starter solenoid is not working. Check for power out of ignition switch on the start wire with key in crank, to begin with. If powered, switch is good, need to check if neutral safety switch is good, and then check or swap in a new starter relay.
Post back with any results.
Good luck.

Local your spare key (2nd key) and try again.


Inspect your key's VAT2 resistor (on the key itself)

SEE SAMPLE pictures HERE

The resistor on the key can come off or wear out.

Pass a vecuum over the key hole and clean the general area with a clean cloth.

I would start at the positive terminal on the battery. Is there a separate wire to the clamp carrying the current from the alternator? It should have a fusible link in it (may not be obvious, could be just a thick spot in the wire). If the problem is not there, you will need to trace that wire forward, checking for voltage everywhere the wire is visible (poke a sewing pin through the insulation to get voltage reading)..

If the theft light on the dash is blinking fast, that would be an indication of the PATS ( Passive AntiTheft System ) immobilizer not allowing the truck to start.

Turn the key from off to run ( do not start ), does the LED on the dash stop blinking ( takes ~4 seconds ) ?

If the LED goes out, and you turn the key and nothing happens, next to check is :
1. The Battery cables: Make sure the battery connections to the battery, and the starter are clean, and no damage.
2. The Starter solenoid fuse : This is fuse #101, 30A. This powers the normally open contacts on the starter relay.
3. The starter relay : This is in the fuse panel in the cab of the truck. If you want to try another relay, you can use the high beam relay or the trailer tow battery charge relay ( both Full size ISO relays ).

One other thing to try, turn the key to the run position ( do not start ) press and hold the brake, and shift into Neutral then turn the key to the start position. Could be the DTR ( Digital Transmission Range ) sensor it corroded in the park position, and not allowing power to come from the key to the starter relay.
If it starts, shift through the gear selector a few times, to see if this cleans the DTR contacts, put back in park shut off, and try to start again.
Here is the starting system diagram, so you can see what I am talking about

Low voltage to solenoid. Try cleaning your bat cables ends inside where they attach to battery , if you're sure battery is good. terms should be shiny where they touch battery terms.