96 Ranger 4.0L - Key will not turn off engine

[fighterpilot]

96 Ranger 4.0L - Key will not turn off engine (NOW SOLVED!!!)

94 Ranger 4x4, 4.0L Supercab w/ 5 speed, 204xxx miles.

Issue just started overnite. Changed oil last nite, started it up w/o problems and parked it in the steet. Came out this morning and battery was dead. Put an all day charge on it with negative cable off. Hooked cable back up with key off and noticed the electrical systems came alive and the fuel pump started as if the key was in the run position. Warning lights on dash came alive as well. Truck fired up w/o any problems when I did turn the key. However, the key will not turn the engine off. Disconnecting battery cable will not kill truck. Had to pop clutch in gear to kill engine. When I try to turn the key off with the engine running the voltmeter will drop to zero and all the dash warning lights will come back on but the engine will not die.

Ran diagnostic test on ignition switch and it passed the test. Replaced it anyway along with the key lock cylinder as it was already hosed. Issue remains. I've looked at all of the fuzes in the Power Distribution box as well as inside the cab. I've also swapped some of the relays around in the Distro box. I've cleaned all the grounds I could find as well. Battery is checking at 12.8V but I didn't put it under load.

Numerous Google searches turned up nothing. Some suggestions would be appreciated. Currently sitting with the negative off the battery or it will run down again.

Thanks...

 

[martin]

What happens if you disconnect the connector from the ignition switch?

 

[rangerronny]

I have had this problem before and it was the voltage regulator stuck letting the alternator produce way too much power and i guess the eccessive amperage arced through the switches and relays so everything operated by itself. First and only time i have seen it happen. This was with the engine running so this may not apply to your situation but it may give u another option to check out. Hope this info helps.

 

[fighterpilot]

What happens if you disconnect the connector from the ignition switch?

Truck keeps running

 

[fighterpilot]

I have had this problem before and it was the voltage regulator stuck letting the alternator produce way too much power and i guess the eccessive amperage arced through the switches and relays so everything operated by itself. First and only time i have seen it happen. This was with the engine running so this may not apply to your situation but it may give u another option to check out. Hope this info helps.

Started engine and removed negative cable. Hooked up voltmeter to loose negative cable and positive cable on battery. Alternator output was 14.8V. Seems OK to me.

 

[fighterpilot]

After spending a 1/2 hour or so performing various Google searches I ran across something to try. I tried it and IT WORKED.

The cause of the problem was the FKN HEADLIGHT SWITCH!!!!!

I hooked everything back up and started truck. Turned key off and truck kept running. Turned the headlights on and the engine stopped. Restarted truck and tried again same result. Screwing around turning switch on/off will eventually get truck operation back to normal.

Will go tomorrow and get a new headlight switch. Would never in a million years have thought it was the headlight switch. I've actually been thinking about selling it for a while and getting a new Nissan Frontier 4x4 King Cab. At least if I do now I can get some more trade in since it's back to normal.