This is weird. Truck only starts with headlights on. - Hot Rod Forum : Hotrodders Bulletin Board
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Old 09-08-2010, 02:36 AM
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This is weird. Truck only starts with headlights on.

I have never seen this one before... I just bought a '82 Chevy pickup, and it runs great, everything seems to be in good working order, but for some reason, the starter will not crank unless the headlight switch is pulled out at least enough to turn on the parking lights. Once the engine starts, I can turn off the headlights, and it continues running. I have replaced the ignition switch, and in fact tried three different ignition switches, with the same result. (I just happened to have a few laying around). This does not make sense. If I understand correctly, the ignition switch gets all its power from one pin. So if the ignition switch is receiving power from the headlight switch, then why does the ignition coil continue working if the headlights are turned off?? Could this be some bizarre-o relay interlock setup? The wiring doesn't look too hacked, especially for an old, used and abused pickup.

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Old 09-08-2010, 06:49 AM
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Quote:
Originally Posted by SeeTen
I have never seen this one before... I just bought a '82 Chevy pickup, and it runs great, everything seems to be in good working order, but for some reason, the starter will not crank unless the headlight switch is pulled out at least enough to turn on the parking lights. Once the engine starts, I can turn off the headlights, and it continues running. I have replaced the ignition switch, and in fact tried three different ignition switches, with the same result. (I just happened to have a few laying around). This does not make sense. If I understand correctly, the ignition switch gets all its power from one pin. So if the ignition switch is receiving power from the headlight switch, then why does the ignition coil continue working if the headlights are turned off?? Could this be some bizarre-o relay interlock setup? The wiring doesn't look too hacked, especially for an old, used and abused pickup.
I seem to remember a vehicle that was traded to a dealership that I worked at was wired that way intentionally to deter theft , the head light switch was wired to the ignition start (only),but if I remember correctly it was wired to a relay.......turn the head lights on ....it closed a relay that was hooked in series with power to the starter solenoid.
When you do find whats wrong post back...like to know what you find. I have found some weird stuff over the years that I worked automotive electrical...like turn the right turn signal on and the radio cuts on and off with the turn signal.....was a feed back tru a miss wired ground......
Good Luck!!
Kenny
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Old 09-08-2010, 11:02 AM
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Quote:
Originally Posted by SeeTen
I have never seen this one before... I just bought a '82 Chevy pickup, and it runs great, everything seems to be in good working order, but for some reason, the starter will not crank unless the headlight switch is pulled out at least enough to turn on the parking lights. Once the engine starts, I can turn off the headlights, and it continues running. I have replaced the ignition switch, and in fact tried three different ignition switches, with the same result. (I just happened to have a few laying around). This does not make sense. If I understand correctly, the ignition switch gets all its power from one pin. So if the ignition switch is receiving power from the headlight switch, then why does the ignition coil continue working if the headlights are turned off?? Could this be some bizarre-o relay interlock setup? The wiring doesn't look too hacked, especially for an old, used and abused pickup.
There is no factory connection between the headlight switch and the ignition switch, so someone has installed a pretty cool anti-theft device. Either that, or they had a problem with the +12v source for the starter circuit and tapped into the light feed by mistake.

Also, the ignition circuit is separate from the starter circuit.
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Old 09-08-2010, 11:15 AM
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I had 20 vans on the road in my business when i sold out, i had alarm deal put in every one of them,some wouldnt start unless foot on brake pedal,others headlights on, others radio on, this alarm system also encompassed a remote deal to turn alrm on n off ,when on nothing electrical would work xcept alarm.
All of them had a hidden switch under the dash to by pass alarm in case you lost remote,look for a switch somewhere under the dash,should be easy to get to but hard to find.
I also had all glass acid etched with s/n s
I hope this helps!
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Old 09-08-2010, 11:51 AM
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Starts with Headlights only---

Just would like to ask that you post, your remedy, If you find whats wrong or different about your start circuit--I used to find burnt insulation behind fuse boxes, that caused all kinds or stange occurrences--
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Old 09-09-2010, 01:36 AM
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Breakthrough!

Wow, you guys sure jumped on this one fast. And with actual useful information! I knew this would be a good forum to join. Anywho, after reading your replies and surfing through other threads in the electrical section, went out to tinker with the truck some more and discovered that yes, indeed, there is a rather complicated relay system linking the headlight switch, neutral safety switch, and starter solenoid feed from the ignition switch in some weird three-way "and" gate that only allows the starter to crank if the truck is in neutral and the headlights are on. Not a very clever anti-theft measure, imho. A clever thief would no doubt notice if you flicked the headlights on every time you started the truck! So, my remedy to all this nonsense was to run a wire directly from my ignition switch to the starter solenoid, bypassing the neutral safety switch and headlight relay thingy. So the truck will now crank even if it's in gear. I never really cared for neutral safety switches, anyway. Truck runs like a champ, and starts right up the way I think it should. Thanks so much for all the advice!
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