Ooooh me so dumb, me fix you long time

[davepl]

So I added a clever little switch that allows me to drive around with the cab and park/marker lights on but no headlights, and turns off with the key, so I don't forget and kill the battery. My dad thought it was wrong to drive with park lights on, and it sounds wrong, but it's really just to run the cab lights without the headlights in the daytime.

I didn't use a diode, so it also means that if you have the switch on you can turn the truck off, throw the key out the window, but it'll still be running because IGN gets power from the park lights! Duh.

Anyhow, there are two easy ways to solve it: a diode or a relay. Anyone a "hardware guy" that cares to comment on which solution I should do (or offer up a third?)

The diode is easy, but because we have such low voltage, you wind up with a lot of amps to run all of the park lights and cab lights. So it's sometimes hard to find a diode rated that high.

The relay is slightly more complicated (IGN powers relay that provides power to switch, but switch can't backfeed power to ignition) and adds complexity, but you don't have to worry about the amperage issue.

Thoughts?

This all started because the PO has a "Park Brake" light in the dash and I forgot to weld up that hole (got the 11 other ones!). So I had a hole to fill and a switch on hand...

[68c10airstream]

Go to a junk yard or accessories installer and get a relay and pigtail harness, about10-15 bucks. Accessories guy should be able to tell you the wiring or look at the relay and pay attention to the numbers at the terminals

#15, or #30 can go to fused battery terminal

#85 goes to ignition "on" signal "+" feed (lights will come on only with the truck running)
#86 goes to ground
#87A goes to load (lights)

#87a is connected to #15 or #30 when the key is turned on, and disconnected when the key is turned off

Not to confuse you but 85 and 86 are the light duty switching circuit to control the heavy load and connect #15-#30 to 87A

['68 Newtricks]

30,87, 87a
85, 86



kinda what airstream said
85 to coil
86 to ground
30 to + battery
87 to running light circuit

but you won't be able to turn them off while engine is running, you will still have control over all lights after the engine is off (key off)

[bhc41051]

I think I'm on your Dads side :-)

[davepl]

Yep I know how to hook up a relay, it's not my first rodeo, but I was wondering if a diode isn't a better idea.

I used a diode once so that the courtesy light above the glovebox on my Pontiac would come on with the doors, but the switch on it would independently light it (and not turn on the dome light). That worked great, but I was worried about the amp load due to our low voltage system.

[VetteVet]

You don't need a relay and you don't need a diode, but you do need something that is switched by a running engine. That would be an oil pressure switch that closes at less than 10lbs of oil pressure. You would have to wire one side of it from an always hot source such as the battery alternator junction or the starter main cable.

The other side would be run to the brown feed wire that powers the cab lights or if you wanted to shut them off while running the engine, you could just run the feed wire to one side of the dash switch you installed, and run the other side to the brown light feed wire.

This way if you shut off the engine the oil pressure switch would kill the power to the lights and even if you left the switch on the lights would go out and the engine wouldn't run on.

If you needed the parking lights you could still turn them on with the HL switch.

You should use 12 gauge wires and run a fuse the same size as the stop/tail lights fuse in the fuse panel.

[lutronjim]

High amp diodes can get very hot.

[Gromit]

I was driving a customer's V12 Jaguar up to a busy intersection and the throttle suddenly stuck open.. but the reason I'm still here to write about it is because the ignition switch worked to kill that beast.. (the old brakes were not enough for that stumpy V12)..

So I'm sure everyone knows but just a reminder the ignition is a nice last resort to be able to depend upon.

(by the way the title to this thread is an instant classic)..

[davepl]

Originally Posted by Gromit

(by the way the title to this thread is an instant classic)..

Thanks... I was starting to wonder if -anyone- got the reference :-) It's FMJ from long ago.

[franken]

Got the ref.
A diode conducts current in one way. A relay is an electrically controlled switch. Not the same.
Pulling the headlight switch out to the 1st on position turns on the park lights. The ignition switch doesn't control the lights, but...

[vics stuff]

I agree with bhc41051. I always drive my vehicles with the headlights on . Always want to make myself visible . Not interested in driving with the parking lights on to look cool. I detest people who drive in my state with parking lights on especially when it starts to get dusk or cloudy. They are just rolling the dice to get hit. The parking lights are for a non moving , running vehicle.
I value my safety and property.
I have come up with a cheap easy to install buzzer relay kit that I have installed in all my older vehicles to notify me when the ignition switch is turned off and the lights are still on.
Works great. Planning to put one on my $70,000.00 32 Ford street rod project.
Vic