Ok so id like to wire up some lights for when the doors open they light up and also when i turn the headlights on they come on as well. Im thinking i could tap into the dome light positive wire and the center console bulb(lights up the Hvac plate) wire and use a relay. Im not a wiring expert but im pretty sure this shouldnt be too hard to accomplish. Am i on the right track or is there a much easier way to do this. Thanks any help will be greatly appreciated.

 

Where are you putting these lights?

 

You need diodes, or else your dome light will come on every time you turn on your headlights.

 

i want them to light up the floor boards like most cars these days when you open the doors

 

Just use the existing floor board light wiring and install whatever lights you want..?

 

It can be done with a standard SPDT relay. The relay's coil terminals get wired to ground and to the brown wire on the headlight switch. Terminal 30 on the relay goes to one side of your lights. The other side of the lights gets wired to a constant +12V source like the fuse box or the constant wire for the radio(if your only adding 1 or 2 bulbs). Terminal 87 on the relay gets wired to ground. Terminal 87a on the relay gets wired into the driver's door switch.

If that doesn't make sense, I can draw up a quick diagram.

 

I have done it in my car. You actually need 2 SPST relays.

1st is for the 'open door' circuit - the door switch provides a ground for the interior lights, but the headlight switch provides a power for the operation. Thus, you have to use a relay between the door switch and the lights you are installing, so that when the door is opened, that door circuit is providing the ground for your relay - which already has a full-time power source, and thus the relay activates and sends 12v+ to your lights (which are already grounded).

2nd relay is to interrupt this door circuit power to the headlights - without it you'll be powering the park lights everytime you open the door, since opening the door activates the 1st relay and backfeeds power through to the park lights. So the 2nd relay goes between the headlight switch and your new lights.

Hope that makes sense. When I did mine I came across the problem of park lighyts burning with door open and learned the hard way (the best way to learn anything). The 2nd relay interupts the headlight part of your new light circuit by not letting any connection between the door opening and the headlight switch - the ONLY time there is a connection from the headlight switch to your new lights is when the headlight switch is turned on.

So, in the end, you have scenerio A which is door opens, door switch makes a ground which activates #1 relay that already has 12v+, and the activated relay sends 12v+ to your new lights.

And scenerio B - you turn on headlights, which sends 12v+ to relay #2 which is already grounded, activating it and sending 12v+ to your new lights. BUT - this second relay keeps that circuit interrupted when the headlights are off, so that power from relay #1 is not backfed to your park lights.

There's probably a way to do this with a DPDT relay or something else, but this was simple for an electronicsw idiot like myself and it works.

 

ok thanks for the help guys. imma head to the store tomorrow to get what i need...
Checklist..?
wire
2 bulbs and sockets
and 2spst relays or 1 spdt relay?
thanks for all the help hoping to get this done tomorrow

 

Much simpler to use 2 diodes and no relays.

 

what would i have to do for that? i dont know too much about electrical. what exactly is a diode?

 

A pair of diodes would probably work too, I just never learned how to select the right one for something like this which is why I didn't suggest it. Simply put, a diode is like an electrical check valve. It allows electrical current to flow only one way through a circuit.

Using diodes you would wire them in to keep the door circuit from backfeeding power to the parking lights and turning them on each time you opened the doors. I'm honestly not sure how Apeiron is thinking of wiring them in so you only need 2 of them and no relays. I'm probably just missing something obvious though.

As for which way to do it is up to you. You've got 3 suggestions(with a little clarification from Apeiron) from 3 different members that will work. I'm guessing each of us has suggested the method we did using the components we are most familiar with. The choice of which method to use is yours. I will say that using 2 diodes sounds like it would be the cheapest, simplest, easiest way to do this. And that is what you want with electronics. The simpler the circuit is makes it more likely to work and easier to troubleshoot if it doesn't. Only downside to using diodes is the auto parts stores don't carry them. You would have to go to Radio Shack or somewhere similiar(Fry's maybe?) to get them. They are usually less than a dollar or 2 for a 5 pack.

 

thanks so much for the information and also your idea of how to wire it up. cheap and easy.. exactly what i want. ill see if i can get a little more info from apeiron and ill be good to go. thanks guys

 

Oops, my mistake... the courtesy light switches the ground, should've remembered that.

One SPST relay, one diode, then:



Bulbs are normally unpowered. Turning on the headlight switch puts power on the INST fuse through the dimmer rheostat. Your lights will be dimmed with the **** with rest of the interior and instrument lights. Opening the door or turning on the overhead light energizes the relay, putting full power to the bulbs. This will turn them on if the headlights are off or put them to full brightness if they're already on with the headlights. The diode prevents current from entering the interior lighting circuit and turning on or changing the brightness of the interior lights.

You can do it with a single SPDT relay, too:



The NC contacts are connected to the INST fuse to control the lights as above but when the courtesy lights go on the relay energizes and supplies full power through the NO contacts. The downside is that you get a little flicker when the contacts throw.

 

I didn't know about the INST fuse slot back long ago when I did mine, and I connected into the park light wire from headlight switch. I'm guessing if I had used that INST slot instead the dorr opening would not have backfed power to the park lamps like it did and thus I wouldn't have needed the 2nd relay huh?

 

It works the same way whether you use the park light wire or the INST fuse, just the power from the park light wire won't be dimmed.

 

thanks for the help guys. ill be doing it today. thanks

 

Well, dimming wasn't an issue for me anyway, I used LED's!

 

ok im gonna go with the single spdt relay method. went to radioshack today and there were too many options on spdt relays i had no idea. some had switches, some said spdt mini, some had different amps, so what exactly am i looking to get?

 

I don't see any relays on the RadioShack website that I'd want to use. Go to an auto parts store and ask for a MAF burnoff relay for an 86-89 car with TPI. It'll be more than enough.

 

ok apeiron thanks for all the help will do so tomorrow

 

I simply used whatever 4 prong relay was on the shelf at auto parts store.

 

off topic a little bit but ive done research but cant really find the answer. what color wire is the parking lights and where is it located?

 

I want to say brown. Easiest place to take it from is the back of the switch.

 

ok i just purchased some aftermarket headlights and housing. it has a parking light and the normal headlight. i need to put the parking light wires together and dont know where to do so.

 

Or take it from the wiring at the factory parking lights, then.

 

at the headlight conector?

 

No, one of the marker lights. The headlight connector only has the high and low beam circuits.

 

oh ok. so just tap into one on each side then?

 

That should work.

 

thanks for the help. ill let you know how it turns out.

 

Here's just about every wiring diag available for a 3rd gen: http://www.austinthirdgen.org/index.php?pid=19

 

well the headlights turned out great then to a epic fail!!