Lil help with dome tappin

[sleestak]

I am in the process of installing cathodes up under the dash. I am hooking them up with a relay, so they act as the dome lights do...unlock car, open door, turn on dome and cathodes go on.

Everything is wired up similar to this diagram Foci_Fosho did in a post by Jabber (link 2 post):




My problem is I cant find the right spot to tap on the dome light to trip the relay. Anyone pull this one off already? I tried measuring with a multimeter and only ended up a lil confused, lol.



sorry for the crappy phone pic...

#1/#2 - Never has power on meter, lights on or off
#3 - Always shows power, lights on or off
#4 & #5 - I thought these looked promising, but no dice.


I am about out of ideas here....anyone pull this off? [???]

[sleestak]

oh c'mon...all these people on this board and no one has a clue? I thought you people knew your stuff, lol

[SangriaS2]

IIRC, there's something counter-intuitive about the "on/off/door" switch on the light itself. I can't double-check it right now, but maybe try changing the switch position & see if you get a different result.

[DisrupTer911]

the trigger for when you open teh door and the dome light comes on is in the door jam, just tap into that wiring

[sleestak]

^^ Thats what my recent thought was...thanks Disrupter. SangriaS2 is right, "counter intuitive" is spot on, lol....whatta crazy set up they have in that dome.

Thanks for the replies guys, i will post up when i give it a go and let you know how it works out.

[Broke_Two_Foci]

the dome light uses a switched ground to turn on and off. the 12 volt source is constant. that is why nothing seems to test right.

[sleestak]

^^ YES!! I just realized this today while looking at a schematic (which is pretty nutty lookin BTW).

I ran around with the tester today and realized that one side of the light has power whenever the light is OFF and then tests no power when the light is ON. (I know, it doesnt sound right, but trust me on this one)

SO, I am thinking, if there is a way to have a relay that is activated with POWER OFF, I would be set. Do they make such a thing? Power goes off and switch gets activated?

[Under_rated]

Originally Posted by sleestak

^^ YES!! I just realized this today while looking at a schematic (which is pretty nutty lookin BTW).

I ran around with the tester today and realized that one side of the light has power whenever the light is OFF and then tests no power when the light is ON. (I know, it doesnt sound right, but trust me on this one)

SO, I am thinking, if there is a way to have a relay that is activated with POWER OFF, I would be set. Do they make such a thing? Power goes off and switch gets activated?

You would have to route power through the relay so that it energizes the coil... and then you want to find the normally open, contact and run power to it and you connection on the other side...

That way when power is off, the connection is closed and when power is on the connection is open.

You have to understad how relays work, when the power is to the coil, meaning you have 12v to pin one and ground at pin 12 thats typical setup for a relay.

Then you have the other pins, and you have to figure out which ones are normally open and normally closed... TYPICALLY the ones normally closed, are the ones on the ground side of the coil...

Take a picture of the schematic of the relay if you need more help and I can tell you what you need to connect where...

Nomally open and normally closed are to be understood that the coil is not energized.

[Under_rated]

I would wire the power for the Coil to 12v and wire the ground to the shifting grounds though you might have to use 2 relays to keep the circuits seperate.

[sleestak]

I understand the basics of the relay...heres the schematic from the package:




86 - is grounded to screw on fuse box corner
87 (12v out) - goes to cathodes
87 (12v in) - goes to horn fuse (always powered)
86 (on/off switch) - should theoretically go with dome light.

Thats what gets me...




#1 - Never has power on meter, lights on or off/door open or closed
#2 - Only has power with door closed and the dome in the "door" position
#3 - Always shows power, lights on or off/doors open or closed
#4 - Always shows power
now this is the kicker
#5 - Always is hot EXCEPT for when the light goes on - then the multimeter shows no power, lol

Here is an electrical schematic of interior lights & such:





this is why I am thinking that figuring out a way to trip the relay when #5 powers OFF, it would be the cleanest way with the exact results I want


hope this helps

thanks for the help

[SangriaS2]

Someone correct me if I'm wrong...

Connect the relay terminal marked "On/Off Switch" to the orange/blue wire of the dome light.

Connect the relay terminal marked "Ground" to the side of the switch that connects to the main bulb.

This should put the cathodes in sync with the dome light.

Hope this helps.

-Joel

[sleestak]

#3 - Black blue wire always shows power on Multimeter

Both my roomate and I have stared at this diagram and the dome light for quite a while now and everytime you think you have something, the multimeter says no. Crazy crazy web of confusion they got here.

The only thing that I have noticed that would get the job done, is to tap the #5 spot on the dome (see pic & explanation above)

[sleestak]

thanks all for chiming in on this...ideas are good.

Still want to know if they make a relay that toggles the power on when the switch is OFF. That would be the final piece to the puzzle

[SangriaS2]

Guess I took too long to fix my last statement.

I'm getting confused now, too. I would think that since the orange/blue wire is the hot side, the other side of the bulb should be a switched ground. Just for curiosity, where are you connecting the meter when you say that the black/blue wire has power?

BTW, the relay you're looking for is a "normally closed" type, which means the contact is closed ("on") when the coil is not powered.

[sleestak]

Originally Posted by SangriaS2

Guess I took too long to fix my last statement.

I'm getting confused now, too. I would think that since the orange/blue wire is the hot side, the other side of the bulb should be a switched ground. Just for curiosity, where are you connecting the meter when you say that the black/blue wire has power?

BTW, the relay you're looking for is a "normally closed" type, which means the contact is closed ("on") when the coil is not powered.

Awesome, I will track down one of those relays and that should make everything work the way i want it to.

Glad I am not the only one getting confused here. When i was using the multimeter, I grounded to the metal box around the fuse box and then used the other stick to probe around and test all the connections on the dome with door open/closed and all switch settings. The idea that there is power going through that bulb without it lighting up baffles me.

Testing either side of the bulb connections with the light off showed power on BOTH sides, lol....once the light was on there was only power on one side. Talk about some crackheaded stuff.

But glad to hear they make a relay like that cause that should most def. get me where i want to me. Thanks. I will post up later once i give it a go....

[SangriaS2]

Glad I can be of some help. I may actually have 5 minutes to take mine apart tonight & see if I can un-confuse myself.

[sleestak]

Well, I think I found the right relay for the job....I am getting close I can feel it.

Here is the diagram of the new relay I bought:




so this is what I am thinking:

30 - Power Supply
85 - Ground
86 - Dome tap #5
87a - Left open
87 - Cathodes

Remember that Dome tap #5 always has power till the light goes on. So, when the light does go on, #5 tap will loose power, the swtich will go to 87 and power my cathodes under the dash. Thus acheiving the end goal.

I will give this a go later tonight and will hopefully post back...maybe even with a How to(?)

FTW !!

[SangriaS2]

Any luck with the new relay? Seems like it should work.

I finally had a chance to take mine apart & see exactly what is going on in there. I'll explain if you feel like being bored to death.

[sleestak]

lmao.

I havent had the chance to try it yet...thats on the list for tonight after work. I will post up tonight.

[sleestak]

Last night I wired in the new relay and guess what..... IT WORKED except for one small glitch

Remember that I am switching the cathodes on when the #5 tap on dome is off....well, after about 20 minutes or so, the car shuts all power off to the dome light...lmao.

I was starting to wire up the lights on drivers side, door open & light switched off....when I hear "click". Look over to the passenger side and sure as *****, the cathodes are on. Thinking this thiung has whooped my @ss

[screwdiver]

Originally Posted by sleestak

Last night I wired in the new relay and guess what..... IT WORKED except for one small glitch

Remember that I am switching the cathodes on when the #5 tap on dome is off....well, after about 20 minutes or so, the car shuts all power off to the dome light...lmao.

I was starting to wire up the lights on drivers side, door open & light switched off....when I hear "click". Look over to the passenger side and sure as *****, the cathodes are on. Thinking this thiung has whooped my @ss

So does this mean when you leave your car the lights go on by themselves? How do you switch the cathodes off?

[sleestak]

yes, they will go on if I leave the car...locked up and all. How do I turn them off? Well I just dont hook them up and consider this project bunked unless someone else feels like enlightening me

[screwdiver]

try tapping into the fuse

[kipp]

what year is your car, i can find locations of the wires for it

[SangriaS2]

Okay, here's "plan b" if you care to try it:

30 - power supply
87a - cathodes
87 - no connection
86 - dome tap #5
85 - dome tap #4




That puts the relay coil in parallel with the dome light...essentially, whatever voltage the dome light gets, the relay coil gets. The only glitch is that the dome light will fade out before the relay shuts off when you close the door.

I had a feeling that the cathodes might end up staying on somehow with the normally-closed contact, but after I re-read the voltages you had measured, I convinced myself that they wouldn't. Sorry about that.