Looking for a live wire when car is off...

[ToolGuy]

Hey, I am looking for a live wire when the car is 'off' and that same wire "not live" when the car is 'on'.

Reason: I do not have the temp sensor or twilight sensor, which ever one it is in my dash pad plastic vent. However the hole provision is there for the sensor and I mounted a red flashing LED in the hole.

Now I just need to wire it to a live when the car is off wire.

Can anyone help me with this?


Thanks,

[c4c5specialist]

HI there,
There is no wire that will allow this;
The best way to accomplish what your looking for is to wire a 5 pin relay that is energized when you turn the key on, to stop power to the LED>
Then,when you key off, the relay becomes deenergized and then lights the LED>
Allthebest, c4c5

[ToolGuy]

OK thanks for checking... I will tinker with a relay to get the idea on my work bench. I should be able to hide the relay at the passenger side fuse block too.

[aquaholic]

its called a reverse acting relay. which is really just a relay wired using the normally closed contacts that open when the relay coil is energized instead of the other way around. most relays have 2 sets of contacts. one set normally open and one set normally closed. when you wire your hot to the normally closed set of contacts the relay coil would not be energized when the car is off, thus passing you hot along to whatever you want to use it for. when you turn the car on, the relay coil will engage thus breaking your normally closed set of contacts that the hot wire is wired into it.

[ToolGuy]

Just getting back to this now. OK now I see Aquaholic and understand the concept.

I have a 5 position relay and a 4 if needed.

Could someone guide me through this process?

I know I can do it but never have. From what think of it I need a power and ground wire and then the two wires for the LED. That is where my thinking stops though.

[aquaholic]

what is a five position relay? i'm thinking what you mean is you have a relay with 5 sets of contacts. right. i dont know you so let me go through some relay basics first. the part that actuates the relay (pulls it in or out) is called the coil. the other part of the relay that the wires go to that you want to make or break are called the contacts. the the first thing you will need to do is test the contacts (not the coil) with a multimeter and determine which ones are normally open and which are normally closed. by normally open i mean which contacts are open when the coil is unpowered and by normally closed i mean which sets of contacts are closed when the coil is unpowered. jumping ahead a bit, put the hot wire you want to switch into one of the normally closed contacts and that hot will be passed to wherever you want it to go when the coil is unpowered. then just wire a switched hot to the coil so that when the car is running the coil gets powered and breaks the circuit and when you you shut the car off the coil goes unpowered and your hot wire on the contact side gets passed through. if i'm making this sound to basic for you i appologize, i dont mean to insult your intelligence i just dont know how much you know about electricity. thats all. check this out http://www.kele.com/olcat/RC15/RH-RR_RJ.pdf i use these idecs at work alot. they cost about $8 and have a coil that can be pulled in with 12 volts dc. more importantly than the brand name or price is that the link shows 2, 3 and 4 pole (sets of contacts) relay wiring.

[ToolGuy]

No insult taken, I appreciate the help! This is not my speciality so the more detail the better for an explanation. Yes I mispoke, my relay is a 5 pin. It is from a set of fog lamps I had years ago.

I will take the relay and us my DVOM set to continuity and check for which pins are closed and open then.

So I will need two different power wires? One to close the contacts and one to pass through when the ignition is off?

[aquaholic]

yes. and, i never though youe were reffering to the number of pins so now i understand what you have. since there are 5 pins i would assume this: 2 pins are for the coil. a switched hot and a steady ground. those are what pull the relay in and make the contacts switch from open to closed or vice versa. the other 3 pins would be the common, normally open, normally closed. you would put the hot that you want to pass on the common and continue the wire out to where you want to go on either the normally open or normally closed depending on what you want to happen. the relay should be marked in some fashion to show which terminals are which. check out the link above it shows how some are marked. your relay is the same as the RH1B electrically although it may look diferent.