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Guest Message by DevFuse
 

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So you want to wire a relay??? Starter, lighting, WHATEVER.


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24 replies to this topic

#1 daeron

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Posted 13 April 2007 - 06:47 PM

I have been threatening to get around to this for some time, now. Well, I am doing it.. the tell-all expose on how to install a relay into your car for whatever circuit you want: Starter solenoid control, add foglights, radiator fan, fuel pump (although bypassing stock fuel pump wiring on a fuel injected vehicle is a BIG no-no...) WHATEVER.

First, go to the junkyard and find a late 80's BMW 3-series. Many BMWs (and other European cars) will have a single plug, and the relays needed, but the box I show here was sourced from the BMW I mentioned.

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The relays

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The Full relay BOX (optional, I got it because I have ALOT of wiring to re do on my Datsun) These plugs are found on many vehicles, and slide off this bracket easily to either re configure, or use singly (as I did for my starter relay)
Posted Image

The relay box can take up to five relays in total, and the plugs can easily be slid off and moved around.

In order to get properly sized wires for my application, I used a tiny "precision" flathead screwdriver (eyeglass size, or nearly) and reached down from the top of the plug, on the bottom of the "U" formed by the female spade terminal. Then you bend down the little retainer clip, and the wire slides out. I cut a handy selection of wires out of the cars in the boneyard so that I can configure them any way I wanted.

Some of the relays are rated in amps on the packaging of the relay itself; others are not, but you can generally assume 30 amps or better from what I can see. To be safest, find one that says right on it "30 amp" or "40 amp" If you are unsure what amperage you need, easy math. voltage x amperage = wattage.. so if you are wiring a pair of 55 watt fog lights, thats 110 watts. 110W/12V=~9.2Amps I used a 30 amp relay for my starter circuit and haven't had any problems. It IS best to have a couple of spare relays in the glovebox at all times once you do this conversion... As far as "too big," I am fairly certain that isnt possible. Besides, you can always limit the current flowing through the circuit by installing a smaller fuse in the high-current supply line from the battery to the relay's terminal 30.

I originally did this for my starter; I was turning the key and getting a *click*click* but no start. For some time I was using a screwdriver to bridge between the battery cable and the solenoid terminal with the key "on" to start it. I wound up installing the relay to do the job of the screwdriver.

This is a simple task, but first you must understand how the relay works. (If you already know, skip this paragraph) It is NOT anything to be intimidated by.. I have heard people make comments to the effect of not wanting to "complicate" things by using a relay.. relays SIMPLIFY things. The relay is a high current switch, with at least four terminals on the bottom. One terminal gets fused 12VDC+, either straight off the battery or from some switched source. Another terminal (or two) goes to your "load" (starter solenoid terminal, pair of foglights, fan.) One terminal gets grounded, so the relay can function. The final terminal is the "signal" terminal, and that goes to your "switch". One VERY common example of a relayed circuit that alot of you folks would be more familiar with, is in your car Amplifier. Most modern stereos have a blue wire coming out of the back of them; you are supposed to use this blue wire to turn your amp on. But wait, this blue wire does not POWER the amp; thats what that huge cable with the gold fuse that cost so much money was for, right?! The Blue Wire activates a relay inside the amplifier.. so that when you turn the stereo on, the blue wire gets voltage, sends it back to the signal terminal on the internal relay of the amp, (trust me, there is one there) and it turns on. Make more sense now??

If you are using this for a lighting circuit, then you could just tap into say, the running lights + circuit I THINK, but I know the headlights have a CONSTANT positive battery voltage connection, and the switching is done on the ground circuit.. so if you were to tap into the headlight positive circuit for your "signal wire," then your relay would always be on. You could certainly switch ground to the relay, and give the relay constant positive voltage (fused of course) if you wanted to turn your foglights on with low beams only, say.

For the purposes of the starter conversion, I used the original solenoid wire as my signal wire. The relay requires a miniscule amount of current to operate, so even if your ignition switch can no longer handle the current needed to activate the solenoid, it will still run the relay if the wiring is intact at ALL.

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This is a diagram that I made on how to wire the relay up for a starter circuit. Skip made a much better one, but I cannot find it right now. (Skip, feel free to respond with your diagram. Please. :-p)

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This is what the relay looks like as installed in my engine bay. I secured the relay to the spare tire support bar, and grounded it there as well. Note the inline fuse (its the bottom one) for the power supply to the relay.

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This is what it looks like underneath. Again, note the inline fuse underneath my grubby paw, and the new red wire going to the starter solenoid in the bottom right corner.

So now, when I turn my key from "on" to "start," instead of sending fairly high current through the ignition switch and into the solenoid terminal to engage the solenoid, the ignition switch just sends low current to the relay. The relay then does the job of switching high current, obtained directly from the battery through new wiring, straight to the starter solenoid.

Now, this same concept can be applied to ANYthing, and you can use the same relays and plugs. Again, these relays can be sourced out of MANY MANY European, Japanese, and Domestic vehicles.. not just BMWs. Some Volvos, Jaguars, Mercedes, Volkswagens, Audis.. NOT difficult to find.

Recently another board member was trying to figure out how to wire in his fog lights from an XT6. I drew him a diagram on one way to do this, using a five-pronged relay (the fifth prong is a second "output") and using the running light power as a signal, thus turning the fog lights on whenever the running lights were on... but NOT drawing power off of the same circuit! The ONLY power drawn off of the running light circuit is the power needed to turn and hold the relay "on," less than 0.1 amps. (any better figure on amperage draw for one of these relays?)

Posted Image

Now, in the two diagrams that I have posted, I inadvertently transposed terminals 85 and 86; these are the ground and signal terminal that operate the relay. This does NOT, to my knowledge, make a difference; the important thing is that the relay "control circuit" has one signal wire and one ground wire. (Again, anyone want to correct me??) In order to run fog lights off of a switch, rather than piggybacked onto your running lights, all you would need to do is install the switch in your cabin, find a source to supply the switch with 12VDC+, and run a wire out of the switch up to the relay signal terminal.

Now, electric fans are usually turned on at a certain threshold temperature... and electric fuel pumps, in a fuel injected vehicle, are already run by a relay, but that relay is controlled by the ECU. However, this relay information can be used, along with a little brain power, to relay ANY circuit on ANY car, ANY time. Some situations, bypassing stock wiring is bad. (read: FI fuel pump) However, this info can also be used to install new relays and wiring for dim headlights. I will say here and now that the headlights on my 87 GL-10, when well adjusted are EXCELLENT so, if youre headlights are too dim, chances are it is a wiring issue. Sure, installing some brighter bulbs will give you more light.. but re wiring is a better option.


This should help clear up some confusion; and by all means, feel free to link to this write up for any reason; also, if you have questions feel free to contact me vie PM here on the board. It is FAR from Subaru-specific (outside of the headlight wiring info) and in fact, I was using the Soob as a test mule for work needing to be done on the Z-car. Plus, this sure beats using a screwdriver to start your car!!!! :lol:


#2 daeron

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Posted 13 April 2007 - 06:49 PM

USRM worthy?? all questions in red I would appreciate answers to, so that I can correct as needed, and edit them out.

Like I said, I have been meaning to get around to doing this for a while.

#3 Phizinza

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Posted 13 April 2007 - 08:39 PM

Nice to see some knowledge sharing.. I've just been reading on an Australian Subaru forum and no one wants to give away their experience it seems.. I love this forum.
:headbang:

#4 Mykeys Toy

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Posted 14 April 2007 - 10:53 AM

Excellent write up. I had been working on rewiring my headlights and few other things for a few days (when time allowed), trying to figure out what needed to be changed for a ground trigger. I got the idea from Danielsterns
about halfway down the page there is a nice diagram.
http://www.danielste...ays/relays.html

Mike

#5 Uberoo

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Posted 14 April 2007 - 12:10 PM

Sticky This!!!

#6 daeron

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Posted 14 April 2007 - 05:14 PM

ANY suggestions for editing, clarity of phrasing, points I missed... GREATLY ENCOURAGED!!! I hardly even read it back through to myself when I wrote it, I figured I would sleep on it before I did that. Also, the few statements in red, I would like to eliminate... so please, critique away!

I figured I would write this as a start, and let the community as a whole help me perfect it for inclusion in the repair manual.

#7 thealleyboy

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Posted 15 April 2007 - 01:55 PM

Nice job Dae!!

The only suggestion I would make (and I don't know the answer myself) is in selecting the right relay for the application. There are different values for these, and I never knew whether I was using the correct one - or overkilling by using one too big.

Otherwise, excellent write-up that just about anyone on this Board will be able to understand.

John

#8 daeron

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Posted 15 April 2007 - 05:42 PM

Nice job Dae!!

The only suggestion I would make (and I don't know the answer myself) is in selecting the right relay for the application. There are different values for these, and I never knew whether I was using the correct one - or overkilling by using one too big.

Otherwise, excellent write-up that just about anyone on this Board will be able to understand.

John

Good point; Alot of these relays are rated in amps right on the top of them, but I failed to mention that!!! they also frequently have little wiring diagrams.. and there are many other relays (beyond just the four- and five- prong ones I mentioned) that will fit into these plugs, if you use the right wires in the right holes...

Edit made!

#9 daeron

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Posted 17 April 2007 - 08:20 PM

..so, was this good enough to make the transfer into the USRM?? (that was kinda why I wrote it..)

any tweaks/corrections to make before it goes there?

Mods?

#10 daeron

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Posted 16 January 2008 - 01:47 AM

Ach, I cannot edit my original post?!! its only been.. almost a year, eek.

I was fundamentally WRONG regarding the foglight setup!! Terminal 87A is NOT an "auxiliary output" and I can only imagine that I presumed that based simply on the alphanumeric designation. :banghead:

Terminal 87A gets powered when the relay is turned OFF.

I edited the picture I drew so that it would accurately reflect reality.. and Fuji have mercy on my soul, I hope nobody had any disasters due to my clumsy assumption... :rolleyes:

If a mod could kindly stick that big blue comment there, somewhere in my section about the foglights, I would greatly appreciate it :)

#11 Cougar

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Posted 16 January 2008 - 04:31 AM

Daeron,

I do have one small suggestion about your drawing. Instead of showing two seperate wires going between the lights and the relay I would show one wire coming from the relay (87) and then splitting to the lights.

#12 cobcob

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Posted 16 January 2008 - 08:59 AM

I was fundamentally WRONG regarding the foglight setup!! Terminal 87A is NOT an "auxiliary output" and I can only imagine that I presumed that based simply on the alphanumeric designation. :banghead:

I think on the packaging for most relays it says that 87 or 87A can provide power to the lights but it doesn't specify the switched state... No biggie though

#13 Dee2

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Posted 30 October 2013 - 07:47 PM

it would be nice to have the missing wiring diagrams.......



#14 Loyale 2.7 Turbo

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Posted 31 October 2013 - 02:01 PM

~► http://www.ultimates...d-bosch-relays/



#15 Loyale 2.7 Turbo

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Posted 31 October 2013 - 02:03 PM

If the photos of my Writeup aren't displaying now, we have to wait, 'till Photobucket resets their bandwidth counter back to zero, or use the Trick I posted Here:

 

~► http://www.ultimates...ing-woes/page-2

 

 

Kind Regards.



#16 SmashedGlass

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Posted 31 October 2013 - 04:49 PM

Thanks for posting the work-around, Jezsek. I've been right-click, open-in-new-tab each pic individually all this time :D



#17 Loyale 2.7 Turbo

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Posted 31 October 2013 - 07:11 PM

You're Welcome!

 

I'll try to do my Best to send a Payment to Photobucket, but for Now I'm sourcing certain parts from USA to fix my Wife's car...

 

Kind Regards.



#18 Dee2

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Posted 31 October 2013 - 09:43 PM

hmmmm... neither of those tricks worked for me.  Still can't see images.  Maybe someone who can see them can upload them here again ?



#19 Loyale 2.7 Turbo

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Posted 01 November 2013 - 09:10 AM

I wonder why the Trick didn't worked for you... Did you tried other proxy?

 

The other option is to Wait few days, 'till Photobucket resets their monthly Bandwidth counter, back to zero.

 

Kind Regards.



#20 Loyale 2.7 Turbo

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Posted 02 November 2013 - 10:51 PM

By the Way, seems like Photobucket just resetted their monthly Bandwidth counter back to Zero tonight, I see the images once again ;)

 

Kind Regards.



#21 Dee2

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Posted 03 November 2013 - 01:05 AM

I see the images for the article on "roundies" but I didn't find any wiring diagram images.  Is there another link ?



#22 Loyale 2.7 Turbo

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Posted 03 November 2013 - 12:43 PM

Yes, I have a couple of Pictorial Diagrams;

 

you can find one of those in my other writeup, named:

 

~► "How to Wire Dual Electric Fans on a Subaru EA82"

 

This is the Picture:

 

 

EsquemadeConexion.jpg

 

 

Also I posted another Pictorial Diagram, in my Wife's car Thread:

 

~► "The KiaStein

 

This is the Picture:

 

 

Halogens4-RelaySwitch.jpg

 

I Hope you'll find those Useful.

 

Kind Regards.



#23 Loyale 2.7 Turbo

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Posted 03 November 2013 - 12:52 PM

Basically talkin', you only need three (3) wires in order to get a Relay properly working, to Power a Device (Such like Horn, Halogens, etc...)

 

1 the Positive input shall be placed in two Spades, the Nº 30 (which is the High Power positive imput, directly from battery - To be Transferred to the Device once the Relay is On) and to the Spade Nº 86 (Positive switchin' signal) and those could have power permanently.

 

2 The Switching (On / Off) Signal, comes from the Ground, sent by a Grounded Switch on the Dashboard (or wherever you might want to put the Ground source, such like a High / Low Beams' stick, Horn button, etc...) It goes to Spade Nº 85

 

3 The Positive Power Output to Power the Device, (Halogens, Horn, etc...) goes from Spade Nº 87


Edited by Loyale 2.7 Turbo, 03 November 2013 - 01:04 PM.


#24 Loyale 2.7 Turbo

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Posted 03 November 2013 - 01:06 PM

Of course you could use a Positive signal (+) to switch the Relay on /off instead the Ground, but in such case, the Relay's ground shall be Permanently connected, and the Direct Positive imput shall goes to Spade Nº 30 ONLY, then you use a Low power positive on Spade Nº 86 to send the Switching Signal.

 

But that's a Four wiring install.

 

Kind Regards.



#25 Dee2

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Posted 04 November 2013 - 12:27 AM

thanks, I'll try to translate this to my starter.






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