Headlight relays

[KEH]

While at the salvage yard today I picked up a couple of relays off of an s/10 to use for my headlights. I remembered that on the FAQ thread Longhorn Man said to grab the ones on the drivers side.

However, I forgot he said to get the ones from the firewall and ended up with the relays from the drivers side fender.

They don't have the terminal numbers stamped, only colored wires.

Are these usable or do I need to get different ones?

[neonlarry]

I don't know much about S/10's but you can compare the relays you got to these.
http://order.waytekwire.com/CGI-BIN/...31D041+M37+ENG
click on the 'Click here to view catalog page' it is a PDF file (need Adobe Reader). Also has the pinouts for the various relays.

[neonlarry]

I can't get that link to work. Go to http://www.waytekwire.com/
Then Products, Then in select category Relays, Then High Capacity Then ^ View .....

[Longhorn Man]

can you get pics of your relays?

[KEH]

Thanks for the reply. Here are the pics:

[Longhorn Man]

hmmmm, I can't help you on those man. Sorry

[KEH]

Bummer! Are the firewall relays easy to figure out the connections for?

[neonlarry]

You can buy them new from the link I gave and they are fairly cheap.

[mocwon]

It's my understanding from one of our electrical engineers at work that relays are not necessary for a 2-headlight setup given the amp draw and the factory wiring size. Does anyone have facts to the contrary???

Originally Posted by KEH

Thanks for the reply. Here are the pics:

[4x4Poet]

Depends on how you define "needed," mocwon. In our original trucks, the factory wires are fine to run the headlights, but relays enable the use of short, large-gauge wires that draw power directly from the battery or alternator with less resistence than power going thru the headlight switch. The resulting higher voltage (and amps?) bring more power to the headlights and thereby make them produce more light than the factory wiring that sends the headlight power thru the headlight switch and back out to the headlights.

[70GMCer]

So, is there a FAQ on how to do this?

[Longhorn Man]

yup http://67-72chevytrucks.com/vboard/s...d.php3?t=92228 first page of FAQ.

As for needing verses not needing the relays... you'd be lucky to get 12 volts to the headlights the way they wired them up originally. On mine, the wires had aged, and the poor design in general had created enough resistance to get a whopping 11.75 volts to the lamps.
Ever notice old cars and trucks have orangish lights...even when you install new lights? This is the reason. (And for the record, haligon lights, or the new fangled conversions to use blue bulbs and what not, put even more stress on the old wires due to a higher current draw.)
Now that I have mine rewired with the relays, my lights are getting a full 13.8 volts, which is exactly what is avalible at the batterys. (engine running at high idle) There is no voltage drop at all, and the lights can get every amp they want. There is a noticeable increase in light out put, and the wires going to the headlight switch and the highbeam switch won't get hot, not to mention the fact that those two awitches are doing less work now ad should last forever...not that they wear out oo often from use.

[KEH]

noenlarry,

Thanks for the link. I was interested in s/10 relays because of the tight connectors that I grabed with them.

[mr402]

Check these guys our for inexpensive relays. Buy 10 or more and they're only $2.00 each.

http://www.allelectronics.com/cgi-bi...351&type=store

They also have the wiring harnesses for them at $1.50 each. The wiring harness allows you to gang a few together as well.

http://www.allelectronics.com/cgi-bi...Y-2&type=store

I've purchased from them a few times and have been impressed by their responsiveness. While your there they have great prices on the plastic split wire loom tubing.

http://www.allelectronics.com/cgi-bi...583&type=store

Shipping is a flat $6.00 no matter how much you order.

Need less to say I stocked up on relays and tubing plus a few other things.

No, I don't work there or know anyone there. Just have had very good experiences so far.

[Russell]

The relays in question will do very well for the headlights

There are a couple different types of relays that this relay will be:

It'll a normally open or a normally closed relay. Sometimes both. Normally open means that without the relay's solenoid having power delivered to it, the circuit is open, or not connected. Normally closed is the opposite way, applying power to the relay's solenoid opens the circuit. To find out what type relay it is, use a volt meter and look for continuity between the two poles. Keep in mind that the two solenoid poles will always have continuity between them.

The other thing you'll need to look at is how the relay is connected. There are two types I've seen, a 3 wire relay, or a 4 + wire relay. A 3 wire relay will have a common positive, or a common ground, with the switch providing the opposite pole. This means that if you have an ECM that sends a negative signal down to the relay to provide a positive power lead to another system, the other system will have a ground already, with the positive solenoid, and the hot wire being connected together, the other part of the hot wire that is switched on and off by the relay onto the other pole, and the final wire being the ground wire that either turns the solenoid on or off. A 4 wire relay will have a positive and a negative wire for the solenoid, and two other wires that go in between whatever is being switched and the power source. If it has more than 4 wires, usually 6, then two will be for the solenoid, 1 will be for normally open, one will be for normally closed, and the other will be the switched wire.

Yeah, I know, this is about as clear as mud, I'll post up a couple diagrams later on once I get home and they'll clear everything up :P

However, as far as the headlight relays go, simply find out what type of relay it is, then hook her up! All relays are essentially the same thing, simply an electronic switch that allows for a low amp wire to control a high amp wire. All relays can be used for any purpose, just need to know how they hook up first.

[KEH]

Cool. I look forward to learning more. Like how to determine which unmarked pole is for what. Thanks.