Thread: wiring a relay

Tweet

at the NCOC auto class I take, our class was split into 2 groups, my group is doing a series circut, in which we built a realistic series circut, using the door from a junker '92 Buick Century ( a crash test car actully, car only had 300 miles on it but it's 1 of our parts cars ). we took the rear drivers door off and we'v got a stand built for it, and we started wiring it. we have the main fuse box from a '92 Chevy Lumina now. we were going to just use a fuse, but I heard my teacher mumbeling to himself, for the second stage of the project he was going to throw us a fast ball, and as I had the window wiring diagram out for the car, he noticed that there was no relay in the circut, and was supprised by that. so me and a couple others figured we would stay 1 step ahead of the teacher and run a relay, so were running 1 of the 5 pin relays that was in the fuse box. I wired it, but it dosn't work. I Ohm checked the relay and pin 30 has continuity to 87A all the time, I ran a wire from 87A to the correct power wire in the door, and grounded pin 30, I know this is wrong now because I found out pin 30 is high current output. I knew that 85 goes to 86 and is the low current side of the relay. but just to make shure as it has to work tomorrow, I ground 86 and add power and a switch to 85, then run constant power from 87 to 30 right? were just going to use an on/ off switch to operate the relay.

now I see how it works. me having it plugged into 87a has current going through it with relay open, so when I applied power to the relay windings ( could hear them click ) it switched from 87A to 87 and therefor 87A no longer had juice going to it. so all I gotta do is pull out the 87A connector and run the power wire to 87. thanks

What Denny posted is a Single Pole Double Throw relay. What is sold in a lot of auto parts stores are Single Pole Single Throw relays.
The relay you are dealing with should have a diagram embossed on the case.

yes it does have a diagram, but it's crap ( hard to decipher ). tho it does show 30 going to both 87a and 87, so what denny posted is correct with the relay I have

They will both show that. The difference is that 30 and 87a are internally connected on a single pole relay.

well, I did get it to work, but due to another student insisting on half doing it when we started, I had to compleatly rewire it. the student insisted that we just run the high current thru the wires coming out the door for power, and use an extra switch to activate the relay windings, which is what we originally did, and I had it working using the diagrams given here. the teacher told us to rewire it compleatly in series so the door switch activated the relay. now we tried to get it, but couldn't get it, turned out we were using the wrong wire ( the color codes are diffrent between the wiring out of the door, and to the door switch ) so we just direct wired thru a fuse, and because another student hooked up the power and neg to the 2 posts of the switch, burnt it up, cooked it, so we need another switch. it was due today, the kid that originally screwed us found it more important to work on his truck. but teacher knows is all we need is a switch.