toggle switch S relay

[areonic1]

So I been sitting here debating on the relay box for ms. Although I do have the car already hooked up and idling, but just thought maybe for preventing of electrical issues. Now, what is the point of a relay? Such as, lets say I run a wire from 12v source, to a toggle switch, then to the MS, why is a relay needed?

I know a relay is somewhat similar to a switch I beieve, as in it turns power on or off to the item. But a toggle switch does the same, just a relay requires more wiring then a switch. So my main question is what is the point of a relay?

[phj420]

well, you would use relays so that you could have the computer control things, safety, and to prolong the life of your switches.

You would want the fuel pump to be on a relay so that it can be controlled by the computer/ignition switch through main relay. It is a safety issue, and most of the time you don't want fuel pressure when the engine is not running. It is also recommended that you have an inertial safety switch installed on the fuel pump so that if you get into an accident your fuel pump shuts off. Otherwise, in the event of an accident, or other problem you could potentially have a big fire.

The use of a main relay is advantageous to prolong the life of your ignition switch. You can run a small amount of current through your switch and thus keep it working. Most Ignition switches are not rated for high current. I went through a few ign switches in the early days. It is also nice because if your relay fails it is easy to replace, unlike the switch.

I am using the relay board and I like it. It really simplifies the wiring, and it has polyfuses on it so that if you try to draw too much current it acts as a breaker. I know that fidle is one that can only handle a small amount of current and people frequently use too much current and blow something when they wire it directly. The relay box is also nice for troubleshooting. Everything is labeled at a central place and easily disconnected/jumpered. It is also nice because it has all of the fuse holders built into the board. Much easier.

[areonic1]

Thank you so much, I have been looking for that answer forever,lol

[vinister]

relays are great but I wouldn't waste your time with the relay board. As long as you have a proper crimper, just wire them up yourself.

[phj420]

Don't crimp, solder. There is less potential for noise and failure when you solder your connections.

[areonic1]

Are you saying, use relays, but just dont waste the time/money using a board?

[vinister]

Ya exactly. If you understand how a relay works and know how to properly wire it (soldering is good, but then you can never un-plug it in case of a failure). I use female crimps, I use dozens per day as part of my work, and I haven't had one fail in years. I agree on the soldering, all signal wires and grounds should always be soldered, but something like a connection to a relay, you have to keep in mind that the relay will fail one day and you'll have to unplug it. It can also be helpful for troubleshooting if you have the option of unplugging leads for testing.

The relay board just connects the db37 pins to the right pins on the relay. If you know how to do that, then there isn't much use in a relay board. I find the install cleaner without it, and troubleshooting is simpler, as many of the leads can connect directly from the db37 to their respective sensors/injectors/etc. If you don't use the relay board then you eliminate 2 connection points (failure points) along the way.

[phj420]

I am not saying that you should solder directly to the relay, I am saying that you should solder to a connector, grease it with dielectric grease, then attach it to the relay. I think that it looks cleaner when you use the relay board, but others might disagree. I think that it really depends on the application. If you are going for a clean install and you will see the wiring the relay board is a must. I have a sand rail with no real fuse location or body to hide my wiring, so in my case the relay board was the best choice. If I had a nice waterproof, hidden place to put the relays in line I would have saved the money and not used the relay board .

I did have to build an enclosure around the board due to the fact that I have no engine compartment. The limited amount of space that I had to work with meant that the relay board solved a lot of wiring challenges for me. I also like it because it allowed me to mount my MS in a remote location.







Ultimately it depends on your application and budget.

[areonic1]

Thanks guys, been tons of help.

The thing is, I have fuse blocks, relays and 12 pin terminal rails laying around and have given thought to just making my own, with stuff I already own, instead of wasting 60-90 bux on one. Just didnt know if it served any other purpose, and just wanted to make sure the relays were "must".

Anyways, Thank ya lots

[vinister]

absolutely do it yourself then. I have the exact setup. My DB37 breaks out to 2 long terminal strips, mounted about a foot away from the ms box. From there I have a small fusebox-type-thing, a couple of relays, the LC-1 stuff, etc. I soldered the ring terminals for both sides of each rail on the terminal strips. I have this all mounted to a large ABS plate that hinges off the firewall under the passenger side dash, held up with thumbscrews. Access is easy, undo the thumbscrews, lower the panel, and I have access to every pin on the db37.

edit, picture's worth a couple dozen words (don't mind the breadboard its not a permanent part of the install obviously)



In the top left is a strip for ignition and grounds, to the right of that is the 8-position fusebox deal.

Top right silver box is the car-pc power supply. 2 relays on the left edge and 2 terminal strips for the db-37 and associated wiring

[Mike_Robert]

Please remember that a poor joint is a poor joint whether it's crimped or soldered. Soldering always creates an area where your multi-stranded conductor is effectively turned into a solid wire and is susceptible to cracking. That said, a good solder joint is easier and cheaper to make than a good crimp joint. I personally use aviation style cabling techniques (crimping, taking care to use the correct connector, good prep and use of an $85 ratcheting compound crimper) with just a touch of solder to be absolutely certain conductivity is flawless. Adhesive lined heat shrink assists with strain relief/fatigue protection. Dielectric grease, as suggested by phj is a great idea!