Relay Wiring question.

[Muad'Dib]

I have both SPST and SPDT relays that im wiring up. Im using the SPDT Relays as SPST's (basically just not using 87a).

From what i understand, 85 and 86 on the relay can be wired anyway you want too. So the switched +12v can go to either 85 or 86 as long as the other is used for ground.

Is the same principle true for 30 and 87? When the coil is energized and the internal switch closes completing the connection between 30 and 87 i wouldnt think it would matter which way the voltage and current is flowing... Am i wrong here?

Advice is appreciated. Thanks!

[TNT]

I have both SPST and SPDT relays that im wiring up. Im using the SPDT Relays as SPST's (basically just not using 87a).

From what i understand, 85 and 86 on the relay can be wired anyway you want too. So the switched +12v can go to either 85 or 86 as long as the other is used for ground.

Is the same principle true for 30 and 87? When the coil is energized and the internal switch closes completing the connection between 30 and 87 i wouldnt think it would matter which way the voltage and current is flowing... Am i wrong here?

Advice is appreciated. Thanks!

Here is the proper wiring info on ISO relays.



#85 and #86 are for the coil so it can be wired two ways.
1.) I could have a constant power source on one and a switched ground. This is how most new cars do it to eliminate voltage spikes.
2.) It could also have a constant ground on one and a switched power supply on the other. This is how most overlay harnesses that eliminate the voltage drop so the headlights recieve full voltage.

I use #85 as the input and #86 as the switched side just to keep things consistant.

The #30 terminal is the input(it could be power or ground depending on your needs). This #30 terminal should always be used as the input.

#87 is the output when the relay's coil is energized.

#87A is the output when the relays coil isn't energized.

The relay can switch power or ground depending on your needs.

[Muad'Dib]

I have both SPST and SPDT relays that im wiring up. Im using the SPDT Relays as SPST's (basically just not using 87a).

From what i understand, 85 and 86 on the relay can be wired anyway you want too. So the switched +12v can go to either 85 or 86 as long as the other is used for ground.

Is the same principle true for 30 and 87? When the coil is energized and the internal switch closes completing the connection between 30 and 87 i wouldnt think it would matter which way the voltage and current is flowing... Am i wrong here?

Advice is appreciated. Thanks!

Here is the proper wiring info on ISO relays.



#85 and #86 are for the coil so it can be wired two ways.
1.) I could have a constant power source on one and a switched ground. This is how most new cars do it to eliminate voltage spikes.
2.) It could also have a constant ground on one and a switched power supply on the other. This is how most overlay harnesses that eliminate the voltage drop so the headlights recieve full voltage.

I use #85 as the input and #86 as the switched side just to keep things consistant.

The #30 terminal is the input(it could be power or ground depending on your needs). This #30 terminal should always be used as the input.

#87 is the output when the relay's coil is energized.

#87A is the output when the relays coil isn't energized.

The relay can switch power or ground depending on your needs.

You state here that pin 30 should always be used as the input, but from what i understand the circuits are completely isolated and ungrounded...

Normally i would use pin 30 as the input, it just so happens i started wiring, and realized that i was wiring for input at 87 instead of 30. I would be helpful if i know for sure if it worked in reverse so that i can save some wiring and connectors, and not have to re-do the whole project.

Seems only logical that the when the coil energizes that it just completes the circuit between 30 and 87 (continuity).. so it really "shouldnt" matter which is input and output...

Is what you stated difinitive?

[TNT]

It will work if the input is on #87 and power output is on #87. It's not correct but it shouldn't hurt the relay.

Remember that #87a will no longer function when wired that way.

I was stating the correct wiring for the relay.

[Muad'Dib]

Solved and closed..

Just in case someone runs across this in the future, i havent had a chance to actually test everything, but multiple sources say that the relay will work fine with pin 87 being the fused 12v input, and 30 being the output. This is only applicaple in SPST applications as it would cause pin 87a to no longer function on a SPDT relay.
So if your like me and wired it this way and accident, and dont want to re-do everything .. it should be fine. It isnt the "proper" way to do it, but it will work.