Relay Wiring Pins 85 And 86

[pugpete1108 62 1 Cars]

just been looking at some wiring diagrams for 4 pin relays and noticed they all have switch live going into pin 86 and earth to pin 85 i have mine the other way round, would this matter or will they work correctly either way?

[ade 4wd 11]

Pins 85 and 86 are for the coil and can be connected either way round to switch the relay.

 

Ade,

[DrSarty 90 1 Cars]

No it doesn't matter.

 

Pins 85 and 86 are on the trigger/activate circuit, which is usually activated by a live on one pin and a switched earth/gnd on the other OR a gnd on one and a switched live on the other. It doesn't matter which way round.

 

Likewise, it doesn't really matter with pins 30 and 87, although they are on the accessory circuit, be they injectors, a fan, a fuel pump or whatever. This is the high current circuit, but is just a circuit with a switch/breaker in it, activated by pin 85 or 86 as explained above.

 

Simple answer = no. Explanation is just to help anyone baffled by relays, as they seem to hold some black magic on here for some which I'd like to remove if possible.

 

Best visualised here:

 

EDIT: The coil Ade is referring to is the little box in the centre with a diagonal line. This energises and completes the accessory circuit between pins 30 and 87.

Edited September 30, 2009 by DrSarty

[pugpete1108 62 1 Cars]

cheers boys, i understand how they work but was unsure if the polarity was specific for each circuit.

 

i need to spend some time going back over the wiring as something isnt right

[DrSarty 90 1 Cars]

Yes it's specific for a certain circuit.

 

Pins 30 & 87 will always be a power circuit, understandibly.

 

Pins 85 & 86 will be energised as I said either by an earth or a 12v feed. So whilst the orientation of the pins doesn't matter, what type of switching/energising method used is.

 

Does that make sense?

Edited September 30, 2009 by DrSarty

[pugpete1108 62 1 Cars]

perfect cheers

[leon 1.9 0]

No it doesn't matter.

 

Pins 85 and 86 are on the trigger/activate circuit, which is usually activated by a live on one pin and a switched earth/gnd on the other OR a gnd on one and a switched live on the other. It doesn't matter which way round.

 

Likewise, it doesn't really matter with pins 30 and 87, although they are on the accessory circuit, be they injectors, a fan, a fuel pump or whatever. This is the high current circuit, but is just a circuit with a switch/breaker in it, activated by pin 85 or 86 as explained above.

 

Simple answer = no. Explanation is just to help anyone baffled by relays, as they seem to hold some black magic on here for some which I'd like to remove if possible.

 

Best visualised here:

 

EDIT: The coil Ade is referring to is the little box in the centre with a diagonal line. This energises and completes the accessory circuit between pins 30 and 87.

 

Maybe not in this case (well actually, definitely not in this case), but for bonus points, what else should you sometimes do when fitting relays into electronic circuits?

[ade 4wd 11]

Put a diode across the coil to stop back EMF.

[DrSarty 90 1 Cars]

Put a diode across the coil to stop back EMF.

 

That's why I listed in my recent relay box designs the use of a VWP diode relay for the ECU power circuit.

 

As you've said, in the kind of circuit we're talking about here (injectors and FP relay most likely), the orientation of the pins doesn't matter. Whether the relay is ground switched or 12v live switched does matter.