what is the differences between these relays?

both come out above the fuse box, i marked in red parts i dont know about can some clear them up for me?
and lastly can either relays be used in a emergency?
(my headlights went out on me the other day while a bit away from home had replaced white relay with another white relay when i got back.)


thankyou for reading
bubbad.

If the pins are PHYSICALLY the same, they should be the same being the same rating 12v 40A. The red thing in the bottom one is to symbolise what contacts the relay coil is operating. ie, when the coil in energised, it will close 87 and 30.

You can use either in an emergency. But if you are meant to use the top one then you should use it as the bit you marked red is a protection diode not 100% sure but thats what it should be). as for the red bit on the second on is there to show the link between the magnet and the switch.

thankyou for replying, ill consider looking into the diode.
thanks again.

im not 100% sure about it, but cant think of anything else that it could be. but b the looks of the diagram it is inside the relay, so if you are looking for a replacement you should look for one that has it as it would be easier then trying to make a work around.

Yeah that is usually a reverse connected diode to reduce the energy given off in the discharge of the coil... Picture the coil in your relay like the coil in your car...

When you put power across it, it charges and generates a magnetic field.

When you turn the power off the magnetic field collapses back into the windings and generates a massive spike in the reverse direction (potential wise that is).

This causes the spark across your spark plug, in a really it sends it back to whatever switched it on... The spike isn't as big on a really as it is your coil (coil is designed to spark, relay isn't), but as electronics when on and got more sensitive it became a mandatory requirement.

The diode is inside the relay. The other one will work fine though and probably never cause trouble... Just like anything, as time went on the design was refined...

Cheers,
Tim