Changed a bad relay tonight with a spare I had in the parts box and was wondering if all relays are created equal. What came out was the silver one I replaced it with a black one.

The round metal one I'm not sure, but the round plastic ones are all the same.

I have seen them in black, red and gray.
Andy

My understanding is that the red relays were different than the black relays, and were designated to be used as fuel pump relays.

Is this true, or just another story I've heard???

Eric Read

Edit: I understand that the red relays have a noise suppression diode across the coil. Can anybody confirm this?????

Yes I believe that is the case.
(It shouldn't be hard to confirm with a simple continuity test.)

The diode helps prevent the fields created on the wires by things like a high load
motor device from being induced by the coil back into the wires that feed the relay coil.

But beyond the noise suppression,
diodes are often used to prevent a relay coil from inducing a high voltage current
from the spark/arc that occurs when a relay switches off a high current load.
The diode will create a short to drain off the current so that it doesn't back feed
into the circuitry that is used to drive the relay coil which in this case the ECU.

The diode inside the relay is bridged across the coil. Because of this, the coil
can only be hooked up one way. i.e. one side must be + and other must be -.
Without a diode, the polarity of voltage on the coil doesn't matter.

A black relay could always be used in place of a red one but you would lose
the noise reduction and back current/voltage protection.

But in order for a red relay (with diode) to replace a black relay, pins 85 & 86 would
have to have the same polarity. If not, the red relay would cause a short when
the coil was energized.


--- bill

I have also heard that some relays can handle more current than others. Supposedly the colored ones can handle more than the black ones.

--DD

The red relay is a 30 amp relay.

The black one and the metal can one are the same. 20a.


Grey relays... I always thought they were painted, not grey.