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5 Pin 40 Amp Relay FAQs

All Customer Questions

5 Pin 40 Amp Relay
5 Pin 40 Amp Relay
Q: Is it necessary to fuse a 12 volt wire going to a toggle switch to a 30amp relay?
A: Yes, you should always fuse a wire coming from the battery, regardless of where it's going.
Q: I have an amplifier fan that draws less than 1 amp of current. Is a relay necessary or should I just hook it up to a switch? - by Luis
A: I see no reason to use a relay in this case. I'd simply use a switch, as long as the switch is capable of handling 1 amp of current.
Q: which pin would generally be common contact, open contact, and close contact - by kory (vancouver, wa)
A: Please accept my apologies, but I don't really understand the question.

A relay basically works like this:
When the coil (Pins 85 and 86) is energized, Pins 30 and 87 will be connected.
When the coil is not energized, Pins 30 and 87a will be connected.
Q: Do you offer 30 to 40 amp. relays with 6 volt coils
A: This relay has a 12 volt coil. Please accept my apologies, but we do not offer a 6 volt coil relay. I'd suggest an electronic parts distributor such as Mouser, Digikey, etc.
Q: If I were wiring up a pair of retrofitted HID Projector Headlights, will this 40amp relay be enough to handle both or do you recommend the use of a different relay on your site?
A: This relay should be fine for that. I'd just use a relay for each side.
Q: in the photo showing the 5 pins, is:
30 top, 85 rt. 87 bottom, 86 left, 87a center? - by bill (miami fl)
A: Yes
Q: Does this relay come with a built-in diode? Or should I install a diode along with this relay? In doing some google searching it seems to indicate that a diode is necessary to prevent a voltage spike when the relay is turned off. - by Michael (Lakewood, CO)
A: There is no built-in diode. All relay coils initiate an inductive current spike when dropping out. This current will destroy any CMOS or integrated circuit. Diodes are needed to dissipate this energy only when relays are used in solid state circuits. Also, the diode must have the correct orientation. Check the Internet for applications. Hope this helps.
Q: The CMC brand aftermarket power tilt and trim PT-130 for OB motors uses 2 40 amp 5 pin relays to reverse the unit from up to down and down to up. These relays look identical to the ones supplied. Do you think that they would be direct replacemnts? - by Don (Tallahassee FL)
A: I'd assume so. This is a pretty common relay.

If it looks like a duck, swims like a duck and quacks like a duck, then it probably is a duck =)
Q: Will these work for other relays in a car, such as turn signals or wipers?
A: It depends what type of relays are used for those things. With the proper wiring, relays can be used for many applications.
Q: I'm hooking up 3 sets of cathode kits to one switch and its not bright. They are red. Would a relay help to make it brighter? - by chris (Round Rock, TX)
A: Red is inherently a dim color, and a relay won't really affect the brightness. I'd suggest using more lighting until you achieve your desired brightness level.
Q: How would I wire this up for a negatively switched wire from my footwell lights that dim? And which pin do I use, 87 or 87a?
A: The relay has 5 pins:

85: Constant 12v (fused of course)
86: Negatively switched wire from your dome light
87: Output to positive of footwell light source (LEDs, cathodes, etc).
30: Constant 12v (fused of course)
87a: (leave disconnected)

And then you'll just ground the footwell light source (LEDs, cathodes, etc).
Q: Can I hook up several cathode kits to one relay, or is the relay strictly for one kit only?
A: You can hook up tons of things to a relay. Considering a cathode kit only draws .7 amps, and this relay can safely handle 30 amps... 30 / .7 = about 42 cathode kits on one relay.
Q: What exactly is a relay? What is its purpose? - by Michael (Kansas)
A: A relay is an electrical switch that opens and closes under the control of another electrical circuit. For instance, if you wanted to use a wire from your vehicle's ignition, which usually does not carry much current and is not able to handle large amounts of current, to turn on a large power inverter you've installed.

Here's some good basics on relays:

HowStuffWorks
Wikipedia