I'm adding relays to my headlight circuits.
The 5 terminals and their functions:

30 = current input
86 = trigger current input
85 = ground
87 = current output
87b = current output ?

My question: when the relay is triggered, are both 87 and 87b active, or is this an either/or arrangement?

I'm hoping to wire one headlight to 87 and the other to 87b.

Thanks

It's either/or. Seem to remember 87 is energized relay, 87a is the non energized position.

The basic relay is wired like this:
Click to view attachment

The 87b relay contact appears to be in parallel to the 87 relay contact. See images in the link below.

So you should be able to connect both headlights to the same relay provided each contact can handle the current of one headlight.

Relay with 87b

Use an ohm meter to check between 30-87 and 30-87b. Whatever the state of those, they will likely reverse when the relay is triggered.

http://www.youtube.com/watch?v=F1SGyN6Yp64

here's a 20 minute tutorial on youtube

There are also 5 pin relays with 2 terminal 87s, which are energized together. Handy when you need to power up 2 separate circuits.

The Cap'n

Current will flow from pin 30 to pin 87a when the relay is inactive (when there is no current flowing between pins 85 & 86). Current will flow from pin 30 to pin 87 when the relay is active.

So the answer to wether you can connect one headlight to pin 87 and one to pin 87a is no. These relays are rated at 30 amps so there should be no problem hooking both headlights to one relay, both to pin 87. 30 amps at 12v = 360 watts, far more than the two headlights would draw.

I have the 5 terminal relay with 87 and 87b, so it looks like Spoke has the circuit diagram that applies.

Evidently the 87 and 87a type relay is the either/or one also described above.

Fortunately, I ordered the correct ones.

Thanks.

I used two relays on the 911.... One for each headlight.

Am I missing something? (Won't be the first time!) Why not use a 40A 4 pin relay? Cheap, bulletproof, and readily available.

The Cap'n

Not likely you're missing anything. That's usually my game. I guess the answer is that I didn't know the easiest/best way.

Just be sure the relays you select have sufficient amperage capacity to handle the load.

The Cap'n

Rich: as I have it now, I have 3 relays up front, Hi, Low, and Fog, with left or right beam powered off the 87 or 87b output, respectively. 12 Ga wire direct from the battery to a fuse block up front connects to the relays.

40/60 amp