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Posted by: Rleog Jun 11 2014, 07:07 AM

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

Posted by: GeorgeRud Jun 11 2014, 07:14 AM

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

The basic relay is wired like this:

Posted by: Spoke Jun 11 2014, 07:58 AM

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.

https://www.google.com/search?q=87b+relay&client=firefox-a&hs=uQ5&rls=org.mozilla:en-US:official&channel=sb&source=lnms&tbm=isch&sa=X&ei=L2CYU8XFLa_MsQTckYHYBw&ved=0CAoQ_AUoAw&biw=1252&bih=638

Posted by: McMark Jun 11 2014, 08:07 AM

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.

Posted by: dangrouche Jun 11 2014, 08:19 AM

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

here's a 20 minute tutorial on youtube

Posted by: Cap'n Krusty Jun 11 2014, 08:31 AM

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

Posted by: Dtjaden Jun 11 2014, 08:34 AM

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.

Posted by: Rleog Jun 11 2014, 08:43 AM

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.

Posted by: r_towle Jun 11 2014, 09:09 AM

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

Posted by: Cap'n Krusty Jun 11 2014, 09:32 AM

QUOTE(Rleog @ Jun 11 2014, 07:43 AM)

Posted by: Rleog Jun 11 2014, 11:10 AM

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.

Posted by: Cap'n Krusty Jun 11 2014, 11:16 AM

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

The Cap'n

Posted by: Rleog Jun 11 2014, 11:17 AM

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.

Posted by: Rleog Jun 11 2014, 11:20 AM

QUOTE(Cap'n Krusty @ Jun 11 2014, 01:16 PM)