 5 terminal Relay, Basic question |
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| Rleog |
 Jun 11 2014, 07:07 AM
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#1
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Senior Member  Group: Members Posts: 608 Joined: 12-October 03 From: Middleton, MA Member No.: 1,239 Region Association: North East States 
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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 |
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Replies(1 - 13)
| GeorgeRud |
Jun 11 2014, 07:14 AM
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#2
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Advanced Member Group: Members Posts: 3,725 Joined: 27-July 05 From: Chicagoland Member No.: 4,482 Region Association: Upper MidWest |
It's either/or. Seem to remember 87 is energized relay, 87a is the non energized position.
The basic relay is wired like this:  |
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| Spoke |
Jun 11 2014, 07:58 AM
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#3
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Jerry Group: Members Posts: 6,992 Joined: 29-October 04 From: Allentown, PA Member No.: 3,031 Region Association: None
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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 |
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| McMark |
Jun 11 2014, 08:07 AM
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#4
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914 Freak! Group: Retired Admin Posts: 20,179 Joined: 13-March 03 From: Grand Rapids, MI Member No.: 419 Region Association: None |
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.
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| dangrouche |
Jun 11 2014, 08:19 AM
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#5
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dangrouche Group: Members Posts: 550 Joined: 1-May 04 From: San Francisco Bay Area Member No.: 2,012 Region Association: None |
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| Cap'n Krusty |
Jun 11 2014, 08:31 AM
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#6
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Cap'n Krusty Group: Members Posts: 10,794 Joined: 24-June 04 From: Santa Maria, CA Member No.: 2,246 Region Association: Central California |
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 |
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| Dtjaden |
Jun 11 2014, 08:34 AM
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#7
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Member Group: Members Posts: 232 Joined: 25-May 13 From: Morgan Hill, CA Member No.: 15,915 Region Association: Northern California |
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. |
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| Rleog |
Jun 11 2014, 08:43 AM
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#8
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Senior Member Group: Members Posts: 608 Joined: 12-October 03 From: Middleton, MA Member No.: 1,239 Region Association: North East States
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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. |
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| r_towle |
Jun 11 2014, 09:09 AM
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#9
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Custom Member Group: Members Posts: 24,594 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States
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I used two relays on the 911.... One for each headlight.
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| Cap'n Krusty |
Jun 11 2014, 09:32 AM
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#10
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Cap'n Krusty Group: Members Posts: 10,794 Joined: 24-June 04 From: Santa Maria, CA Member No.: 2,246 Region Association: Central California |
QUOTE(Rleog @ Jun 11 2014, 07:43 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. 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 |
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| Rleog |
Jun 11 2014, 11:10 AM
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#11
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Senior Member Group: Members Posts: 608 Joined: 12-October 03 From: Middleton, MA Member No.: 1,239 Region Association: North East States
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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.
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| Cap'n Krusty |
Jun 11 2014, 11:16 AM
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#12
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Cap'n Krusty Group: Members Posts: 10,794 Joined: 24-June 04 From: Santa Maria, CA Member No.: 2,246 Region Association: Central California |
Just be sure the relays you select have sufficient amperage capacity to handle the load.
The Cap'n |
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| Rleog |
Jun 11 2014, 11:17 AM
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#13
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Senior Member Group: Members Posts: 608 Joined: 12-October 03 From: Middleton, MA Member No.: 1,239 Region Association: North East States
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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.
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| Rleog |
Jun 11 2014, 11:20 AM
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#14
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Senior Member Group: Members Posts: 608 Joined: 12-October 03 From: Middleton, MA Member No.: 1,239 Region Association: North East States
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QUOTE(Cap'n Krusty @ Jun 11 2014, 01:16 PM) Just be sure the relays you select have sufficient amperage capacity to handle the load. The Cap'n 40/60 amp |
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