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  1. #1

    Default explaination for numbers on a 12v relay

    I am curious if anyone knows where the numbers they use on most relays came from(30, 87, 87a)? I know what they do, just curious why they are the way they are.

    98 Silverado
    5.7 vortec
    14 bolt posi rear, with 373s
    33" wild countrys
    tube steps, chrome kit, fenderflares,
    chrome diff plate, window flares,
    2-10"Alpine TypeE, Alpine 450watt V-Power.

  2. #2


    They have to do with standardization assignments. Read down a little in this thread and someone gives an explanation.
    Last edited by troutbug; 02-05-2011 at 02:03 AM.

    2008 Silverado 1500 LT 5.3L Crew Cab
    Desert Brown Metallic

    Century top, Yakima roof rack, 2.5" front lift, Readylift 3" rear blocks, Line-x bedliner, step bars, AVS vent visors, Weathertech floor liners, door sill guards, power tailgate lock, tailgate damper, KC light bar w/ PIAA 525s, rear mini-light bar, rear LED reverse/utility lights, dual batteries (Cole Hersee isolator), DIC upgrade, 20" GM wheels, Cooper Discoverer A/T3s, 26 gal. onboard air (twin Viair 480Cs), Nathan Airchime K3HA / Old cast 2nd Gen. P3 Horns, Graham White valve, bell

    Past Chevys: 1985 S-10, 1963 BelAir sedan

  3. #3
    stephan's Avatar
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    Sep 2010
    Far West, Oregon USA,
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    That's a great link Sal, thank you for posting it. I copied & pasted it into an email that I'm sending to everybody that calls and asks what's this # or that # mean. My list got so dirty it was unreadable & I finally threw it away, & my memory was only good for less than 20% of the total on the list lol
    1988 Chevy C-3500 2wd (no pic)
    350 c.i. 5.7 L Stock Block, 4 Bolt Mains
    L-31 Vortec Heads, Edelbrock Cam & Intake,
    Holley 650, Flowtech Headers, Magnaflow exh.
    Jet Trans 700R4, B&M Ratchet, 4:10 gears,
    3" susp. lift kit "shadetree"
    No rev limiter, No speed limiter lol

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