Coolant fan wiring
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Northstar Engines and System Technical Discussion Discussion, Coolant fan wiring in Cadillac Engine Technical Discussion; In my review of a recently purchased '96 Eldo, I find an absolute butcher-job of a cobbled together wiring mess ...
  1. #1
    Harry Yarnell is offline Cadillac Owners Fanatic
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    Coolant fan wiring

    In my review of a recently purchased '96 Eldo, I find an absolute butcher-job of a cobbled together wiring mess of the three fan relays. It was deemed prudent to just replace (splice) the relays and wiring from a '96 Seville parts harness laying around; all the colors matched up. There are two yellow wires coming out of the harness, each one tied to pin 87a of relay #1 and #3. BUT, when consulting the '96 shop manual (pg.6E-37), these pins are blank.
    Looking at the '98 shop manual (pg.6-224) these two relay pins (87a) are connected together (wit a YELLOW lead), but don't go into the harness.
    Reading the schematic of the fans, tying pins 87a (relays 1 and 3) together makes no sense; it doesn't DO anything.
    Bottom line is, I wired (soldered) the relays into the harness, but what are those yellow leads for?

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  3. #2
    Submariner409's Avatar
    Submariner409 is offline If it won't run, slap in a big stereo
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    Re: Coolant fan wiring

    Maybe here................Looks like the yellow is part of the series/parallel fan speed control system.

  4. #3
    Harry Yarnell is offline Cadillac Owners Fanatic
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    Re: Coolant fan wiring

    look at how the fans work. Both fans are put in series for low speed operation. Then all three relays are energized, and the two fans are in parallel for high speed. The yellow lead does nothing.

  5. #4
    Submariner409's Avatar
    Submariner409 is offline If it won't run, slap in a big stereo
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    Re: Coolant fan wiring

    It is odd that the yellow seems to be nothing more than a completion of a circuit which goes nowhere.

    In the 2000+ diagram those two relay pins are blank - the "yellow wire" is gone. BUT, the relays are IN the 2000+ underhood fuse box, not external, so the equivalent PCB trace is not there..............

  6. #5
    Harry Yarnell is offline Cadillac Owners Fanatic
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    Re: Coolant fan wiring

    The yellow wire doesn't exist in the '96 manual, but it's there in the car. Thought maybe it's a late '96, but it's not in the '97 manual, but IS in the '98 manual. Go figure.

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