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Electric choke wiring

Discussion in 'Electrical & Audio' started by Norwester, Dec 23, 2016.

  1. Norwester

    Norwester Full Access Member

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    Joined:
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    Location:
    Battle Ground, WA
    First Name:
    David
    Truck Year:
    1986
    Truck Model:
    C-10
    Engine Size:
    350
    On my '86, the PO installed a 350. While he did what looks to be a reasonable job, I'm still finding issues and am trying to clean them up.

    I've been trying to adjust the choke on my Edelbrock 1406 with no success. Today I put a meter on it and found no voltage going to the choke.

    I traced the wire and it eventually ends up somewhere in the dash. Choke light maybe? Regarding the light....it comes on when I'm cranking and then immediately goes out upon starting, regardless of outside temperature.

    I found another thread about the choke wiring and it says the wire should be attached to the oil pressure switch. I have a mechanical oil pressure gauge and I found where it attaches to the engine and right beside it, there was what I believe to be the switch.

    The problem is that it is so buried back there behind the distributor, I have no idea how I'd get in there to splice it in.

    Being inherently lazy, I'm looking at what might be a better choice for switched 12V.

    I've read where people have spliced into the wiper wiring. I put the meter on the wiper wiring and found all three wires registering 11.8V. This was the harness going into the motor. The colors were white, gray, and purple. None registered hot with the key off.

    Would this be a good way to go? If so, does it matter which color wire I use?

    If it's imperative to use the oil pressure switch, any hints as to how to get back in there? I'm an old fart and my body doesn't twist and turn as it might have 40 years ago.

    I do appreciate any ideas you folks may have.....and MERRY CHRISTMAS!
     
  2. Quadrajet Power

    Quadrajet Power Full Access Member

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    First Name:
    Mark
    Truck Year:
    1989
    Truck Model:
    K5 Blazer
    Engine Size:
    350
    Any key on power source would work. Don't use ignition wiring though. Best would be to use the fuse block if you can.
     
  3. Norwester

    Norwester Full Access Member

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    First Name:
    David
    Truck Year:
    1986
    Truck Model:
    C-10
    Engine Size:
    350
    I very much appreciate the advice. Thank you
     
  4. chengny

    chengny Full Access Member

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    Location:
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    First Name:
    Jerry
    Truck Year:
    1986
    Truck Model:
    K3500
    Engine Size:
    350/5.7
    If your choke light goes out as soon as the engine fires (and 10 psi of oil pressure is established), it is probably safe to assume a couple of things:

    1. That the oil pressure switch is working (i.e. contacts are closing as designed) and

    2. It is wired correctly - at least to the dash/choke lamp

    The choke warning lamp receives power (as do all the other gauges and warning lamps like oil pressure, coolant temp, brake warning, fuel tank, voltage, etc.) from the 20 amp fuse in the slot labeled Gauge/Idle. It is supplied via a common PNK/BLK lead.

    The choke warning light has one major difference, its other leg is not wired directly to ground - as is normal with most lamps. The other leg can be either a ground or an opposing power supply - depending on whether the oil pressure switch is back feeding to the lamp, or supplying power to the choke heater coil.

    Power to the oil pressure switch is from the 20 amp CHOKE fuse on a pink/white lead.

    The other side of the pressure switch has two leads coming out. One (a light blue) runs around the back of the distributor and is plugged into the heater coil. The other (a dark blue) heads back through the firewall and is connected to one side of the choke lamp.

    The harness plug is misleading. It appears that it should connect to a 3 prong switch, but the DK BLU and LT BLU are spliced within the casing:

    [​IMG] [​IMG]

    The power supply to the choke heater coil is simply spliced onto the lead that runs back to the IP - from the switch - and controls choke light operation.

    When the switch sees oil pressure, its contacts close - and both the BLU leads become hot. Consequently, the choke heater begins to assist in opening the choke plates and in addition the warning lamp in the IP goes out.

    This is due to the fact that - with 12 VDC now being applied to both legs of the lamp - there exists no net flow of electrons through the filament.

    I don't know how interested you are, but the wiring diagrams below explain what I mean.

    [​IMG] [​IMG] [​IMG]

    I hate to see the choke light wiring changed because - when lit, with the engine running - it is actually a visual indication that oil pressure is dangerously low (below 10 psi).
     
  5. Norwester

    Norwester Full Access Member

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    Joined:
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    First Name:
    David
    Truck Year:
    1986
    Truck Model:
    C-10
    Engine Size:
    350

    As always, you're a wealth of good info. It sounds like I need to tap into that lt blue wire. I'll have a look and see if I can do that. Thanks for the reply.
     

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