Electric choke simple wiring

Discussion in 'Tech Discussion' started by 73c20jim, Oct 30, 2018.

  1. 73c20jim

    73c20jim Supporting Member Supporting Member

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    Read several threads about this but need some simplification.

    Car currently has manual oil pressure gauge.
    Currently has manual choke Eddy 1405.

    Installing Qjet with electric choke.
    Installing new gauge cluster with electric oil pressure gauge.
    New cluster has provision for choke light.

    Have new sender for oil pressure gauge to be installed near dizzy.

    ---------------

    I need a SIMPLE wiring diagram to have choke, choke light and electric oil pressure gauge all operational.

    ANY help is greatly appreciated. All of this will be new wiring as currently I have none of these.

    Thanks.
     
  2. Matt69olds

    Matt69olds Member

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    The top diagram uses the alternator field wiring to power the relay. With the engine running and the charging system charging, there is power on both sides of the charge light, keeping the light off and the choke relay on. if the engine dies, or the engine isn’t running, the regulator in the alternator will provide a ground for the relay, turning on the light, and turning off the choke relay. If you have a charging system light, this is the method I would use. I’m not sure if it would work without a charge light, I have never tried it. the bottom diagram uses a oil pressure satay switch from a Vega. Either way would work well. 1DBDA2D0-36EC-4402-BEBB-D94C2257B3BF.jpeg CA190153-25D0-4F49-97CE-F690EE807206.jpeg
     
  3. chengny

    chengny Full Access Member

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    If I am reading this right - before you even get into the wiring - you might need some more parts.

    First, operation of the choke heater and CHOKE warning lamp will require the installation of an oil pressure switch:

    1.jpg 2.jpg

    The sender needs to be dedicated to the gauge. It is used to position the needle - of the pressure gauge - in response to changes in oil pressure. It does this by providing a variable resistance (which controls current flow) to ground in the gauge's sensing leg.

    On the other hand, the switch has a set of NO contacts that close at around 10 psi. When they close power is supplied to the heater coil and also shuts off the CHOKE light.

    How and where to mount the two components is another problem. There is limited space under the distributor for mounting both. The factory solution was to use this fitting:

    P1010007.JPG

    Problem is finding these special fittings - as new they are NLA everywhere. The good news is that the junkyards are full of trucks that came with them.

    Another option for mounting either the switch or sender is in the tapped port just above the oil filter flange:

    o 017.jpg

    That port is internally connected to the same port used for the factory mounting position - so the operating pressure will be the same.:

    sbcoilh5.jpg
     
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  4. Steve Doc

    Steve Doc Junior Member

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    Would that factory tapped port be occupied by another switch or similarity? Because I'll be looking to use that as an option for my oil pressure switch as well. Thanks chengny.
     
  5. 73c20jim

    73c20jim Supporting Member Supporting Member

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    OK. I have oil pressure gauge sender which will be dedicated to electric oil pressure gauge. The sender will be installed under the dizzy. This is the 31 circuit. PROBLEM 1 SOLVED.

    Need to get oil pressure sender SWITCH which will be installed near oil filter. It is normally open and will CLOSE at about 10 PSI. This will allow current to flow from one prong to the other. Connecting one leg to 12V and the other to the choke will activate the choke coil to heat the coil to open the choke and then hold the choke open for the duration of your trip.

    Am I good so far on these two?????

    I am totally confused on the choke light. This is circuit 931. What is its purpose??? When should it be on????

    The top drawing seems to illustrate the GEN light not the choke light????

    Thanks.
     
  6. SquareRoot

    SquareRoot Full Access Member

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    I need to connect the electric choke on my Eddy 1406. Directions say one terminal goes to ground and the + goes to ignition "run" feed.

    Not being a smartass but, why worry about a choke light, pressure sender's, relays etc? I mean, unless it's a restoration?
     
  7. yevgenievich

    yevgenievich Full Access Member

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    The only reason to use the oil pressure switch is in the case ignition is on but vehicle not running.
     
  8. chengny

    chengny Full Access Member

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    1. I have oil pressure gauge sender which will be dedicated to electric oil pressure gauge. The sender will be installed under the dizzy. This is the 31 circuit. PROBLEM 1 SOLVED.

    Yep, sounds good. The sender alone can be easily mounted behind/under the distributor using an off the shelf 1/8" NPT street ell. Problems only begin when an attempt is made to fit both sensors to that port without using that special tee/90 fitting. I have tried several different configurations over the years - using standard pipe fittings - and didn't like any of them. My main concern was vibration and metal fatigue. To assemble a Christmas tree that would accept both sensors, required screwing a lot of fittings together. The factory fitting is one short piece, but my assemblies were really long. I was afraid that the extra length and weight might put too much strain on the first nipple where it came out of the block.

    2. Need to get oil pressure sender SWITCH which will be installed near oil filter. It is normally open and will CLOSE at about 10 PSI. This will allow current to flow from one prong to the other. Connecting one leg to 12V and the other to the choke will activate the choke coil to heat the coil to open the choke and then hold the choke open for the duration of your trip.

    Right again - except for one thing. Even without a heater, the choke will eventually open and - as long as the engine remains warm - it will stay open on its own. It is actually called an electrically assisted choke.

    From the GM service manual:

    On most vehicles, an electrically assisted choke is incorporated onto the carburetor to aid in reducing the emissions of hydrocarbons (HC) and carbon monoxide (CO) during starting and warm-up (choke-on) period. The electric assist choke is designed to vary the rate of choke opening depending on ambient temperature.

    3. On the operation/function of the choke heater and warning light circuits:

    I am totally confused on the choke light. This is circuit 931. What is its purpose??? When should it be on????

    The way the choke light is wired, it is actually a low oil pressure warning light. Seriously, who is really concerned about whether or not their choke is getting power. But if the oil pressure falls below 10 psi while the engine is running, that is a big concern. A red warning light coming on while driving is way more apt to get your attention than the gauge falling off. Matter of fact, with a base instrument cluster everything is wired exactly the same way - only the lens on the lamp is different. Instead of CHOKE, it says OIL PRESSURE.

    It should be on when the ignition switch is in RUN, but the engine has not been started. As soon as the engine fires up -and oil pressure is established - it should quickly go out.

    The circuit is not really that involved. Its just sometimes hard to follow individual wires when looking at those GM diagrams. I am making you a simplified dwg tht I will post soon - probably tonight.

    More information here:

    https://www.gmsquarebody.com/threads/sticky-choke.16551/#post-318930



    The top drawing seems to illustrate the GEN light not the choke light????

    Yeah, I'm not sure either.
     
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  9. 73c20jim

    73c20jim Supporting Member Supporting Member

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    My new (to me) gauge cluster has a choke idiot light, my compulsion says its got to work.

    Also but more important it will light with low oil pressure. So I am reading.
     
  10. 73c20jim

    73c20jim Supporting Member Supporting Member

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    Even without a heater, the choke will eventually open and - as long as the engine remains warm - it will stay open on its own. It is actually called an electrically assisted choke.

    How is is heated then???

     
  11. chengny

    chengny Full Access Member

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    I think that port was used up until the early-mid 80's in exactly the same way Jim intends to do. IOW, the sender for the gauge was mounted behind the distributor (using a simple street elbow) and the switch (used to supply voltage to the heater coil) was screwed directly into the port above the oil filter. At some point - maybe 1984 - for whatever reason, the two sensors were grouped together on that special fitting and use of that lower port was abandoned.

    Then, upon the advent of the TBI system in 1987, it was again utilized. That is where they decided to mount the oil pressure switch that was used as a backup for the fuel pump relay. The contacts in that switch were set to close at a really low oil pressure (about 4 psi). If for some reason the ECM failed to pull the FPR in (and supply power to the fuel pump), the oil pressure switch took over. When the engine was cranked over, the oil pressure came up. When it hit 4 psi, the contacts would close and power the pump.

    But having said all that, you really shouldn't trust me on historical details. The best way to determine whether the port is already used by some switch/sender/sensor is to just go look.

    But if you have a 1986 with a stock 305 engine...I think you will find that the port is free to use.
     
    Last edited: Oct 31, 2018
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  12. chengny

    chengny Full Access Member

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    By the heat radiating off the engine.


    Hey Jim, I was thinking about how to make your wiring diagram - but also about how the leads would have to be physically run. I was wondering if you had considered mounting the sender down by the oil filter and the switch by the distributor. It would make the wiring job considerably easier and you'd end up with a more professional looking result.

    Instead of three leads (LT BLU 78, DK BLU 931, PNK/WHT 350) going down to the switch, there would be just one (the TAN 31). Additionally, doing it that way would keep the switch and the choke heater close to each other. The wire runs would be shorter, which would make your engine compartment look neater (I think anyway) and reduce the possibility of damage to the leads.

    Here is how the switch and coil are interconnected. There is more to come so if it isn't clear yet, it will be:

    press_switch__CLOSED.jpg
     

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