bypassing a solenoid-replacing with an equal load

Discussion in 'General Electronics Chat' started by greeneclipse, Dec 8, 2005.

  1. greeneclipse

    Thread Starter New Member

    Dec 8, 2005
    5
    0
    Hi all,


    I have a couple of emissions solenoids on my car that i would like to bypass. I can unplug them, but then i get a check engine light.

    I've gotten suggestions to replace the solenoid with an "equal load", but i don't have a clue as to what i should do.

    If it helps any, the solenoids have two prongs, and each solenoid has a 100ohm resistance.

    Again, I have no idea where to start with this task.

    -thank you all in advance for your help


    edit: i can post pictures of them if that would help
     
  2. Brandon

    Senior Member

    Dec 14, 2004
    306
    0
    put in a 100 ohm resistor in its place (prob want 1W resistor or larger to handle current and additional heat from inside the engine)
     
  3. greeneclipse

    Thread Starter New Member

    Dec 8, 2005
    5
    0
    cool...

    have a couple more questions to ask if you dont mind...

    1)i measured the solenoids again and this time the reading came out to be around 93ohms for one and 87ohms for another.

    can the resistance be variable like this? Also, could you just tell me what/how i should set my ohmeter when i measure it. ( kinda my first time using one )

    2) Would this resistor be ok (its a 100ohm 10W) or is it overkill.

    http://www.radioshack.com/product/index.js...rentPage=family

    and one more thing...

    3) does it matter which way i were it up ? and is there a certain way to wire this up?

    thanks again for helping me out
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Hi,

    If you want to get closer, try a 91 ohm resistor. They aren't polar, but make sure things are well waterproofed.

    You may continue to see lights, as the solenoids may have associated sensors which won't see what they expect with the function disabled.
     
  5. Brandon

    Senior Member

    Dec 14, 2004
    306
    0
    Actually, those would be perfect.. just perfect.

    Don't worry about the actual reading from the meter. They are 100 Oahm Solenoids. The fact they read not 100 is just the magnet, the coiling, etc. 100 Ohm is the designed spec.

    But those resistors, perfect, They are wire wound resistors, just like solenoids, save its a resistor. They are not tiny so you can work with them easy, they are sturdy and work over a large temp range, ideal for under the hood. As beenthere pointed out, make sure they are waterproof, as wire wound, if they short it will cook. Mayby find a putty epoxy which can handle high temp. I've seen this quick setting epoxy putty at home depot. Just mash, mix, place and its hard as steel in about 20-30 minutes.

    With the ohm meter, you will see ranges done with whole numbers, it will be something like 2, 20, 200, 2k, 20k, 200k or something similar. If you are on say 20k, or 200k setting and you see 2.1 that means you have 2.1k ohms. If you have the setting on 20 or 200 and you see 2.1, it means you have 2.1 ohms, not 2.1k. if you set it on a number and you see 1____ (bunch of spaces) or something odd, it means the resistance is higher than your setting and move your setting up a notch. Got it?
     
  6. greeneclipse

    Thread Starter New Member

    Dec 8, 2005
    5
    0
    ^^^^^^^


    got it....i checked them with it set on 200 and the readings i got varied from around 70-90Ω

    i guess the the link i put up doesnt work, but the exact resistors are:
    100 ohm 10W 5% Wirewound Resistors

    How should i wire these up? The solenoids have the male prongs that the factory female harnesses connect too.

    also, should i cover the entire resistor in the epoxy compound? won't this make it heat up even more?


    i tried to attach a couple of pics. but it wouldn't let me.

    thanks
     
  7. Brandon

    Senior Member

    Dec 14, 2004
    306
    0
    Yeah, I went to the web site and looked at them before from the link. Seen them before in the store, been in Radio Shacks a fair bit when I need a quick part.

    No polarity in a resistor. Just connect the each end of the resistor to a lead in the femal harness on the body. Doesn't matter which direction. Just bridge the female connector with the resistor. If you can find a male connector for the solenoid, you maybe can solder the wire leads from the resistor into the pins and just plug it in. Will make for easy switching if you need it.

    You can cover the entire resistor. Since its a 10 watt resistor it won't heat up that much due to the low voltage. Assuming the solenoid runs off of a 12v supply and at 100 ohms, thats only 1.44 Watts.
     
  8. greeneclipse

    Thread Starter New Member

    Dec 8, 2005
    5
    0


    do i have to worry about finding which female side/pinout is the ground......do i even need to worry about a ground?

    and can i just connect them wire or quick taps,or do i need to solder them?
     
  9. Brandon

    Senior Member

    Dec 14, 2004
    306
    0
    resistors have no polarity so you can connect it in any direction. Doesn't matter which side is ground to a resistor, all it does is resist current flow.

    Connect how ever u want, just make sure how ever you connect it up it won't vibrate off while driving.

    Your just doing a swap-a-roo, like Indiana Jones. Tried to put a rock the same weight as the gold statue, you doing no different.

    All you are doing is faking out the circuit, nothing complicated about it. Electrical Engineering is a 'black box' engineering type. You DON'T CARE what is in the box, just what the boxes specs are. If 2 black boxes specs are very similar, then to the circuit they are connected to, they will be nearly the same EVEN IF THE BLACK BOXES ARE TOTALLY DIFFERENT INSIDE.

    This is what your doing. All the car knows is that it gives juice to a load thats about 100 ohms, it just happened to be a solenoid. You put a 100 ohm resistor and to the car, it sees nearly the same thing. Makes no difference they are not the same parts.

    You put a 135 ohm resistor in the place of a 100 watt light bulb and to the lamp, nothing has changed. Its giving juice to something at about 130 ohms and pushing out 100 watts.

    If it looks like a duck, sounds like a duck, you can use it replace any other similar duck.
     
  10. greeneclipse

    Thread Starter New Member

    Dec 8, 2005
    5
    0
    makes prefect sense...

    just out of curiosity.....does the load change at all when the solenoid is open or closed? These are vacuum solenoids that open and close when signaled.

    I understand what you're saying....im just trying to learn how things like this work.

    thanks for all the info. It's goin to make this whole project a lot easier.
     
  11. Brandon

    Senior Member

    Dec 14, 2004
    306
    0
    it will change slightly due to the magnetic field which gets generated when it first switches openor closed, but once it been open or closed for a period of time, it will stabilize and return to it typical values.

    Only when there is a change (i.e. when its turned from off to on, or on to off) will a solenoid appear different than a resistor but at soon as the magnetic field has been generated or discharges from the coils and isn't changing any more, its just a resistive load.

    Basically, resistors don't do anything special. They act the same at all time, they resist. Solenoids (a form of inductor) react when there is a change in the circuit. If nothing is changing its almost like the inductor isn't even there, just its resistance in the windings of wire, i.e. the 91 ohms you measured, but as soon as you flip the switch, the inductor continues to try to do what it was just doing, due to the magnetic field or lack there of and resists the change. Kinda like a pipe of water. You turn the faucet off but the water keeps going.. Could also think of it like a siphon. the inductor's (solenoids) magnetic field continues to make the current flow even when you turn it off until it runs out of magnetic field.

    Nothing you need to worry about with this in any way, shape, or form. Just FYI.
     
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