Post Reply 
 
Thread Rating:
  • 0 Votes - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
finding put pos and neg on vent solenoid wire
07-14-2017, 08:56 PM
Post: #1
Question finding put pos and neg on vent solenoid wire
hi I got a link here on the bottom an I am trying to get help with trying to find out which vent solenoid terminal is negative and positive the link doesn't exactly say how to find out http://www.thesmokemachine.com/TechTip%2...lenoid.pdf


i also can't find the vent solenoid (vent valve) anywhere online, as I think its called a evap shut-off valve
Find all posts by this user
Quote this message in a reply
07-14-2017, 10:34 PM
Post: #2
RE: finding put pos and neg on vent solenoid wire
I believe you are over thinking this.

If you have a meter, then pull the plug and connect the meter to the harness side using a DC volts scale. Turn the key on and see if you have juice. (12 volts or so) If the meter reads backwards then reverse the leads. The red lead will tell you which wire is positive, if you really need to know.

Using the ohms scale on your meter check the solenoid side and you will probably see something around 100 ohms, maybe a slight variation. That only means it's good electrically. You can probably get it to cycle / click with a battery... like a 9 volt. Sometimes they get gummy so try a bit of carb cleaner through the hose connections and test again.

Let us know how you make out.
Find all posts by this user
Quote this message in a reply
07-19-2017, 06:42 PM
Post: #3
RE: finding put pos and neg on vent solenoid wire
(07-14-2017 10:34 PM)Rupe Wrote:  I believe you are over thinking this.

If you have a meter, then pull the plug and connect the meter to the harness side using a DC volts scale. Turn the key on and see if you have juice. (12 volts or so) If the meter reads backwards then reverse the leads. The red lead will tell you which wire is positive, if you really need to know.

Using the ohms scale on your meter check the solenoid side and you will probably see something around 100 ohms, maybe a slight variation. That only means it's good electrically. You can probably get it to cycle / click with a battery... like a 9 volt. Sometimes they get gummy so try a bit of carb cleaner through the hose connections and test again.

Let us know how you make out.

Thank you for the response, a bit confused but getting the idea somewhat.

I am guessing the basic volt meters are DC volt meters?

So if the red lead tells me which one is positive then why would I need the negative?

Does checking the ohms mean putting it on a certain setting on the meter and putting the 2 leads in the connection, regardless of which side is being poked.

I think I have seen 1 person use 9v batteries to activate something but there was no explanation on what side he is touching and what not
Find all posts by this user
Quote this message in a reply
07-19-2017, 10:47 PM
Post: #4
RE: finding put pos and neg on vent solenoid wire
What you need for this test is a DC volt meter that also has an ohms scale. Most meters (typical from Radio Shack, etc) have the ability to read AC, DC, and ohms on a variety of scales. In order to read any electrical circuit you must complete the circuit using the meter. IOW, think of the power traveling in a loop so out one lead, to the component you are reading, then back into the other lead of the meter. You wouldn't connect one cable on the car battery and expect it to work, right?

On the harness side, you must complete the circuit as well so using both leads with the key on it will read battery voltage. If it's al old fashion meter with a swing needle it will try to swing the wrong way if you have the leads backwards. If it's a digital meter it will show a "-" sign if the leads are reversed. This how you will know which side of the plug is positive. (make a note or mark at this point)

On the solenoid side of the plug, doing an ohms reading probably doesn't matter which way the leads go because all you are doing is establishing that the electrical continuity is ok, but it may make a difference when you add power to see if the solenoid clicks or actually opens. Reason being is some of these valves have a diode in the circuit to prevent voltage spikes. If you like, try to take a meter reading both ways and also try powering it both ways just to be sure.

BTW, these solenoids are cheap, especially if gotten from Rock Auto or Amazon.com. Doing a proper diagnosis is a royal pain even for us old pros!
Find all posts by this user
Quote this message in a reply
07-23-2017, 09:38 PM
Post: #5
RE: finding put pos and neg on vent solenoid wire
(07-19-2017 10:47 PM)Rupe Wrote:  What you need for this test is a DC volt meter that also has an ohms scale. Most meters (typical from Radio Shack, etc) have the ability to read AC, DC, and ohms on a variety of scales. In order to read any electrical circuit you must complete the circuit using the meter. IOW, think of the power traveling in a loop so out one lead, to the component you are reading, then back into the other lead of the meter. You wouldn't connect one cable on the car battery and expect it to work, right?

On the harness side, you must complete the circuit as well so using both leads with the key on it will read battery voltage. If it's al old fashion meter with a swing needle it will try to swing the wrong way if you have the leads backwards. If it's a digital meter it will show a "-" sign if the leads are reversed. This how you will know which side of the plug is positive. (make a note or mark at this point)

On the solenoid side of the plug, doing an ohms reading probably doesn't matter which way the leads go because all you are doing is establishing that the electrical continuity is ok, but it may make a difference when you add power to see if the solenoid clicks or actually opens. Reason being is some of these valves have a diode in the circuit to prevent voltage spikes. If you like, try to take a meter reading both ways and also try powering it both ways just to be sure.

BTW, these solenoids are cheap, especially if gotten from Rock Auto or Amazon.com. Doing a proper diagnosis is a royal pain even for us old pros!


so I am guessing that for the picture for steps 1-4 (putting the black lead to a ground) is not accurate, I had a feeling that your way is correct in finding the polarity since I saw a youtube video on what you mean before that response.

which is this video https://www.youtube.com/watch?v=xoUHbf_bRxw

now when you mean doing a reading and then powering it, do you mean do a reading with the car off then doing a reading with the car on?

solenoid side meaning the wire harness that connects to the valve like in this youtube video picture https://youtu.be/p9wRD_Dwt8g ?

I might skip the ohms part since i get confused easily

also was thinking if this idea would work since the first link in my first post tells me to touch the car battery to close the vent solenoid maybe the valve will close if i touch a regular AA battery or 9v battery and get the black lead to touch the negative side of the AA or 9V http://www.ijdmtoy.com/webpage/installat...ster-3.jpg
either that or maybe I can get another car nearby and use that battery since the terminals maybe short, depending where the evap valve is located, but since I have a 95 volvo 850 turbo the valve might be on the drivers side

I wouldn't say old pros but True Pros
Find all posts by this user
Quote this message in a reply
07-23-2017, 11:43 PM (This post was last modified: 07-23-2017 11:45 PM by Rupe.)
Post: #6
RE: finding put pos and neg on vent solenoid wire
now when you mean doing a reading and then powering it, do you mean do a reading with the car off then doing a reading with the car on?

===================================

Yes, connect the meter to the harness side of the connector then turn the key on to see if it registers 12 volts. (or similar battery voltage, 12 - 13 volts) It may only show voltage for a few seconds so pay attention.

Do not try to test with an AA battery, the voltage is too low. Use a 9 volt battery or another car battery with jumper leads. The nice thing about using a 9 volt battery is you don't run the risk of smoking wires if you short something out, although the solenoid click will be fairly faint due to the low power availability.

The only reason to do an ohms test is to verify you have a nominal value between say 50 and 200 ohms, which is typical of small solenoids. Basically you just want to know that it's NOT an open or shorted circuit.

If this is getting over your head than perhaps it's time to bring it to a shop.
Find all posts by this user
Quote this message in a reply
Post Reply 


Forum Jump:


User(s) browsing this thread: 2 Guest(s)