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You can apply voltage to it and see if it "clicks", and you also need to check continuity from the battery in to the starter output terminals when it "clicks".
This does not however let you know if there has been a build up of internal resistance from arcing that would limit power going to the starter.
 

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Your solenoid will probably look something like the one in the pic below except for the type of fuse. The stud terminals on the top are for the switch contacts and the small terminals in the "box" are where the connector from the wiring harness plugs in. To test the solenoid you need to connect an ohmmeter across the stud terminals and when you apply voltage to the "A" terminals (+ on one, - on the other) the solenoid should click and the resistance between the studs should be zero ohms. (you may need to reverse the + and - to make it work)
202223


BTW: Welcome to the forum. Please add your location to your profile and your bike's model and model year (NOT year first registered) to your signature so that you don't have to remember to tell us every time and we don't have to keep asking when you forget (see Forum Settings link in my signature).

And welcome to the world of antique vehicle ownership (they own us, not the other way around). Your bike is about 4 decades old and the Previous Owners may or may not have done the maintenance necessary to keep it safe & reliable so it is highly recommended to download the Factory Shop Manual for your model (available through the CX Wiki - link in my signature) and go through all of the service procedures, regardless of whether your bike has reached the specified mileage.
I also recommend looking on all rubber parts with suspicion because rubber does not age gracefully. Check the date codes on your tires and replace them if they are over 5 years old no matter how good they look & feel because old rubber simply cannot flow around the irregularities in the asphalt well enough to grip, especially if it is cool or wet. If your bike still has the original rubber brake line(s) (should be replaced every 2 or 3 fluid changes = 5 or 6 years) I recommend shopping for modern stainless braided ones (they last practically forever and double the life of the fluid).
 

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Discussion Starter #4
Thanks to you guys for expanding on the subject of starter solenoid (relay) testing.
The starter cranks with the wrench test. The voltage to the solenoid is 11.4 when starter button is pushed. Battery terminals read 12.4 volts. There is no click from solenoid upon pushing start button. and a friend said to check solenoid ground to starter. Connection is good. If I remove cable and check it as ok, then I have a bad solenoid. Is that correct?
 

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There is no "solenoid ground to starter". Current flows from through the positive battery cable from the battery to the B stud on the solenoid, through the solenoid's contacts (when the solenoid is actuated) and from the solenoid's M stud through the starter cable to the starter motor, which is connected to ground through its mounting points. Depending on which model you have (you still haven't told us) the battery negative cable (sometimes referred to as the ground cable) is connected to either a stud on the frame or is sandwiched between the starter motor and its bracket to complete the circuit back to the battery.

"The voltage to the solenoid is 11.4 when starter button is pushed" is meaningless if you don't tell us which of the 6 terminals on the solenoid you measured the voltage at.

There are several reasons why a solenoid that is functional might not click when you press the Start button. Start by measuring the voltage between the A terminals while you press Start.
 

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Discussion Starter #6
There is no "solenoid ground to starter". Current flows from through the positive battery cable from the battery to the B stud on the solenoid, through the solenoid's contacts (when the solenoid is actuated) and from the solenoid's M stud through the starter cable to the starter motor, which is connected to ground through its mounting points. Depending on which model you have (you still haven't told us) the battery negative cable (sometimes referred to as the ground cable) is connected to either a stud on the frame or is sandwiched between the starter motor and its bracket to complete the circuit back to the battery.

"The voltage to the solenoid is 11.4 when starter button is pushed" is meaningless if you don't tell us which of the 6 terminals on the solenoid you measured the voltage at.

There are several reasons why a solenoid that is functional might not click when you press the Start button. Start by measuring the voltage between the A terminals while you press Start.
I am slow, and do appreciate the help Bob. The bike is a Honda CX500C, 1982. Voltage between the solenoid large terminals ignition on is 11.9. No change when starter button is pushed. Voltage from the hot (red) terminal of solenoid is 11.9. My voltmeter red probe goes to that terminal. My black probe goes to the starter mounting bolt .
before and after pushing starter button there is no voltage change. When I connect my voltmeter red probe to the black solenoid to starter side I get no voltage reading before or after pushing the starter button. My black voltmeter probe remains connected to the starter mounting bolt for this test.
On this model, there are 2 wires that come from the wiring harness. Thus. I have 2 large solenoid terminals. And a plastic connector that holds the 2 wires from the harness. I do not have 6 terminals, only 4. The voltage reading I initially disclosed was the reading between the 2 small wires from the harness inside the plastic case when I disconnected them. Connected them to my volt meter and got a voltage reading of 11.4 when I pushed the starter button. Initial reading there was 0 before pushing the starter button.Also. my battery is grounded to a frame stud.
 

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Yes, IIRC only the later CX500C models have the battery negative connected to the stud.

The information I have indicates that the '82 CX500C uses the same solenoid as the GL500, which I know is the one with the 4 terminal connector (similar to the pic I posted earlier, except for the type of main fuse). Perhaps someone with an '82 C can tell us if that is correct.

If you do have the earlier type of solenoid and there is voltage across the terminals for its coil it should click when you push the button.
 

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GL500 and CX500 use a slightly different starter solenoid. I think you'll want to back probe the red/yellow (?) wire and see if you have power between there and a ground when you press the starter button. From what I remember, the outgoing wire (green/red?) also hooks into the neutral switch and clutch lever switch, so you'll have to make sure those are working as well, and do this testing on your center stand, you don't want an inadvertent path to ground if you're in gear!
It also seems like you've got some corrosion problems with that voltage drop, so you'll probably want to back probe all the way through the system to see what's causing the drop(s). I don't know what the trigger voltage is for these solenoids, but I've seen some solenoids that won't trigger at less than 12V.
 

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Discussion Starter #9
Please tell me how to test a neutral safety switch. My neutral light is on and the bike does not start in neutral, or with the clutch lever pulled in. Thanks
 

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Connect multimeter leads to the neutral switch terminal and ground with the meter set to measure resistance. The meter should indicate open circuit, infinite resistance, when the transmission is in any gear and continuity when in neutral.
 

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If the neutral light is on the neutral switch is likely working. The easiest way to check it is to put the transmission into gear and if the light goes off the switch is working.

As you already know, the starter motor is supposed to work if the transmission is in neutral or if the transmission is in gear with the clutch disengaged but not when the transmission is in gear with the clutch engaged. Two circuits are involved in that:
1) The starter disconnect switch (in the clutch perch) interrupts the starter solenoid circuit between the solenoid and ground, preventing it from being energized unless the clutch lever is pulled.
2) The neutral switch interrupts the neutral light circuit between the light and ground.

The diode is connected between the neutral light circuit and the starter solenoid circuit so that the neutral switch bypasses the starter disconnect switch but the starter disconnect switch has no effect on the neutral light.

  • If the diode is missing or has failed in open circuit mode the starter will only operate when the clutch lever is pulled.
  • If the diode has failed in short circuit mode the neutral light will come on whenever you pull the clutch lever.
But I don't think your problem is in that area.

Did you download the FSM yet? Go to the CX Wiki right now, get the FSM if you haven't already and get the colour wiring drawing for your model and the Honda Wire Color Codes chart. They are essential for figuring out what is going on in the bike's wiring.
Once you have the drawing find the box that represents the solenoid. Inside the box you will see the contacts and the coil (the squiggly part - it represents multiple turns of wire). If you trace the wires from the coil, one will eventually connect to the battery positive and the other to ground.

Put the bike on the centrestand (It is easier to get at things), the transmission in neutral and turn the kill switch to OFF (this will allow the starter motor to run but no spark so it won't start). You will need 2 test leads (wire with alligator clip on each end) or if you don't have those a couple of pieces of insulated wire about 1-2 feet long with the insulation removed from about 1/2" on either end can be used if necessary.
- Start by unplugging the connector for the solenoid's coil. Use one test lead to connect the wire that normally grounds through the wiring directly to ground. Connect the other test lead to the wire that normally connects to power and touch its other end to the battery's positive terminal.
--- If the solenoid clicks and the starter motor runs the solenoid is OK.
--- If the solenoid doesn't click or the starter motor doesn't run the solenoid is probably the problem.
- If the solenoid's is OK plug the connector in again and use a test lead to connect that wire normally connects to ground through the wiring directly to ground and press the Start button.
--- If the starter motor runs it does you know that the problem is between the solenoid's coil and ground so start checking all of the connections in that part of the wiring.
--- If the starter motor doesn't run verify that the circuitry you bypassed is working by removing that test lead, connecting a test lead to the wire that normally connects to power through the wiring and touching it to the battery's positive. (If the starter runs the ground circuit is probably OK and the problem is between the solenoid's coil and positive)

Once you have done that it is a matter of following the diagram to figure out where there are connections and switches on the bike and making sure they are clean and working (this would be a good time to mention that you should never clean any electrical connection or switch with anything except real electrical contact cleaner).
 

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Discussion Starter #12
Really appreciate all. I followed instructions of previous post, so I will go there first. I found it interesting that some solenoids do not click. And some will not function with less than 12 volts.
I connected the red/white small wire that goes to the solenoid to ground and pushed starter button. Reading was 11.64 volts.
I checked clutch switch . With clutch out there was no continuity. With clutch in there was ccontinuity.
I have no start in neutral. Neutral light on. I pull clutch in in neutral, still no start. I put bike in gear. Neutral light goes out, then I pull clutch in while in gear, still no start.
Next item. Wiring to clutch switch. I test for voltage between the two terminals. No voltage reading with ignition on should there be a voltage reading at the clutch switch with the ignition on?
Lastly. I will make the checks that Sidecar Bob suggested, as well as download FSM for color codes. And yes, 3 necessary items for this project are: contact cleaner and Penetrant and patience. I possess larger amounts of the first two items. Still working on the third but improving in my efforts!
 

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Familiarize yourself with the drawing and you'll be able to figure out whether there should be voltage on any wire relative to any other.

BTW: Don't forget to add the bike's model & year to your signature and your location to your profile. There may be a member nearby who can help you figure this stuff out in person....
 

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Discussion Starter #14
Got the wire diagram. I have already committed much of the front items to memory. Now going to follow your helpful instructions regarding solenoid and related.the website is much more complex than Rob from England had up some years ago. How do I access settings to enter the info you are requesting? Thanks Bob and all the other advisers.
 

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Discussion Starter #16
Ok Sidecar Bob. When I connected the wires as instructed I got arcing only at the battery positive tetminal. No click. No cranking. I will be replacing the solenoid. Crossing my fingers. Thank you.
 

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Discussion Starter #19
CX500C, 1982. New starter solenoid from ebay. Now cranks like new. This bike will live now. And not get parted out. Thanks all.
 

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The diode is connected between the neutral light circuit and the starter solenoid circuit so that the neutral switch bypasses the starter disconnect switch but the starter disconnect switch has no effect on the neutral light.

  • If the diode is missing or has failed in open circuit mode the starter will only operate when the clutch lever is pulled.
  • If the diode has failed in short circuit mode the neutral light will come on whenever you pull the clutch lever.
Just an aside, here.
There is a third failure mode. The neutral light on the Grub works normally, but the starter will turn with the transmission in gear and the clutch engaged. I'm not certain of the cause, but have assumed a diode failure,
Some time, years ago, I bought a replacement and the problem stopped for a while. It's now intermittent, but increasingly frequent. And I can't find the new diode.
 
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