Electrical thread, scope patterns, meter readings, electrical theory, switch/sensor

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sandt38

wheelchair class racer
Jun 20, 2012
#1
In this thread I will be discussing and showing you how do diagnose your quad's electrical systems.

I will include basic electrical theory, how switches and sensors function, what these inputs mean to your bike, I will show testing including pictures of the components being tested (at the connector), I will show/discuss multimeter readings, I will show/discuss oscilloscope testing, and patterns, and I will answer any questions regarding these systems and how they function, and why the anomalies are occurring. I will be in depth in the hopes that you can and will read the theory and get enough of an idea of how these systems function so that you will be able to figure out how and why things are behaving, or misbehaving, on your own.

This will be lengthy, but I will try to be detailed and organized. I will keep an index of sorts in this post. It will take me some time to get this whole thing done, so expect bits and pieces over a period of time.

Please keep in mind that I am not a motorcycle technician. I may not be able to answer all your questions. I am a master automotive technician with 25 years of heavy, difficult electrical and emissions diagnosis and repair. I understand what I am looking at, but I cannot tell you what the common failures are with your bike. If you have any questions you MUST follow any and all steps suggested, don't just skip over them. Nothing makes for a more difficult time of diagnosis than trusting something someone says and misdiagnosing a system because a shortcut was taken.

All these are clickable links to the post within this thread:

1) Electrical theory and how sensors switches and other devices work. How does electricity work, what is AC and DC, what is an AC Pulse generator, what is a variable resistor, and other basic theory questions...
 

sandt38

wheelchair class racer
Jun 20, 2012
#2
Basic electrical theory and how electrical devices work.

Before we get into the meat of this thread I wanted to discuss basic electricity. Electricity is simply a flow of electrons (voltage or V) that needs to be moved or pushed (by current or amps). Other important factors are the load (which is a resistance or ohms), and the common portion of the circuit (ground).

AC and DC voltages differ in important ways when it comes to automotive and motorcycle signal systems. AC voltages are alternating current. The voltage climbs above and below 0 volts in an elliptical pattern. This should be smooth and consistent. In most systems the signal is viewed by the ECM through a bias voltage. What this means is that the ECM looks at a specific voltage window, and the frequency at this voltage. Let’s say the system suggests a peak AC voltage of 10 volts. It may have a bias voltage of 5 volts. What this means is that the ECM reads the on time of the signal when it reaches 5 volts (and -5, remember this voltage goes above and below 0 volts!) to the time when it reaches that 5 volts again. DC or direct current voltages are simple, flat voltages. This is what is produced by your battery. It is simply on, or off. When viewed by an ECM it simply sees and on and off signal. You might know it as a digital signal.

AC and DC voltage signal comparisons. The horizontal black line in 0 volts, and the purple lines are simple representations of each signal:



We will ignore simple on/off switches in this section, they are simple. They will include your ignition switch, clutch switch, kill switch, light switch, brake switch, carb switch, throttle lever switch.

We will look at AC or pulse generators, DC or Hall Effect switches (if applicable), variable resistors, stators and coil outputs.

AC generators, such as the ignition switch generator, basically house a permanent magnet wrapped with a coil. The flywheel houses an opening that passes by the pulse generator that collapses the magnetic field. The collapse of the field surrounded by the coil creates a differential, and therefore a small voltage. This voltage increases in amplitude (peak voltage) and frequency as the speed of the reluctor (flywheel window) increases. No input voltage is required on these circuits, as they generate their own voltage, so they tend to be tested with the harness disconnected. You will see the listed spec as VAC or voltage AC.

DC or hall effect switches work somewhat similarly, as they use a reluctor window to create a collapse of a magnetic field, but the field is an electromagnet, not a permanent magnet. The coil is energized by an input voltage, and it collapses as the reluctor passes. You will see a simple square wave, off (input voltage) and on (ground or 0 volts). Since this type of sensor/switch uses an electromagnet it must be tested plugged in with the key in the on position. The listed spec will be VDC or voltage DC.

Variable resistors are very simple, and pretty cool. This would be your TPS and your CTS (coolant temperature sensor). A TPS uses a basic wiper resistor. You have an input voltage that enters the sensor (in our case) on the high (wide open throttle end) of the resistor. The return to the ECM is on a pickup (similar to points) on an arm that sweeps across the resistor, and returns the voltage input to the resistor and altered by the resistor to the ECM. At closed throttle we expect to see a low voltage, and as we slowly work the throttle to wide open we see the voltage increase. The CTS works through a varying resistance based on temperature. It is similar to the TPS but instead of being mechanically wiped it is thermally wiped. If we are to test these sensors under a load we will need them to be plugged in and the key turned on. While the manual dictates that we test these system resistances, we would prefer to look at them under a load. I will include the readings under load in this thread for you to have handy. In most cases the manual will list these sensor values as resistance or ohms, and they will require you to unplug them.
 

sandt38

wheelchair class racer
Jun 20, 2012
#7
Well, I guess I cannot edit after a period of time...

We will follow the trouble tree pattern outlined in the manual. I am going to be forced to add a DVOM test reading for the ignition output in a later post as I forgot to photograph the meter reading, but I did take a snapshot on the scope. My scope is always set to trigger on the down slope, so when I say the trigger voltage always assume trailing edge settings.

Underhood view, and the equipment used. SnapOn Verus oscilloscope, and Fluke 87 DVOM. The Fluke is a true RMS meter. If yours is not you may see different readings. In order to show info for everyone I did not use a peak voltage tester, but I did use my peak to peak feature to acquire the readings you see.



Fan/Ignition Control Module (CDI). The box is under the hood of your bike. I perform all testing here, contrary to the suggestions by the manual. The connectors are, from left to right, 4P (or 4 pin terminal), 8P (or 8 pin), and 6P (or 6 pin). I will refer to these connectors in the test in that manner.



Test 1 is to pull the plug and look for spark. I don't think there is any need to explain this test.

Test 2 is to test output from the Fan/Ignition control box. I chose to test the signal under the hood rather then the coil as suggested. This test needs to be done with the connector connected. I use a backprobe, you may use a pin or hat pit with a clamp. If you choose to test at the coil you can unplug the connector and test it there. To connect this properly you need to hook your positive lead to the black/yellow wire on the 6P connector and the ground to a good chassis ground. Take this reading with the key on and engine cranking. Sorry, forgot to take a shot of this connection, but when you look at the TPS test below you will get the idea of how to probe it.



The manual states at least 100 volts, so I set the scope up to a 10 microsecond per division scale, 4 volts per division scale, and a 10 volt trigger. Here you see the very quick, very powerful spike that triggers the coil. If you have no spark and have this reading, your coil is dead or your connector is corroded/damaged

Test 3 is the alternator exciter (stator) test. It is divided into 2 tests, a high and low output test. Please test both outputs!

Test 3 A First is the high output test. This is done at the 6P connector with the connector unplugged. Connect your leads from the blue/red wire and the white wire. The manual suggests specific connections (bu/r positive) but since this is an AC generator it doesn't matter. Measure this while cranking.

Ignition Exciter High (Stator High) testing at the connector.



Scope reading of the exciter. Since the manual claims ~35 volts I went with 10 volts per division and 40 miliseconds per division with a trigger at 10 volts.



Meter reading. Why is it so significantly different? The signal is extremely fast and the meter cannot pick up outside it's usable range. To illustrate, I plugged my scope into a wall socket, and my peaks were at 165 volts. My meter claimed 119 volts AC.



I would love to be able to tell you what a failure reading would be with a DVOM, but I cannot. It is not stated in the manual without peak testers. Since both the high and low pickups show roughly 1/2 the measured peak voltage I will guess that we can assume 1/2 of the manuals stated minimum voltage is the failure point. But the scope displays the peaks outright, so there is no need for guesswork there. If this test fails, replace the stator.
 

sandt38

wheelchair class racer
Jun 20, 2012
#8
Test 3 B is the low stator output. This is done at the 6P connector with the connector unplugged. Connect your leads from the blue wire and the white wire. The manual suggests specific connections (bu positive) but since this is an AC generator it doesn't matter. Measure this while cranking.

Ignition Exciter Coil (stator) Low testing at the connector.



Scope reading of the exciter. Since the manual claims ~15 volts I went with 10 volts per division and 40 miliseconds per division with a trigger at 10 volts. Basically I did not change my high side readings to show a comparison of the 2 signals.



Meter reading. Here again it is displaying 1/2 the actual peak voltage of the scope.



I would love to be able to tell you what a failure reading would be with a DVOM, but I cannot. It is not stated in the manual without peak testers. Since both the high and low pickups show roughly 1/2 the measured peak voltage I will guess that we can assume 1/2 of the manuals stated minimum voltage is the failure point. But the scope displays the peaks outright, so there is no need for guesswork there. If this test fails, replace the stator.

Test 4 is the Ignition Pulse Generator peak voltage test. This signals the time when the coil is triggered to fire. I have seen a Scrambler where this pick up got hit by debris and knocked it out of adjustment. My suggested reading was 3.3 volts and we saw ~.9 volts. The signal was clean, which indicated the sensor appeared to be good (a shorted coil inside the pickup would alter the signal), but it was not being triggered correctly. We opened it up and reset the gap and fixed the bike for free. This actually gave me the idea to do this thread. Keep in mind, AC signal generators that have specified gaps that are exceeded will show clean patterns with low voltages!!!

Again, this test is done with the key on and engine cranking. Disconnect the 8P and 6P connectors. Connect your leads to the blue and yellow wire in the 8P connector, and the green/white wire in the 6 pin.



Since the manual called for .7V minimum I set my voltage to 1 volt per division, my time base to 40ms per division and my trigger at .7V.



Oddly the specified minimum voltage for this test showed to be passing on the meter:

 
Apr 13, 2012
#10
Now this is what a forum is for! Education and sharing of knowledge. Not childish bitching, moaning, and fighting.

This is very appreciated Sandt38, thank you!
 

sandt38

wheelchair class racer
Jun 20, 2012
#11
Test 5 is the TPS test. This is simply a measurement of the throttle plate opening. Honda gives us a spec in resistance. IMO this is not always a good test. The computer doesn't give a shit what the resistance it, all it cares about is the returning signal voltage.

However, as the manufacturer states I will first show testing using resistance. Test with your ohm meter set to 40Kohms across the grey/black and grey terminals on the 8P connector with the connector unplugged and the key off. The spec shows 4-6Kohms, but neglects to state when this is taken. This is an open throttle measurement.



Closed throttle reading. This is .8 Kohms



Slowly sweep the throttle lever and you will see the resistance slowly climb to this reading:



I prefer to test with the key on. Connect the connector, then backprobe the grey wire at the 8P connector and connected my ground to the chassis ground. Slowly sweep the throttle and watch the sweep. I set my scope to 1 volt per division and 1 second per division.



You can set your meter to read this by choosing the DC Voltage scale and either a 4 or 40 volt scale. Your readings will be exactly the same as you see on the scope, slowly climbing from ~.7 VDC at closed throttle to ~4 VDC at wide open throttle.
 

Bryce

Active Member
May 1, 2013
#14
Now this is what a forum is for! Education and sharing of knowledge. Not childish bitching, moaning, and fighting.

This is very appreciated Sandt38, thank you!
I couldn't have said it better, Agreed 100%!! Thanks for putting this together Sandt38!!