Stator Papers 4

The Fault Finding Chart

Originally by Peter Huppertz and Ritzo Muntinga.
Major updates by Posplayer (Jim Moore)

The object is to present you with a clear testing scheme to determine which component in your charging system is at fault. All too often, someone (yes, that includes quite a few dealers as well) will come to the conclusion that the stator has died, and thus replace the stator, and leave it at that. Chances are that you'll have a charging problem again soon, leading to the conclusion that All Stators Suck, whereas the real reason might be a defective regulator/rectifier.

Before reading on, you might want to take a look at The Stator Papers 1: A Primer on GS charging systems, which tries to explain the theory.

Warning!

This fault-finding chart assumes that the user has knowledge of the basics of electricity ( you should know the difference between voltage, current, resistance, etc.), and some knowledge about electrical systems on motorcycles in general. If you do not have this knowledge and experience, find someone that has and let her/him use these charts and check the charging-system on the bike in order to prevent structural damage to you, the bike, and in the worst case the house as well.

The use of this fault-finding chart is entirely at the risk of the user.

Scope

This testing scheme has been adapted to fit all air-cooled Suzuki GS models with a standard charging system.

Get On With It

OK, after dealing with these general issues, let's get underway.

  • First of all. fully charge the battery. If the battery is not healthy AND fully charged, you are likely to get unpredictable results using this fault-finding chart.You could just replace it with a battery off another motorcycle that has a good functioning charging-system. Using an acid-meter, verify that the battery is still healthy. If you haven't got one, any garage can do this for you.
  • Use an accurate digital multimeter. The $15 filler station variety will not do, but if you know anything about electrics, that's old news for you.
  • Throughout this procedure, the abbreviation R/R is used to designate Regulator-Rectifier because it's a tongue-twisting long term. All diagnoses are against a yellow background.
Phase A
Test Charging System And The Connections To The Battery
Step #1 - Measure Charging Voltage
Switch the multimeter to DC Volts. Switch the range to 20 or 50 V. Connect the multimeter leads to the battery terminals. Start and rev the engine up to 2500 RPM. Check that the battery voltage increases from 12.8v to over 13.5v with RPM.
Higher than 13.5v?
right arrow
Rev the engine up to 5000 RPM. Check the reading on the meter.
Between 14.0v and 14.8v?

(Suzuki manual says 14.0v-15.5v but that is too wide.)
right arrow
Charging system perfectly OK. But if you have not done it, perform Steps #2 & #3 to check connections.

Disconnect most of the connections on the bike and spray them with contact cleaner or WD40. This could prevent problems in the future.

If you have done all three steps and you are charging over 14.8v then look into replacing the R/R. Go to Phase C.
Lower than 13.5v?
If you previously completed Step #2 & #3 and you still have low output then proceed to Phase B to check stator output.
down arrow
 
Higher than 14.8v or lower than 14.0v?
down arrow
 
 
Step #2 - Measure Positive Lead Voltage Drop
Continue running the engine at 5000 RPM and connect the black multimeter lead to the battery(+). Connect the red multimeter lead to the RED output wire of the R/R. Leave the R/R connected to the bike. Check the reading on the meter.
More than 0.25v?
right arrow
Bad connection in the positive lead from R/R(+) to battery(+). Check the entire lead (suspect the connectors as well as the fuse-box and fuses). Good connections are extremely important in this high current lead.

Solve the problem and move to STEP #3.
Less than 0.25v?
down arrow
 
 
Step #3 - Measure Negative Lead Voltage Drop
Continue running the engine at 5000 RPM and connect the red multimeter lead up to the battery's negative pole (-) Connect the black multimeter lead up to the negative output of the R/R (BLACK/WHITE), but leave the R/R connected up to its leads on the bike. If you can't find a negative output wire, then the casing of the R/R is normally the negative lead to the frame. Check the reading on the meter.
More than 0.25v?
right arrow
Bad connection in the negative lead from R/R(-) to battery(-). Check the whole lead to the battery(-). If the R/R doesn't have an output lead but uses the case as connection to the frame, clean the area where it is bolted and use new screws. Also check the connection between battery(-) and frame. Also suspect the plate on which the R/R is mounted (sometimes it is rubber mounted and uses an extra cable from this plate to the battery(-) or frame). Disconnect all suspect terminals and clean.

Best solution: Add an extra wire to connect the R/R straight to the battery(-).

Solve the problem and return to Step #1.
Less than 0.25v?

If you have previously completed Step #2 and #3 and you still have less than 13.5v at 5000 RPM then proceed to Phase B to check stator output.
down arrow
 
 
NOTE: a 0.25v limit was placed on the R/R to battery connections. This is desirable but not absolutely necessary. Voltage as high as 0.5v may be tolerable. Just realize that the total of the two voltage drops will take away from your output charging voltage at the battery.

For example, if the R/R is (internally) programmed to output 14.5v and you have a 0.25v drop on the negative leads and a 0.50v drop on the positive leads, then your output voltage at the battery will only be 13.75v = 14.5v - 0.25v - 0.50v. A Honda regulator with a 6th sense wire can compensate for this but it is still good to keep the voltage drops as low as possible.
Phase B
Stator Tests
Take Notice of the Following
On the GS models, Suzuki used different colours for the three output wires of the stator. They are the only manufacturer doing this. The only conscious reason for this would be a desire to cause confusion, because the output of all the three wires is the same. The colours on the wires from the stator are : Yellow, White/Blue and White/Green. On the R/R we're talking : Yellow, White/Blue and White/Red. JUST THINK THEM ALL BEING YELLOW, and then go on with the checks below.
Stop the engine. Disconnect the wires emerging from the stator. Switch the multimeter to Ohms, the lowest range on the meter. Connect the multimeter leads BETWEEN two of the three yellow wires. Check the reading on the meter. Switch one of the multimeter leads to another of the three wires and check the reading again. Switch the other multimeter lead to another of the three wires, and check the reading again. You need to take three readings.
Are any of the readings lower than 0.5 Ohms or higher than 2 Ohms?
right arrow
Bad News! Stator is at fault. Replace the stator and return to Phase A!
Are all readings are within 0.5 to 2.0 Ohms.
down arrow
 
 
Connect one of the multimeter leads to one of the three yellow wires. Connect the other multimeter lead up to the engine casing. Check the reading on the meter. Do this with the other 2 yellow wires and record the readings. Make sure the connection to the casing is a good one!
Are any readings between 100 Ohms and zero Ohms?
right arrow
Bad News! Stator is at fault. Replace the stator and return to Phase A!
Infinite resistance (no reading at all, or OL in the display)?
down arrow
 
 
Switch the multimeter to AC-Voltage (Range at least to 100 Vac). Make sure you DON'T switch it to DC-Voltage (=DCV or Vdc). Connect the multimeter leads between two of the three yellow wires emerging from the stator. Start the engine and rev it up to approx. 5000 RPM. Check the reading on the meter. Switch one of the multimeter leads to another one of the three yellow wires and check the reading again. Connect the other multimeter lead to the last of the three yellow wires, and check the reading again.
Are the three readings not equal, or is one of them below 60 volts (AC)?
right arrow
Bad News! Stator is at fault. Replace the stator and return to Phase A!
All three readings are equal and all are higher than 60 Volts (AC)
down arrow
 
 
Continue revving the engine at approx. 5000 RPM. Leave the multimeter set to AC-Voltage (Range at least to 100 Vac). Connect a multimeter lead to one of the three yellow wires emerging from the stator and connect the other multimeter lead to the battery(-). Check the reading on the meter. Switch the multimeter leads to another one of the three yellow wires and check the reading again. Connect the multimeter lead to the last of the three yellow wires, and check the reading again.
Are any of the three readings not equal to 0 volts (AC)?
right arrow
Bad News! Stator is at fault. Replace the stator and return to Phase A!
All three readings are equal to 0 Volts (AC)
down arrow
 
 
Take Notice of the Following
The testing done under this phase is checking the stator under no-load conditions. Sometimes issues with insulation breakdown in the stator will only show up when placing a electrical load on the stator. If you wish to build a dummy load for testing of the stator then check out Posplayer's document on how to build one in the document located here.
Test Phase C - R/R Tests
NOTE: this test will only work on original R/R's or those using a Shunt-type design. Try performing the Quick Test if you haven't already.
Disconnect the R/R from the bike. Switch the multimeter to the diode test position. Connect the RED multimeter lead to the RED positive output wire of the R/R. Connect the BLACK multimeter-lead to one of the yellow wires. Check the reading. Repeat this procedure for the two other yellow wires.
Are any of the readings 1.00v or lower on any of the three tests?
right arrow
Different Bad News! Regulator/rectifier is at fault. Replace it and return to Phase A!
You have a reading of 1.5 V or higher on all three tests.
down arrow
 
 
Connect the BLACK multimeter lead to the RED output wire of the R/R. Connect the RED multimeter lead to one yellow wire. Check the reading. Repeat this procedure for the two other yellow wires.
Are any of the readings below 0.2v or above 1.00v on any of the three tests?
right arrow
Different Bad News! Regulator/rectifier is at fault. Replace it and return to Phase A!
You have a reading of around 0.50v on all three tests.
down arrow
 
 
Connect the BLACK multimeter lead to the negative output wire (BLACK/WHITE) of the R/R . If there is no output wire, connect the black multimeter lead to the R/R-case Connect the RED multimeter lead to one yellow wire. Check the reading. Repeat this procedure for the two other yellow wires.
Are any of the readings 1.00v or lower on any of the three tests?
right arrow
Different Bad News! Regulator/rectifier is at fault. Replace it and return to Phase A!
You have a reading of around 1.50v or higher on all three tests.
down arrow
 
 
Connect the RED multimeter lead to the negative output wire (BLACK/WHITE) of the R/R. If there is no output wire, connect the black multimeter lead to the R/R case Connect the BLACK multimeter lead to one yellow wire. Check the reading. Repeat this procedure for the two other yellow wires.
Are any of the readings below 0.2v or above 1.00v on any of the three tests?
right arrow
Different Bad News! Regulator/rectifier is at fault. Replace it and return to Phase A!
You have a reading of around 0.50v on all three tests.
down arrow
 
 
As this was the last test, the only thing that can be at fault is the battery itself. Replace it with a healthy, fully charged one and return to Phase A.
 
 


Next article: Stator Papers 5 - What about parts?