What's the proper procedure to test the AC output of the alternator on a '91 1000F? Can you unplug the alternator block connector while it's running to test AC output, or do you need to probe the connector from the backside while still connected?

I've already gotten good results on the alternator resistance tests (.4 ohms on all three yellow charge wires, 3ohms on Blk/White exciter coil circuit, and no shorts to ground). When I probed the back of the yellow AC charge lines from the block connector near the petcock while running I only see 1 or 2 volts AC each at 4krpm. I thought I would see 40~50 VAC.

Bike died in traffic again. I have a two month old AGM battery, and new (three months old) Electrosport ESR230 regulator. Problem I'm having right now is I see about 12.8V at idle, and max of 13.2V at 4k rpm. When cooling fan kicks on in the garage, despite 4krpm, voltage drops to 12.6~12.7V. Reason I want to check alternator is to determine if the unit is making enough source voltage.

Any help is appreciated!

 

Hi Brian - Great testing procedure you have taken.

Answer 1

"What's the proper procedure to test the AC output of the alternator on a '91 1000F? Can you unplug the alternator block connector while it's running to test AC output, or do you need to probe the connector from the backside while still connected?"

YES. and I concur that your resistance readings are correct in limits. If you don't see 40~50 VAC here then try following test.


Answer 2 - your next test...

Given that this bike uses an ELECTROMAGNET to provide the magnetic field (exciter coil circuit) the we must have battery voltage there to generate our output voltage. Therefor ...

1. meter on volts - neg to earth.
2. connect pos lead to BL wire on exciter coil circuit.
3. Turn on IGN SW (don't start) & you should see your FULL BATTERY VOLTAGE .. 12.??v approx on meter. (Too much loss of voltage here will give reduced output).
4. If no volts then check the 10A sub fuse. (This should not be an issue from what you have already stated).
5. If 12V is there then move meter pos lead to the W wire and confirm you still have the 12.??v.

This process confirms voltage at the exciter coil circuit, necessary to get your VAC output of about 45v.

REF:- Workshop Manual Page 14/2.

Hope this helps .... if you haven't done this test already.

 

Ok, here's my results:

Static battery voltage: 12.8v
Ignition ON battery voltage: 12.5V (headlights and taillight ON)
Voltage on black wire on alternator connector: 11.5V with key ON (black meter lead to - on batt)
Voltage of white wire on alternator connector: 4.5V (black meter lead to - on batt)
When bike running: 11.8V black wire, 4.8V on white wire

It seems I'm seeing a 1V drop from the battery to the exciter circuit on the alternator. I also checked the voltage at the headlight fuse socket, and also see 12.2v while key ON, bike not running, so this ~1V drop seems to be occurring across the entire system. When I pull all the fuses in the fuse box (no headlight or tail light) I see 12.8V at the fuse box, so I'm assuming the voltage drop is due to the parasitic draw of the headlight & taillight on the system.

The thing that really concerns me is I only see a max of 14.7VAC on any of the three alternator charge wires when probing the block connector while the bike is at 4kRPM.

Does this mean my alternator stator is bad? It's weird it passes the resistance tests, but clearly it's not making anywhere near 40~50VAC when revved up to 5KRPM.

 

Your certainly doing all the right tests.

I know you stated that you tested each of the yellow wires to ground (the metal part of the stator). But did you remember to test each of the yellow wires to each other (when they overheat they can short or leak to each other).

I agree you have a problem from your test results. If the above did not work then I suggest re-start methodical testing using the following.

http://www.electrosport.com/technica...ng-diagram.pdf

 

Thanks so much for posting that Naga. It looks like from that troubleshooting guide I need to wire up to temporary leads for + and (-) and put them to the black and white exciter coil contacts, then retest for 40~50VAC. If it's still not putting that out, then either my stator coil is bad, or the alternator shaft isn't turning to interrupt the field coil and create the AC on the charge coils. Is the alternator damper that so many I see have starting issues with a one-way clutch that spins the alternator shaft? If it was bad, would that also cause the hard/no start issues as well? I don't have any starter issues, as the bike spins easily on the button without delay.

 

>>>> i've never had this problem so don't want to comment. Seb to comment?

 

Well, the results are in on the alternator field coil test wired directly to the battery with 12.8v. 40VAC at 3Krpm. So, it's now clear the charging system in general on this bike is functioning perfectly, although not charging until 2kRPM doesn't help. It's still frustrating to know that if I get stuck in heavy summer traffic, I could end up with a stalled bike and another dead battery like I did about a month ago. Time to swap in my UK right grip switch cluster with on/off headlight switch. It may not be officially legal in Texas (DRL's are required), but I'd rather deal with a possible conversation with a police officer, than wait on a friend with a truck by the side of the road again!

 

As I read the thread, from the top you say that there is a drop when the fan kicks on. In traffic the fan will kick on and if it is causing a drain, kill the battery. You say it works but does it spin freely? If its dragging for some reason (dry bearings) it can cause a drain. Have you tried spinning it or checking the draw in amps when its running?

 

Tim, I haven't checked the fan for drag, but that should be easy. Thanks. I have a pretty good multimeter, but it's only got a 2A fuse for checking draw. I think the fan would kill my meter. I bet I could pull the thermoswitch ground wire, add the meter in-line, and check draw if I can pickup a more capable meter.

 

Hi Brian, I'm in Dallas as well. I'm in need of a stator for my '93. Any ideas where I can find one locally?