Author Topic: Charging issues  (Read 6949 times)

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Offline dankeller

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Charging issues
« on: September 13, 2016, 12:41:57 AM »
Hi. I'm having charging issues on my 1978 xs500e.

It's most noticeable with the headlight on. And I think it's most prominent when the bike is warm.

When I start in the morning at 2000 rpm, with no light on I can see 13.5 v, and it will climb to about 14.3v at 4000+ rpm.  With head light on its less, 12.6 at 2000 and will go to about 13.5 at 4000+.  Cold, the three stator wires show 0.7-0.8 ohms along the three pairs of connections.

15 to 20 minutes into my ride in stop and go traffic, I see the voltage drop to about 12.5v and continue down to 12.2v, averaging 3000rpm.  Hot, the three stator wires show 1.4, 1.4, and 1.1 ohms.

I'm not seeing continuity between the three stator wires and ground, but I checked after the bike cooled down a bit.

I have a new battery, and I replaced the regulator and rectifier with used ones.

Does the above mean anything to any of you?  Does it suggest my stator is at fault?

If so, stators from what year bikes will work in my system?  The Yamaha number for 1978 is different from the other years.

Thanks in advance.

Dan

When
« Last Edit: September 13, 2016, 12:49:14 AM by dankeller »

Offline guylr

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Re: Charging issues
« Reply #1 on: September 13, 2016, 03:09:10 PM »
Your cold readings on the stator wires are pretty good and the hot readings are not out of range. Try a few dynamic checks to see what is happening with the engine running. Test the input side of the system first. Field strength and regulator.
 
1. With the key on, check the Brown wire voltage at the regulator and field coil connectors. You should see within a few tenths of battery terminal voltage. Wiggle the key a little and turn the handlebars side to side to see if the reading changes. Crank the bike and check the reading at idle and revved up to see if it drops. If the reading was very low, say more than a volt or two below battery voltage then you may have corroded connector pins and or corroded mainswitch contacts. The brown wire current flowing through the field coil is what makes the magnetic field for the generator. Weak brown wire voltage = weak field strength = low output.

2. If your brown wire voltage checks out then perform this simple test of the regulator circuit. On this model the regulator controls generator output by varying the resistance on the green field coil wire to ground. Make a jumper wire to run from the green wire at the back side of the regulator connector to ground. Crank the engine and then touch the jumper to a good ground on the frame or engine. This bypasses the regulator and should make the generator go to full output. If you do this when the engine is hot and not charging well and the charge jumps up to normal then you either have a bad regulator ground or a bad regulator.

If the regulator bypass didn't change things then go on to test the output side of the system. Stator.

3. At the main multi connector probe between the three white stator wires with a voltmeter set to the AC scale of at least 20V. You'll have three combinations  A-B, A-C, B-C. With the connector unplugged (unloaded test) you should see 18-20 ACV at idle on the stator side. With the connector plugged (loaded test) in you'll see a drop in voltage to around 8-11 or so. The actual voltage is not so important so long as the three readings all drop and are close to equal when loaded. Try these checks on the cold engine when you seem to get OK charging and then when it's hot and not charging so well. If you see one or two of the voltage readings much lower on the hot test then your stator coils are shorting internally or to ground. If the stator pigtail wires are in good condition and not pinched at the case cover then your stator is bad. I believe that all TX/XS500 stators will work on your bike and that the change to the XS500E stator was "improved insulation" ;)

If one or more of your hot test readings is high, say above 13 volts or so, then your rectifier has one or more diodes going open and not loading the stator.

If I had to guess on one cause I'd bet on the bad rectifier ground.

Guy




« Last Edit: September 13, 2016, 04:17:47 PM by guylr »
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Offline dankeller

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Re: Charging issues
« Reply #2 on: September 13, 2016, 04:01:58 PM »
Many, many thanks Guy!  I'll go through your suggestions carefully in the next couple of days.

Dan

Offline dankeller

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Re: Charging issues
« Reply #3 on: September 15, 2016, 01:46:17 AM »
Hi Guy,

I tried some of your tests.

Test 1
When battery voltage is 12.37v across battery terminals (key on):
- field coil brown to battery negative is 11.15v
- regulator brown to battery negative is 11.3v

Test 2
Bike idling voltage 12.6v across battery terminals (headlight off) and jumpering green on regulator to ground (bike frame or negative battery terminal) does NOT change battery voltage.

Test 3
I didn't get to do this test today, but I did it a month ago when I suspected something was not right and I did get the readings you indicated on the three stator wires.

Additionally, resistance between top two field coil wires is 4.5 ohms (bike still warm) which I think is ok.
I do get 14.3 volts with light on when at 3-4000 rpm, but at idle with headlight on it gets to about 12.1-12.2v.

Does the above tell you anything?  Does it sound like a bad ground? If so, how do I track it down? Where and how should I look?

Many thanks.

Dan



Offline guylr

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Re: Charging issues
« Reply #4 on: September 15, 2016, 03:44:36 AM »
You tested the ground with the jumper test. It's OK. Your brown wire voltage is low and tells me the harness and switches need to have the connectors and contacts cleaned so that your voltage drop from the battery is less than 0.5V. Your revved charge voltage is good however.  At what rpm does the voltage rise to over 13? If it'starts at around 1600-1700 then your charging system is working normally and getting that brown wire voltage up should cure your problem . By the way what is your idle set at? Go for 1250-1300.

Guy
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Offline dankeller

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Re: Charging issues
« Reply #5 on: September 15, 2016, 05:39:58 PM »
Thanks Guy.  I've tried to keep the idle at 1200rpm.  It does change and I seem to be fiddling with the set screw every so often.  On that note, the bike seems to like 1400-1500rpm.  Is there any downside with leaving it at that?

Your comments are interesting.  I hope its just the brown wire contacts.  I'll go over those carefully in the next couple of days.  But you gave me an idea.  Can I try jumpering the brown wire at the regulator directly to the positive terminal on the battery and see if that makes things better?

I think at 2500-2700 rpm (can't remember exactly) the voltage rises over 13 with headlight on.  Also headlight on is key here.  There seems to be enough voltage with the headlight off.  But since I've been running with the headlight on I've noticed this charging issue.

Also when the voltage does rise, its slow, like 0.1-0.2 volt per second increase (is that normal?).

As always you are a ton of help.  Thanks very much Guy.

Offline guylr

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Re: Charging issues
« Reply #6 on: September 15, 2016, 08:46:38 PM »
1400 is a bit fast a can make for overheating if you idle for a long time in summertime but not too bad. Your idle instability may be due to a slight carb in balance and or governor springs get a little weak. Mine does it too.

Yes you can try a brown wire jump from the positive terminal to the brown wire at the field coil connector.

An easy check of the 13 volt rise is to watch the headlight and see at what rpm ithe suddenly gets brighter than when idleing.

Guy
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Offline dankeller

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Re: Charging issues
« Reply #7 on: September 20, 2016, 03:34:24 PM »
Hi Guy,

I did some more tests today.

With the bike started and warming up I get 14.3 volts (light off) and about 13.5 volts (light on) at 2000rpm. 

After 30 minutes of solid stop and go traffic (bike seems really hot) I'm seeing about 11.8 volts (light on) and 12.2 volts (light off) at idle, on battery. I can't remember the readings at 2000 but they were well below 13v.

Hot and loaded AC test all three about 9.5 v (ac), unloaded about 15.5 v (ac).

Do the low unloaded AC test readings confirm that the stator is the problem?

Also, with the bike hot at the end of the stop and go ride, the idle drops to 1000rpm and I need to turn in the set screw to get it back to 1200-1300.  (when colder, that setting gives me a 1500 rpm).

At the end of all this, battery is at 12.3 volts with key off.

Thanks.

Dan

Offline guylr

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Re: Charging issues
« Reply #8 on: September 20, 2016, 07:20:31 PM »
Re-do the stator tests with the battery fully charged to 12.7V or higher.
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Offline dankeller

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Re: Charging issues
« Reply #9 on: September 20, 2016, 11:40:51 PM »
Hi guy,

On the ride home today I was moving so could keep the revs up between 3-4000 and kept the headlight off. The battery was at 12.65 v when I parked.

The ac test loaded had all 3 connections at about 10.9.  The unloaded readings were all around 17.2. The resistance of all 3 was about 0.9 ohms. The field coil resistance was 5.5 ohms.
There is no continuity to ground between any of the stator wires or the two field wires.

Charging at 2000 rpm slowly climbed (.1 volts every 1 to 2 seconds) from 12.5 at idle to about 12.88.

All these readings are all over the place and don't mean anything to me. What I see is that when's the bike is warming up the charging system seems to be good, but when the engine gets hot the charging becomes very weak. With the headlight off and going at speed it is sufficient, but with headlight on and in stop and go conditions it is inadequate.

Thanks.

Dan

Offline guylr

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Re: Charging issues
« Reply #10 on: September 22, 2016, 02:50:47 PM »
It's perfectly normal for the system to discharge at idle. That's why the headlight will brighten when you come off idle. If you came in from the ride with the battery terminal voltage (key off) at 12.65V then I'm not seeing a problem. The unloaded/loaded stator checks are in the normal range. Your field coil resistance is a bit on the high side at 5.5. The spec is 4.04 +/- 10% but you aren't to far above that and it could be your meter.

Guy
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Offline dankeller

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Re: Charging issues
« Reply #11 on: October 01, 2016, 02:29:54 AM »
Thanks Guy.  The problem is that to keep the battery charged I have to have the headlight off and maintain a minimum of 4000 rpm.  The law here requires headlight on.  When the bike was warming up the voltage was good, but once at operating temperature the voltage at the battery was weak with head light on even at 4000 rpm (i.e < 13v).

So I got a NOS stator advertised for years 73-77 and installed it this evening.

I ran into a problem right away.  The stator i took out on my 78 has 4 wires.  3 wires to the 3 terminal plug and a lone wire that connects to a separate wire on the harness.

I haven't tried to run it yet.  In the meantime, can someone tell me if I need to do anything with that lone wire to make the thing work?

The 78 wire diagram shows the wire going to a relay.  The 500c schematic doesn't have this relay.  How is the relay supposed to work?  It looks like it is connected to the tail light, the stator, the kill switch, and the headlight switch.  Maybe the fault was with this relay all along.  How do you test it?

Many thanks in advance.

Dan

Offline guylr

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Re: Charging issues
« Reply #12 on: October 01, 2016, 03:52:52 AM »
I believe the extra wire is the tap for the headlights on relay not used on the older models. I don't have a '78 wiring diagram handy so I can' see how your bike is equipped. If your bike doesn't have the headlight on/off switch on handlebar switch then you'll need to either make a new stator tap or back date the bike to a '76-'77 handlebar switch. The tap in most diagrams is shown as coming from the point where the three coil windings are connected to each other. Some of those tap wires also have a diode in line to create DC output that will trip the primary side of the headlight on relay. Check that wire on your old stator to see if it's there or maybe in the harness or part of the relay.

Guy
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Offline dankeller

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Re: Charging issues
« Reply #13 on: October 01, 2016, 05:27:30 AM »
Hi guy.  Here is the wiring diagram. Does it tell you what effect the missing stator wire will have on the relay and anything else?

Thanks

Dan

Offline guylr

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Re: Charging issues
« Reply #14 on: October 01, 2016, 02:57:02 PM »
You're in luck. I should have remembered you said that you could turn your lights off. The 1978 models were a transition year for Yamaha where it went from all manual light control in 1977 to all automatic control in 1979. The 78's still had the headlight on/off switch so you could turn the lights off. I believe that your system will work fine without the relay but you will need to remember to turn your lights on with the switch. If they weren't coming on before then either that tap was broken or the relay was bad. Just remove the relay.

For 1979 on US and probably your Canadian models, the light would come on when you started cranking the starter and the stator began making current. The relay had a loop circuit in it that would keep the lights on if the engine didn't start or if you stalled it. But there was no switch on the handlebar.

Guy 

P.S. Let me know if that works. The wiring diagram is a bit fuzzy but I think I read it right.
« Last Edit: October 01, 2016, 03:12:30 PM by guylr »
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