Question-------------------------
Followup To
Question -
-------------------------
Followup To
Question -
I have a 1999 Honda 750 Magna with 17k miles. Never had any problems. About three weeks ago while riding after dark I noticed the headlight would get dim as I start off from a full stop. Not so dim where I could not see but not bright. As I would pull the cluch in to stop the light got brighter (as bright as it always has,not over bright like system is overcharging). This went on like this for about 10 miles then the headlight would stay bright all the time. Then after about 15 more miles it would get dim as I start off and ride and brighter when I would stop.
I installed a new battery and cleaned connector to regulatir/rectifier. Still same problem. Put a volt meter on battery. With bike cold,started up fine. Charging to 14.8v. But when I run the rpms up to 3000 charging went down to around 14.2v and headlight got dim. After running for 5 min charging went down to 12.8v and would stay there even when I ran the rpms up but now the headlight was bright and would stay that way. The three yellow wires from the alternator were very hot where they connect into the connector for the regulator/rectifier but did not show any sign of overheating.
To check the regulator/rectifier the service manual states to use certain meters or you will not get a true reading. I do not have their brand so used the one I had. Checked the three yellow wires to the two green wires. Got a reading per the book. Checked the three yellow wires to the two red/white wires and got no reading at all. Meter showed OL an all settings for resistance.
The old battery was fully charged and never failed to start the bike so the charging system has been working. Even after running it for two hours yesterday it fired right up today.
Answer -
Hi Tim,
Visit the following website and check out their troubleshooting chart:
"www.electrexusa.com"
Check the output of each leg of the altenator's Y-winding as described in the chart. Also do the same per the service manual's procedures.
Measure voltage of the headlight.
Measure the lighting coil's resistance.
Measure resistance of the headlight resistor.
You've already tested the Regulator/Rectifier.
You should find the source of the problem with the above listed tests.
Respectfuilly,
Mark Shively
Thanks for the info Mark. All these checked good. Also,good sready voltage from alternator. When I disconnected wires from alternator at regulator/rectifier and ran rpms up light never went dim. When I disconnected wires from regulator/rectifier that go to battery lights never went dim. My BIGGEST concern is the wires (three yellow wires) from alternator that plug into connector going to regulator/rectifier are getting HOT. Should these wires be getting hot?
Thanks again,
Tim
Answer -
Tim,
The yellow wires do get warm though their insulation should not discolor or become deformed.
The altenator produces an abundant supply of charging current. The regulator/rectifier disposes of excess current by shunting it to ground. The result is heat. Heat radiates thru the reg/rec's heat sink and to wires.
Also, corrosion and poor connections may cause excessive resistance within the yellow wires. The result could be similar.
If there's evidence of heat damage to the yellow wire's insulation or multi-connector, there's a problem with the reg/rec or other component in the circuit.
Applying dielectric grease to the multi-connector may help prevent cossosion and water shorting.
It may become necessary to replace the multi-connector if it is not clean and tightly connected. The terminals should appear shiny for best results. Terminals appear dull with time, and in some cases corrosion forms.
Honda had a problem with this same connector on their 1985-86 models. The connector would melt. Part of the fix was to eliminate the connector by soldering the yellow wires directly. Honmda eventually remanufactured the alternator with heavier gauge wiring and heavy-duty multi-connector.
Mark
Hi Mark
With all the troubleshooting I have done would you sat the regulator/rectifier may by going bad or have I missed something?
AnswerThere's a problem with the charging system. Likely the lighting coil or the regulator.
Without being present and performing electrical diagnosis personnaly, I am reluctant to 'guess' the exact cause.
Avoid replaing parts in hopes of fixing the problem.
I suspect the reg/rec is failing when rpm's are above idle.
Which Service Manual are you using?
Send me your email address. I'll return Honda tech information in email attachments. The information is more in depth than the medel specific manual.
Mark
