2001 HONDA CIVIC ALTERNATOR OR SOMETHING ELSE ??

  • Tiny
  • vitual
  • 2001 Honda Civic

Electrical problem
2001 Honda Civic 4 cyl Two Wheel Drive Automatic 137000 miles

Ok, this may sound stupid, but I did it to myself.
car - 2001 honda civic Lx 1.7
this saturday morning, I was trying to investigate a strange rattling sound, coming from left side of engine while cold and disappearing after 15min driving. I was'nt sure if it is from ac or alt pulley or from timing belt area. So I took apart alt belt, started the car. Car started fine, sound was still coming from timing belt cover area, so I found out the source of sound. NOW I put the belt back, tightened it and started the car, car again started fine, ran for 2 seconds, then RPMs dropped and came back, then I noticed that battery light was on, on dash board. I knew something wrong with with battery or alternator. I took it to autozone, they checked battery said it was bad. I got a new battery and came back. I replaced the battery but light was still on. I checked new battery voltage it was 12.6, I started the car, voltage went upto 14.4 or 14.5, then turned on headlights, rear defogger, blower, tape one by one. Voltage at bat terminals went down to 12.8, 12.9. I asked someone to rev up the car to 2000 RPMs, voltage came back to 14.2.
then I disconnected the battery while car running, engine went on running, no stopping or stalling.
Finally I checked under hood fuse #9 and under dash 10 & 4. All were ok.
Car now starts and runs fine, with everything working but battery light is on on dashboard. Any suggestion what might be going on.

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Sunday, October 24th, 2010 AT 9:02 PM

5 Replies

  • Tiny
  • rasmataz
  • Member

Sounds like the computer controlled of the field generation circuit of the alternator is malfunctioning-Get it cheked

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Sunday, October 24th, 2010 AT 10:23 PM
  • Tiny
  • vitual
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What is "computer controlled of the field generation circuit of the alternator"?

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Monday, October 25th, 2010 AT 2:55 AM
  • Tiny
  • rasmataz
  • Member

It is some sort of a built in voltage regulator in the computer by using resistances to control the alternator output

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Monday, October 25th, 2010 AT 4:51 AM
  • Tiny
  • vitual
  • Member

Thanks, is it the built-in voltage regulator in alternator, or a separate one in ecm/pcm. One Honda manual also says to check multiplex control system for stored DTCs if there is battery light staying on?
By searching over internet found that usually battery terminals have high (>15 volts) voltage when voltage regulator is bad . Do you think it is voltage regulator because voltage falls down to 12.9 at idle with all accessories on? Or voltage does not necessarily needs to be >14.5 for voltage regulator to be bad?

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Monday, October 25th, 2010 AT 5:34 AM
  • Tiny
  • rasmataz
  • Member

When the electrical system is fully loaded-the battery voltage should be 13.5-14.5 volts engine idling. The regulator is built into the computer-double check the drive belt tension and the wiring connectors on the computer

If the voltage is below 13 and over 16 volts the voltage regulator is not doing its job.

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Monday, October 25th, 2010 AT 5:49 AM

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