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Superboar

Does the RR work on the AC circuit?

9 posts in this topic

'Lots of discussion about blown headlights. My '03 WR450 is showing 22 volts AC at the headlight but 14.5 volts DC at the battery when the engine is reved. So the rectifier/regulator (RR) is working for the DC side. There is a wire spliced into AC headlight circuit that runs to the RR - electrically the RR is not BETWEEN the headlight and AC circuit. So, does this wire to the RR suck over voltage out of the AC circuit? Or not which blows out the bulb...

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Not sure about your question, but FYI there were a lot of probs with the 03-04 regulators, mine over voltaged the CDI and cooked it and that was not a cheap replacement. $450 plus for the new CDI and regulator. I heard there was a Yamaha tech bulletin out about the regulator problem for the 03 and 04.

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Not sure about your question, but FYI there were a lot of probs with the 03-04 regulators, mine over voltaged the CDI and cooked it and that was not a cheap replacement. $450 plus for the new CDI and regulator. I heard there was a Yamaha tech bulletin out about the regulator problem for the 03 and 04.

Really????? Never heard that one before. I've put over 10,000 miles on both my '03 & '04 WR's and never a hint of a problem. If it was a big problem you would think there would be a lot of threads here on TT about it. That aside to answer the OP's question yes the rectifier/regulator also regulates the AC circuit.

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Maybe it wasn`t a huge problem but it doesn`t cost anything to check your voltage, as opposed to just assuming things are OK.

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...yes the rectifier/regulator also regulates the AC circuit.

DC circuit

coil---RR----battery and other DC components

AC circuit

coil

|

|-------------RR

|

headlight/taillight

How does it do this if the RR is in parallel with the AC circuit?

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DC circuit

coil---RR----battery and other DC components

AC circuit

coil

|

|-------------RR

|

headlight/taillight

How does it do this if the RR is in parallel with the AC circuit?

It's what is called a shunt regulator. It pulls the excess voltage (well current actually) to ground. Almost all dirt bikes use this type of regulator on the AC circuit. Not particularly efficient but it works.

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Shunt regulator....

OK, I see in the electrical specifications that it lists both DC regulator (14.1-14.9 V) and an AC regulator (13.0-14.0V). My voltage at the headlight is 22 VAC. So it's going to need a new regulator.

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Superboar:

Start the bike and rev it. Voltage at yellow wire should be 13.0 to 14.0 volts (set your multimeter to ACV-20). If out of spec, it's the rectifier/regulator.

One thing I learned today is that cheap multimeters are not accurate on resistance measurements. I borrowed a good one from a friend and rechecked the coil resitance. It was within spec. My meter was way off.

Same goes for AC voltage check. You need to have an ACV-20 setting on your tester. Lowest mine had was ACV-200 and the reading was off by 1.5 V (too low).

Edited by Navaho6

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Shunt regulator....

OK, I see in the electrical specifications that it lists both DC regulator (14.1-14.9 V) and an AC regulator (13.0-14.0V). My voltage at the headlight is 22 VAC. So it's going to need a new regulator.

Yep. It's a combined unit (AC & DC).

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