Topic: Voltage regulator drawing to many amps???

[Lamp]

I keep blowing the main (and only) fuse on my 72 cb750. I can go ride for about 15-30 min then it just blows. I've noticed my turn signals don't blink as fast or bright as they should either. Anyways when I unplugged the black wire from the voltage regulator, the main fuse cooled off, and my turn signals got brighter and started blinking correctly. Anyone else had a voltage regulator do this to them?

[dave500]

it might have an internal short?the reg dosent pull much current,,the field might have a shorted?i rarely post in electrical threads ,i need to see them first hand.

[Spanner 1]

I'm presuming your referring to the stock regulator in your question...the regulator is not the problem in this case, but a combination of 40 yr. old wiring connections thru' the bike and the fuse holder being corroded. A coating on the fuse clips will cause a high resistance and allow the fuse to heat with normal current ( amps ) draw of the bike ! The fuse clips can 'look' clean but not pass the required power.
In other words, bite the bullet and undo and shine all the connectors on the bike....... takes an hour or two, but makes you good for years ! Don't forget the main battery ground terminal. File the frame for shiny metal and file the ring term. too... Shiny is the key word, don't settle for less,
When the fuse clips are all cleaned-up, carefully bend the clips inward so as the clip has a tight grip on the fuse. Also, look at the back of the fuseholder for burning....... I think you get the idea  ....

[bollingball]

If it does not have to be 100% correct put a new style in line fuse in but still clean all the other connections.

Ken

[Bodi]

The regulator itself doesn't draw much power at all but it switches the power to the alternator field coil - that pulls 3 or 4 amps when on. I agree that your problem is likely from corroded electrical connectors (bullets) and fuseholder clips. If the clips have gotten really hot they lose their springiness, plus the soldered connections in back may have melted and the connections there are now loose. If so, putting in new inline fuseholders with modern bipin fuses is a good option. far from "stock" but more reliable.
The original fuses themselves are an oddball size. American fuses almost fit but not properly. The contact area is reduced if you install them, that adds to the heating.

[scottly]

The regulator itself doesn't draw much power at all but it switches the power to the alternator field coil - that pulls 3 or 4 amps when on.

The field only draws a max current of about 2 amps; the stock regulator itself draws about 1/3 amps.

[Spanner 1]

7.2 ohms for the field coil @ say, max. 14.5 v in the system = about 2 amps. But allow for 40 yrs. old and 'hardening' of copper conductors, oxidation of connectors and the effect of thousands of heat/cool cycles on the components = 3 amps believable IMO.

[Lamp]

My turn signals started behaving normally, and the fuse cooled off when I pulled the black wire off the regulator. I know I may have other problems but why this make such a difference?

[Spanner 1]

See replies above..... or do whatever  ... with the black wire pulled = working off the battery only= no charging. Leave your turn signals on and see how long they will continue to flash .... less than 1 minute I would guess before no more flash ( normal with no charging from the alternator, black wire pulled )....