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generator light
71dub - November 20th, 2015 at 05:57 PM

Hi guys i have a 1971 super bug and when increasing engine revs the generation light comes on .when at idle light goes out.have replaced battery and replaced generator brushes .A thoughts would be appreciated.Thought may be earth problem .

ragged - November 20th, 2015 at 07:27 PM

Voltage regulator. It's under the back seat.

AA003 - November 21st, 2015 at 11:32 AM

Could be a few things but you need to check everything wirh a voltmeter first before you waste time/money.

psimitar - November 21st, 2015 at 11:15 PM

Yea could be be as simple as a loose connection or bad earth so if you have a voltmeter then check online for how to do a voltage drop check on the charging circuit wires and also take a look at Speedy Jims website from USA. He has lots of useful electrical diagnostics for you to follow and will also tell you how to check the alternator/genny is working properly.

No point spending on a new regulator unless you really have to cos the quality of them is crap especially for the price you pay for them these days.

71dub - November 23rd, 2015 at 04:57 PM

Hi guys well sent some time at weekend and replaced worn generator brushes ensured battery fully charged checked operation of generator and is charging correctly .checked voltage regulator and is charging correctly .cleaned battery earth at body and at battery cleaned earth at gearbox to mount under the car .But am still having the generator light come on when engine revs increase.Thoughts

psimitar - November 23rd, 2015 at 06:11 PM

Did you check the voltage to the battery as you revved the engine?

12.2-12.6V is normal for engine off and 13.8-14.6V is good for the engine running. Being a genny it will probably be at the lower end at idle as they don't produces peak voltage until somewhere between 1500-2500 rpm. Can't remember exactly but if you see the voltage at the battery drop back down to what it is with the engine off then it's either the regulator or possibly the windings in the genny breaking down.

Speedy Jim has a tutorial for checking the genny when not connected to the regulator and if that checks out then regulator is the only option.

AA003 - November 24th, 2015 at 05:51 AM

It could also be a faulty ignition switch or ignition circuit.

southspark - November 24th, 2015 at 07:12 AM

The generator light has two supplies, one from the generator the other side of the light gets an ignition supply via the ignition key and a fuse .Check your ign. fuses either for blown or corrosion.
regards Paul

71dub - November 24th, 2015 at 05:20 PM

Thanks guys am slowly working through the suggestions before parting with hard earned cash will keep you up to date

psimitar - November 25th, 2015 at 04:41 PM

IIRC the ignition supplies 12v to all 3 of the dash lights. Oil, Genny and indicator. Each bulb then has a switched ground to make it light up. In the case of the oil it's the sender unit and oil pressure breaks the switches contact to earth.

For the genny the regulator earths the dash bulb until voltage is produced by the genny which then breaks earth contact and is also trying to feed 12v to the dash bulb. As there is no earth anymore then the light cannot light up :)

So long story short I think it unlikely to be an ignition switch problem. Not that it couldn't be but pretty unlikely.

71dub - November 28th, 2015 at 09:26 AM

ok guys up date generator brushes not bedded in .took to auto electrician to get checked generator light didnt come on at all .charge rate checked and regulator checked all ok .All put down to not cleaning commutator before installing new brushes .All fine now

psimitar - November 28th, 2015 at 06:35 PM

Ah padowan. Lesson learnt. Always a good idea to clean the commutator of any motor when replacing the brushes and I have socket attachments for my drill so I can spin up the motor/genny to help bed the new brushes in :)