Basic electrical help...please

M

MotoV

Hero member
Electrickery is my worst subject. I want to check the output of the alternator to . When I check at the battery I get less than one volt rise. 12 to 12.5 - I did charge the battery and its now at 13.2 V. I'm not sure what the output should be. I also want to get a feel for how the voltage regulator is working and what about the rectifier? Any simples checks I should do for each of these components to verify they are working?
This is for a 1979 1200, however, based on the engine number (5509), The engine is a 1977.
I read in another thread that the voltage coming off the alternator would be around 80VAC - would I check that at the rectifier?

Thanks
 
Quick check: place your meter across the battery terminals (engine off) should be around 12 to 12.5 VDC. Start the engine and rev to about 3000 RPM, voltage should go up to around 13.5 VDC.
Only a quick check, if any different further investigation required.

Terry
 
I found this really clearly written - but I'm no wizard - a review by a knowledgeable forum member would be good!

http://www.electrexworld.co.uk/pdfs/Troubleshooting-3P-PMG-&-RR.pdf

HTH.

H.

 
Great link..  My 3C (with a good battery) is about 12.2 V at idle, rising to a maximum of 12.65 volts at around 4300rpm.

It mostly stock with the exception of redone connections in the headlight and cleaned up internals on the switch gear.

thanks,
some call me Tim
 
That won't sustain the battery long term tim. Needs to be up close to 14 volts when revved. Although that depends on what you have switched on. So if you are only measuring that voltage when lights are off its not high enough. Either that or the battery in your multimeter is flat.
 
Update - I just finished the Install of a Redax-Sachse ignition-alternator and I don't have to worry about any stinkin' batteries...right?
The 1200 is now the hardest pulling Laverda I have ever ridden. The sachse replaced a DMC and seat of the pants says it is a huge improvement!...a few fuel bugs to clean up but I had several OMG moments on the first time out!
 
Drikko

coincidently it is a new battery in the multimeter.    Resting voltage (ie engine not running) is 12.65, and switching on the lights drops it to about 12.2.    I've put it on the charger for the night & will check again.

Cheers, Tim
 
I was mainly worried about the 12.65 volts at 4300 rpm, that's too low, should be into the 13.8 to 14.5 volt area well before those revs, especially if the lights are all off.
 
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