Logo
FULL SITE MENU

Question on rectifiers

fastjeff

fastjeff

Gold Medal Contributor
I know about the theory of dio

I know about the theory of diodes and how rectifiers work. What I don't know is what my volt meter should read as the motor is idling: I get a series of spike of 18 volts registering on the 20 volts DC scale.

Is this normal?

Jeff
 
"One more thing: Is there a s

"One more thing: Is there a simple test I can use to determine if the rectifier is a good, like trying to run a 12 volt light bulb circuit through it?

Thanks,

Jeff"
 
1. To test half of the rectifi

1. To test half of the rectifier:

* Obtain an ohmmeter.

* Connect the red test lead to the alternator terminal.

* Connect the black test lead to the positive terminal of the rectifier.

* The ohmmeter should indicate continuity.

* Reverse the test lead connections. The ohmmeter should indicate NO continuity. Half of the rectifier has now been successfully tested.

* Repeat the test for the other half of the rectifier.

2. To test the Diodes:

* Connect the red ohmmeter test lead to the alternator terminal.

* Connect the black test lead to the rectifier ground stud.

* The ohmmeter should indicate NO continuity.

* Reverse the test lead connections.

* The ohmmeter should indicate continuity. Half of the rectifier has now been successfully tested.

* Repeat the procedure to test the diodes for the other rectifier half.

* Replace the rectifier if the unit fails any part of the foregoing tests.
 
"Jeff the voltage spikes don&#

"Jeff the voltage spikes don't sound normal, however, will admit that I have never really took a good look at the output from the rectifier directly just to see what it's doing.

Trying to rig up a light would probably simply result in a blown bulb. It's a rectifier, not a regulator, so it really needs the battery to act as the regulator and capacitor for the voltages it's throwing out and assumed that the battery is doing what it's supposed to - taking care of the wild/fluctuating output from the rectifier.

I have always tested the voltage at the battery, looking for 13-14 volts across the two (battery) terminals while the motor is running."
 
"..."I have always tested

"..."I have always tested the voltage at the battery, looking for 13-14 volts across the two (battery) terminals while the motor is running."

Me too, and I get that wild 18 volt intermittent spikes! The battery IS staying up, so...

Noel: Thanks for the procedure. It's going in my Merc file.

Jeff"
 
"Jeff, do you have access to a

"Jeff, do you have access to a DVA tester? might want to check out the charge coils on your stator - see if they have gone wild. You don't need them to cook and take out everything."
 
Graham:

Ran the beast yeste

Graham:

Ran the beast yesterday in a barrel and it APPEARS to be charging. I'll try it on the boat and find out for certain.

Thanks for your inputs!

Jeff
 
"Hi Jeff i have found the volt

"Hi Jeff i have found the voltage go up and down on unregulated charging systems too,with out a rectifyier you could run a 12volt 50watt spotlight and it would be dull flickering at idle and as the revs go up so did the intensity."
 
"Thanks, Jamie. THe fool thin

"Thanks, Jamie. THe fool thing must keep the battery charged or Carl's customers would have been raising hell.

Jeff"
 
"Guilty as charged! My photo&

"Guilty as charged! My photo's been on the wall in Post Offices too, I'm told.

Jeff"
 
"Ya, and that's his "b

"Ya, and that's his "big water" boat, wait 'till he posts a pic of his "puddle hopper"
"
 
Back
Top