Dynamo issues

[AndyO]

My 54 G80S has the usual Lucas E3-N dynamo. Presently I can't get any output on my multimeter. I have tested as per Matchless workshop manual. Remove the 2 wires and connect them. With bike running put the +ve probe on any dynamo terminal and the -ve proble on an earth point. With the meter set to 0-20v no significant reading other than 0.4v
Before I remove the dynamo is there anything I can check? What's the most likely problem?
I'm new to dynamos so any advice appreciated.
Andy

[Iron Head]

I'm far from an expert Andy but, I believe, as long as the brushes and commutator are clean and making contact it can only be a fault in the armature or field coils. I did mine last year using the full kits of eBay and it was a really easy and enjoyable process. Take care with the Mazak end fitting which performs a lot structurally and is easily broken!

Iron Head

[Pharisee]

My 54 G80S has the usual Lucas E3-N dynamo. Presently I can't get any output on my multimeter. I have tested as per Matchless workshop manual. Remove the 2 wires and connect them. With bike running put the +ve probe on any dynamo terminal and the -ve proble on an earth point. With the meter set to 0-20v no significant reading other than 0.4v
Before I remove the dynamo is there anything I can check? What's the most likely problem?
I'm new to dynamos so any advice appreciated.
Andy

With respect, Andy, I don't think you have that quite right. You say "Remove the 2 wires and connect them.".... No. Remove the two wires from the dynamo and connect the two dynamo terminals together with a short length of wire. Unless somebody has changed it over, your bike would be positive ground so your multi-meter +ve probe should be connected to ground (earth) and the -ve probe should be connected to one of the two connected dynamo terminals.
John

[Harry44]

Hi, the next easy check is the field coil resistance. Multimeter on ohms measured from the terminal to earth.

You looking for about 3.2 Ohms.

Cheers Harry

[AndyO]

Thanks for that Pharisee John. The wording in the manual is confusing. I'll try again tomorrow as well as checking ohms output as suggested.
Andy

[SPRIDDLER]

I use a lamp instead of a meter. A lamp is a much better indicator of dynamo power output than a meter as even if you get a good voltage reading on the meter it won't indicate the dynamo's power under a load.
This is my test kit which I use for 6v and 12v systems. The 12v bulb should light brightly even on a 6v system since when doing the test the dynamo output is unregulated and will/should rapidly rise up to 20v with just 'normal starting off from a standstill' revs.
'D' and 'F' bridge the two 'sockets' at the end of the dynamo. 'Earth' goes to the frame or other clean metal part:

Dynamo test rig (640x480).jpg

Link (640x407).jpg

[56G80S]

Go on , Sprid, show them the spark test rig again!

Johnny B

[SPRIDDLER]

Go on , Sprid, show them the spark test rig again!

Johnny B

You're humouring me John

You must be referring to the 'Spridspark', my self-powered digital magneto tester with the audible current strength guide:

"Hmm" = No output.

"Ouch!" = Weak.

"Yeeeeow!" = Good. (The current kit is supplied with a strip of plasters for the head wound after contact with the handlebars).

CIMG0028 (640x480).jpg