Jump to content

GMC not charging

Recommended Posts

Check dynamo brushes, regardless of what volt meter is saying. Clean up commutator where brushes contact. When you say the battery lead off, are you reading at battery when connected, then taking the lead off? Because if your then not getting a voltage at the battery lead, the dynamo 'ain't putting out a voltage, your'e reading the battery. Two problems come to mind, brushes as said and polarisation. Have you been fiddiling latley? :nono: Before repolairising, disconnect regulator.

Deatils on the net. Loose fan belt, or slipping pulley, and of course CLEAN all contacts make sure there tight. Dynamos are pretty bomb proof, regulators can be a pain. Clean all the relay contacts gently with a emery board, don't be tempted to fiddle with adjustment, if any obvious scorch marks on winding, I'd advise a proffesional rebuild. Have you an amp meter fitted? If so what's that up to?

Link to comment
Share on other sites

Thanks Tony to try and add some more info, the amp meter dose nothing well not upwards anyway I'm sure it's working as shows a discharge. It had been converted at some time to 12v and has a Lucas small regulator on it. At the dynamo it's shows a fluctuating voltage from about 2v to around 6-7v when revving, it also shows shame at regulator input soon as u pull the bat lead off the output on the regulator drops to nothing and it dies



Link to comment
Share on other sites

I'd have the dynamo out, it should put out about 18 volts unregulated. Check it thouroughly, I know one that dropped a bearing and did similar. The bearing was dated 1945, so it couldn't be claimed under warranty. :-D Nothing on rebuilding a dynamo is very difficult, and it'll benefit from a good clean anyway. I've never had any trouble getting new bearings from local suppliers. Brushes and the holding springs are definitley suspect. You will have to repolarise the Dynamo afterwards. Do that before the regulator is wired up! Faliure to do so can be very expensive on regulators. To polarise you flick a lead from the battery to the feild winding, just once so you get a spark. Check on the web, for the life of me I can't remember which pole for which earth. An old Haynes manual has all the details, something like a Landy Series 1. If that dosen't cure the problem then you have a good clean working Dynamo anyway.

Note: Old Mechanic's tip: Before fitting run a file or emery over the end of new carbon brushes to make sure there is no insulating laquer left on.

Edited by Tony B
Link to comment
Share on other sites

This should look like your wiring:



If you want to troubleshoot the regulator I have a FREE Delco Remy manual for you!



Or it you like the TM version:



I recommend an ANALOG VOM because the digital may have trouble getting a good voltage from relays opening and closing.


Oh, and to polarize the generator:




The genny only puts out 8v at 1850RPM


If you are lucky all you may have to do it clean/file the relay points and then set the air gap, then set working voltages.


Its not hard... but will take a bit.


Basically I would look at the CUT-OUT relay first... that's the one that will signal if the genny should supply current. If that one is out of wack then your genny is physically isolated from the system.


Read the two TMs I listed... they should get you going.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...