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MG MG Y Type - Stopped charging, any ideas?

i got the YB out for a 2 hr cruise and it started raining on the way home. With wipers on I used the indicators and it blew a fuse. Fuel gauge, wipers & indicators stopped working. It was the outside fuse on the fuse box. Replaced the fuse and now all 3 items work again but the amp meter shows no charging. Testing the battery when motor running confirms its not charging.
I replaced the voltage regulator, didn't help.
Is there another fuse that I am missing?

How do I check if the generator is still charging and if it is where do you think I should look next?

Thanks in advance


K Weeds

Have you checked the output from the dynamo/generator? See https://www.mg-cars.org.uk/imgytr/umlvideos.shtml#Electrical

Is the fan belt tension correct?

Are the leads mounted securely?

Do you have continuity from the dynamo field coil through to the voltage regulator control box?

Is the voltage regulator control box working properly? See the same video section as above.

Are the contacts on your fuse box terminals clean?

Could be any of the above sir.

Paul
Paul Barrow

Thanks Paul.
I will have a go at checking the generator output as shown in video.
Of the 5 inlet posts on the regulator box shouldn't one be the generator output and therefore read higher than the batter output?

Thanks
K Weeds

Kevin,

You can find wiring diagrams in the Technical Center, then Technical Data then Wiring Diagrams and that will answer your question :)

Paul
Paul Barrow

Thanks Paul for your suggestions which I found very helpful.
I used the method of checking the generator while on the car plus the wiring diagram.
I checked each wire from the the generator (unplugged) to the regulator (unplugged) to confirm they were complete and not fused.
Then I checked the output of the generator when engine running and found no output so I removed the generator.
I drove to my closest vintage car club parts shed and bought a similar generator for $20 then took both to a auto electrician. Both these units failed on the test bed.
They had a brand new replacement which I purchased.
Once home I fitted the new unit and found no output at the generator. So the next day I drove back (2.5hrs each way) and they tested it, also found no output so they got another new unit out of the store. Fitted the pulley on this one but on the test bed found no output!
2 new units failed. After a couple of hours with 2 electricians scratching their head one unit worked. So I drove home and fitted it only to find no output again.
I gave up and switched to my 39 Dodge which has an issue with its regulator, I need to tap it lightly to get it charging and I'm sure a new one came with all its parts. While looking for it I found a used MG generator that came in the YB parts and fitted that. It works!
Now I had power to the wires at the regulator but still no charging so I swapped out several regulators and problem fixed.
The key to me sorting this failure was how to test the generator on the car and a wiring diagram to eliminate a break or blown fuse in the lead wires. Both of these I got from your links. Thanks so much for taking the time to offer help.
K Weeds

I wish I could find a testing method for the original Delco Remy 6v positive earth generator on my Dodge.
Next venture
K Weeds

Ken

Have you tried:

1) https://www.electricalrebuilders.org/eren/archive/ere_2005/ere_07_05_delco_gen_part2.pdf

2) https://www.gardentractortalk.com/threads/delco-remy-starter-generators-how-they-work-and-testing-information.93901/

3) https://www.delcoremy.com/getmedia/30ff0e99-7084-451b-8f2a-6745dd18a3b5/DelcoRemy_DiagnosticManual_web.pdf.aspx

4) https://www.jalopyjournal.com/forum/threads/delco-remy-generator-troubleshooting-help.269801/

or

5) https://www.delcoremyhistory.com/images/Training%20Manuals/Training%20Chart%20Generators%204.pdf

Just a couple of results from a quick google search.

Paul
Paul Barrow

Thanks Paul I'll read in detail.
In a quick read on one of those links it said Ford and Delco units polarize in a different manner and if you use the wrong method it wont charge. I'll see if I can find out the correct method.

Thanks
K Weeds

This thread was discussed between 04/04/2025 and 17/04/2025

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