alternator troubleshooting: the answer

[jpnovak]

I noticed the alternator had no output when I was setting carbs the other day. For those who have followed my project I solved the high idle problem which then prevented me from setting the timing. Both were caused by a carb butterfly valve that was slightly crooked when I disassembled and rebuilt the carbs. I won't make that mistake again.

The other night I pulled the alt to start trouble shooting. I checked all of the bench tests.

These tests include measureing diodes between
D-/D61, diodes between D+/D61
and the individual diodes to the respective posts.

Each test failed when I would get to D61 contacts. i assumed I had some bad diodes. The only way to tell is to take it apart.

The next step was to split the alternator. I bumped the housing with a rubber mallet which then allowed me to rotate the housing slightly. Then I reversed the long screws and used them against the front housing to press out the front cap and rotor. The stator then came out by removing the nuts securing the binding posts.

I then proceded to recheck all the individual diodes. They all test fine. HMM why would the test fail to the binding post and not on the inside. Must be a contact issue. Sure enough!

The shop the rebuilt the alt a year ago neglected to clean the D61 wire and post. It was dirty and crusty. A little cleanup with emory cloth and a fine file and then reassembly.

The good news is that I have a working alternator once again. Teh bad news is that I am more skeptical of the abilities of an outside shop to complete any thorough work.

Sorry for rambling. I just had to vent.

[RickM]

This confirms what some have said in the past.

Even many Bosch "factory" rebuilt units come back poorly done.

[Crachian]

Jamie, who rebuilt it?

I just replaced mine ('73 targa) and haven't buttoned it back up yet.

[jpnovak]

It was rebuilt in NC over a year ago prior to my move to TX. I had used this shop several times before with good results. I never noticed the problem since the engine has only been working a few weeks.

you may want to do the bench tests to confirm yours is good before bolting it in place. Its easier than pulling it back out. I am sure it will probably be fine.

I see your are local. You will have to start coming out on our fun runs.