Author Topic: How much to rebuild a generator? (Read 178 times)

FordDude · « **on:** March, 19, 2010, 01:55:01 PM »

My Dad's convertible needs the generator rebuilt. He says the dude wants 100 bucks to do it, and that is bringing the generator to him. I am going to have to go to Dad's house and remove it as he is unable to do it now. The problem is the rear bearing in the generator, it is making noise. Fair price or any suggestions. fd

AzPete · « **Reply #1 on:** March, 19, 2010, 01:58:37 PM »

Not sure but how much to buy a new/rebuilt one? Also, can you do the rebuild yourself. I did them years ago and it was pretty simple, especially bearing replacement.

Found this...the bearings are real straight forward.

The armature should be tested on what is called a "growler" first. This will determine if any of the winding is shorted out. If it is shorted out, then the armature will need to be re-wound. The next test is a 'bar to bar' check with an ohmmeter. This is a check for shorts between the commutator bars. If this also checks out OK, then the commutator can be turned. This is done in a lathe. The mica between the bars should also be undercut the same depth as the width of the mica. The mica is also removed from the sides of the bars in the undercut slots. The edges of the bars are then chamfered slightly and the commutator is then burnished. For small automotive size armatures, balancing is not usually required. For larger diameter armatures, dynamic balancing should be performed.

Bearings should be replaced and new brushes installed. The brushes should also be 'seated' to conform to the diameter of the commutator. This is done by placing sandpaper around the diameter of the commutator (one layer with no overlap) while it is installed in the generator housing. Then the brushes are installed and the armature is spun by hand a few revolutions. This will sand the face of the brushes to conform to the diameter of the commutator. The sandpaper is then removed. The generator can then be installed.

All of the above is also correct for any electric motor that has a commutator.

Undercutting is NOT done on starter motor armatures. That is because the brushes used in starter motors have a high copper content rather than just carbon due to the high current draw and thus negating the need for undercutting.

NOTE:

It is VERY important to polarize the generator before starting the engine after the generator has been worked on. Even if just the brushes have been swapped out. If this is not done, the armature and/or the regulator can burn up.

Midlife · « **Reply #2 on:** March, 19, 2010, 02:45:47 PM »

Dang, Pete...you even lost me on your explanations!

To answer the OP's question, $100 is not unreasonable. That's about 2 hours worth of work. $60 would be better, but with inflation?

AzPete · « **Reply #3 on:** March, 19, 2010, 03:03:50 PM »

Quote from: Midlife on March, 19, 2010, 02:45:47 PM

Dang, Pete...you even lost me on your explanations!

....that was the short version. I used to rebuild them all with a drill press and hand tools. The armature test was usually just if it worked before, then it is good.