Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

Rebuilding an alternator?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Danno, Oct 24, 2001.

  1. Danno

    Danno 1/2 ton status

    Joined:
    Aug 4, 2001
    Posts:
    487
    Likes Received:
    0
    Location:
    Rockford, IL
    My alternator is slowly dying on me... I can watch the voltage drop as I turn on headlights, heater and radio.

    I've never rebuilt an alternator, and I was wondering how hard it is to do?

    Also, anyone have any rebuild kits they can recommend? I was just going to go to NAPA and see what they had.

    Thanks!

    1984 K5 Blazer 4x4 Silverado
    6.2L diesel, 700R4, 3.42 gears, 31x10.5" tires
     
  2. Alex

    Alex Registered Member

    Joined:
    Jun 19, 2001
    Posts:
    78
    Likes Received:
    0
    Location:
    Northern California
    Danno, the least expensive rebuilt is to replace the brushes (Napa sells a kit for approximately $10 depending on the alternator) and clean the copper coil with some type of emery-cloth. Once you remove the case you’ll be able to access the brushes and coil. You may also have to replace the regulator depending on its condition. If all else fails, then just go to any parts house that sell the lifetime warranty alternator. They’re worth the price if you have any problems with them.
     
  3. '73 K5

    '73 K5 1/2 ton status

    Joined:
    Feb 17, 2000
    Posts:
    1,763
    Likes Received:
    0
    Location:
    Kansas
    Reman. alternators are pretty cheap. I always just bought one of those when I was having trouble...until recently I had the cash to get a Powermaster 140.

    '73 K5
    Chevy good...Ford bad
     
  4. Danno

    Danno 1/2 ton status

    Joined:
    Aug 4, 2001
    Posts:
    487
    Likes Received:
    0
    Location:
    Rockford, IL
    I'd go get one, but I'm kinda interested in seeing how hard this is.

    I used to be really good at electronics and what not. I'm starting to get interested in this stuff again.

    If the one that's on the truck right now has a lifetime warrantee, I'll probably just replace it. If not, I'm gonna rebuild it. :-)

    1984 K5 Blazer 4x4 Silverado
    6.2L diesel, 700R4, 3.42 gears, 31x10.5" tires
     
  5. Danno

    Danno 1/2 ton status

    Joined:
    Aug 4, 2001
    Posts:
    487
    Likes Received:
    0
    Location:
    Rockford, IL
    I'm thinking it's the brushes. I had similar symptoms when the alternator went out on my old Oldsmobile.

    Cool... Thanks for the tips/suggestions!



    1984 K5 Blazer 4x4 Silverado
    6.2L diesel, 700R4, 3.42 gears, 31x10.5" tires
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,982
    Likes Received:
    191
    Location:
    Roy WA
    You checked voltage while its running with a voltmeter? (not stock one of course) My truck also likes to dip in the 12's when the lights are on, and the heater is going, but it's because my idle is too low..650 or so. Keep forgetting to turn it up a bit. Just needs another 100RPM or so and it jumps to 13+ with the same load.

    Rebuilding them is easy. You can replace even the bearings with just a good socket set. No wiring necessary, all unbolt and replace/reconnect in reverse order. Paperclips are your friend to hold the brushes in place. : )

    Let me know how much a rebuild kit costs now...I just took mine apart like you are thinking, partly to see how they are inside. One thing I absolutely hate about remanned alternators is that at least half teh time, the amp rating is ground off the case.

    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>www.dorianyeager.com/index2.html</a>
    Why insist on counting when the ring gear has the tooth counts stamped in?
     
  7. HarryH3

    HarryH3 1 ton status Author

    Joined:
    May 31, 2000
    Posts:
    10,384
    Likes Received:
    2
    Location:
    Georgetown, TX
    Check out these guys: <a target="_blank" href=http://www.alternatorparts.com/index.html>http://www.alternatorparts.com/index.html</a> They have all the goodies you need to rebuild or even hop up you alternator for higher output. [​IMG] Summit Racing also sells the Iceberg upgrade kits.

    <font color=black>HarryH3 - '75 K5</font color=black>
    <a target="_blank" href=http://www.angelfire.com/super/ThunderTruck>www.angelfire.com/super/ThunderTruck</a>
    It's a great day to be alive...
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,982
    Likes Received:
    191
    Location:
    Roy WA
    Cool site. Maybe if I look around long enough, I'll find something to boost low RPM output! : )



    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>www.dorianyeager.com/index2.html</a>
    Why insist on counting when the ring gear has the tooth counts stamped in?
     
  9. HarryH3

    HarryH3 1 ton status Author

    Joined:
    May 31, 2000
    Posts:
    10,384
    Likes Received:
    2
    Location:
    Georgetown, TX
    Some of those mega output alternators still put out a pretty healthy current at low RPM's. [​IMG] Some of the companies claim they can crank out 65 amps with the engine at idle. [​IMG]

    <font color=black>HarryH3 - '75 K5</font color=black>
    <a target="_blank" href=http://www.angelfire.com/super/ThunderTruck>www.angelfire.com/super/ThunderTruck</a>
    It's a great day to be alive...
     
  10. 79k20

    79k20 1/2 ton status

    Joined:
    Oct 15, 2001
    Posts:
    144
    Likes Received:
    0
    Location:
    s.e. kansas
    it is very, very easy to rebuild one. i used to work at a place that built alternators, also my mom is the buyer/planner at the same place and she showed me how to rebuild one. check the brushes thats usually the problem.

    sean

    79 k20(duh) d44, 14bolt, built 350,350,np203,9"lift
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,982
    Likes Received:
    191
    Location:
    Roy WA
    I don't know enough about electronics to know why I can't get decent low RPM voltage out of any of MY alternators, but I was hoping to use a stock good one I have, and somehow boost low RPM voltage...oh well : )

    65 amps at idle is fine, but I sure wish you didn't need a 140amp alternator (with the matching price tag) to get there!

    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>www.dorianyeager.com/index2.html</a>
    Why insist on counting when the ring gear has the tooth counts stamped in?
     
  12. HarryH3

    HarryH3 1 ton status Author

    Joined:
    May 31, 2000
    Posts:
    10,384
    Likes Received:
    2
    Location:
    Georgetown, TX
    An alternator generates more current as RPM's increase. At low RPM it can only put out so many amps. Resistance (the load), voltage (the pressure) and current (the volume) all directly affect each other. Do a search on the internet about Ohm's Law if you want to know all the nuances. It details the relationship between the 3.

    Basically, Volts = Current * Resistance. So as resistance drops, current must increase to maintain the same voltage. As you turn on more items (lights, wipers, etc), the resistance seen by the battery and alternator drops. A given alternator can only put out a fixed amount of current at a given RPM. Once you exceed it's capacity to create current , then output voltage will begin to drop (because the resistance of the load hasn't changed). Unfortunately, the only solution is to increase the abilty of the alternator to produce current. This is directly affected by the size and number of windings, which is directly proportional to cost. [​IMG]


    <font color=black>HarryH3 - '75 K5</font color=black>
    <a target="_blank" href=http://www.angelfire.com/super/ThunderTruck>www.angelfire.com/super/ThunderTruck</a>
    It's a great day to be alive...
     
  13. Danno

    Danno 1/2 ton status

    Joined:
    Aug 4, 2001
    Posts:
    487
    Likes Received:
    0
    Location:
    Rockford, IL
    Yeah, that's what I think the deal is. I'm going to NAPA tonight and picking up a brush set and bearings, maybe a regulator if they're not too expensive.

    If I get this done right, I'll be able to afford new belts for my engine! :-)

    1984 K5 Blazer 4x4 Silverado
    6.2L diesel, 700R4, 3.42 gears, 31x10.5" tires
     
  14. coopertwpk

    coopertwpk 1/2 ton status

    Joined:
    Mar 18, 2000
    Posts:
    478
    Likes Received:
    0
    Location:
    Spring Valley Lake Ca.
    Pep girls sells the kit for 13$ and it comes with the rectifier and brushes new bearings and a couple of other parts it takes about 15 min to do the rebuild and an hour to get it off and on.

    88k5 silverado w4"lift <font color=orange>d44 and corp14ff</font color=orange> with 4.11
     

Share This Page