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.

Alternator help?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Batchman, Jun 20, 2002.

  1. Batchman

    Batchman Registered Member

    Joined:
    Apr 9, 2002
    Posts:
    54
    Likes Received:
    0
    Location:
    Oklahoma
    OK I just replaced the alternator from the stock 66 amp to a rebuilt 94 amp. No more fan motor running low at stop lights ect. All was good right? Until today I went through an ATM and the fan motor got really fast the volt meter went all the way to 18+ put it in drive got on the street everything went back to normal just over 13 volts where it normally sits. then at the next stop light it went back up to 18 took off and the volts dropped to about 10 fan slowed way down and felt like the truck was going to die. So I shut off the ac crippled it to Autozone, tried to explain to the guy what happened he would not here it hooked up his machine and told me he can not test the alternator because it is not hooked up? I told him to look at the wires that it is hooked up and he told me sorry he can't help. I asked him to test it with a load on it ac, lights he said no it will not help? Is this guy right what would cause it to spike like that?
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,975
    Likes Received:
    189
    Location:
    Roy WA
    Bad voltage regulator the only thing I can think of.
     
  3. random

    random Registered Member

    Joined:
    Jun 12, 2002
    Posts:
    13
    Likes Received:
    0
    Location:
    maine
    Sounds an awful alot like a bad regulator to me. As long as all grounds are good and connectors are tight.Have had many bad experiences with rebuilt alternaters.went though 6 once to get a good one!!!! Imrunnin a rebuild alt off an 87 park ave 105 amps.
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,975
    Likes Received:
    189
    Location:
    Roy WA
    I rebuild them myself now, $15 kit and your back in business. Not sure at what point the aftermarket will stop trying to be ultra cheap and actually institute some Quality Control.
     
  5. Batchman

    Batchman Registered Member

    Joined:
    Apr 9, 2002
    Posts:
    54
    Likes Received:
    0
    Location:
    Oklahoma
    I tried rebuilding the one before I bought this rebuilt one and could not get it to work I also cracked the case. Does anyone know why the computer would read that the wires are not hooked up?
     
  6. Batchman

    Batchman Registered Member

    Joined:
    Apr 9, 2002
    Posts:
    54
    Likes Received:
    0
    Location:
    Oklahoma
    Also I checked the grounds by using the + terminal and my 12 volt light with pointy screwdriver looking thing? anyway they all would ground out and light up the light bulb. Is that how you check a ground?
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,975
    Likes Received:
    189
    Location:
    Roy WA
    What year are we dealing with? (hint: profile)

    To check my alternator, I either check the voltage going into the battery (anything over 12 with the heater on high, at idle, with the headlights on and I'm happy) but if I'm real concerned (like the last time the alternator appeared to die) I checked voltage coming off the single red wire on the back of the alternator case. Something like 10 there is a bad thing.

    Don't forget, although not likely you are running this low, if your RPM's drop enough (maybe to 500 or so) the alternator output will greatly drop.

    Voltmeter is a necessary tool when doing this kind of testing.
     
  8. Batchman

    Batchman Registered Member

    Joined:
    Apr 9, 2002
    Posts:
    54
    Likes Received:
    0
    Location:
    Oklahoma
    It's an 86 Chevy burb 350 I do have a cheapy volt meter from walmart at idle I was getting 12 volts from the single red wire? But I know I'm not getting 12 to the fan motor because it is turning so weakly. Also it is not RPM related cause there no change at highway speed(after all this strted today


    One more question should all 3 wires have 12 volts at idle?
     
  9. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,975
    Likes Received:
    189
    Location:
    Roy WA
    12 is pretty low. Too low to actually CHARGE the battery. Is that under "load"? (heater on, headlights on) If you bump the idle up while watching the hand held voltmeter, it doesn't change at all? That would lead me to suspect voltage regulator as well if not.

    The fan is very sensitive to voltage, even one volt additional will audibly speed it up immensely, ESPECIALLY when its on high, since its getting whatever the system gets...on other speeds, the fan gets lower voltages..high speed on the fan is directly proportional to alternator output.

    Not sure on all three wires, only worry about the battery and single one on the back of the alternator myself.

    Theres an alternator test that has to do with sticking a paperclip in the back of the alternator or something, and measuring output then, but I don't recall where I've seen that.
     
  10. Batchman

    Batchman Registered Member

    Joined:
    Apr 9, 2002
    Posts:
    54
    Likes Received:
    0
    Location:
    Oklahoma
    I relized the fan motor was very sensitive to volts being put out when my volt meter pegged at over 18 volts I had the fan on high and if felt like I had the windows down at 70 mph it was blowing that hard Would be nice to have that much blower power all the time without frying the rest of the system
     
  11. rebel222

    rebel222 Registered Member

    Joined:
    Aug 21, 2000
    Posts:
    58
    Likes Received:
    0
    Location:
    Louisiana
    I'm almost certain that is you voltage regulator. The guy at autozone must not have known how to hook up the tester. I would take that alternator back and get a new one. Bad regulator. The test with the paper clip will only work if the alternator isn't putting out any voltage. There is a test hole in the back and you stick a paper clip in the hole which touches the casing grounding the circuit, in turn bypassing the voltage regulator. Don't do this for long because you will fry something. The hole is shaped like a 'D'. But either the voltage regulator is bad or the alternator. That unit should be internally regulated, so bring it back.
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,975
    Likes Received:
    189
    Location:
    Roy WA
    If you are bypassing the regulator with a clip, how does it matter if the regulator is working right or not? Should still go to full output, right?
     
  13. Batchman

    Batchman Registered Member

    Joined:
    Apr 9, 2002
    Posts:
    54
    Likes Received:
    0
    Location:
    Oklahoma
    OK I pulled the Alternator this morning took it to the other Autozone in town and had them test it and of course it was bad anyway I told them what happened at the other store told them how the guy told me it was nt connected so he could not tell if it were bad or not. And I'm not a gripper or I would have talked to his boss I was just telling them the story. We look up the part and guess what only alternator in for the burb is at the other store. I said well how long will it take you guys to get the part because I will not go back over to that store(one of my personal principles) They said Monday I told them I would wait. Now they are looking at me like I am crazy. Again explained why I would not go back to that Autozone and the manager pulled a $30.00 higher alternator off the shelf and traded me out straight across. Now back to my personal values I will buy anything I can from that Autozone. So long store short got the Burb running again it puts out 15 volts at idle NO load and just over 13 volts with load.
     
  14. pr1aw

    pr1aw 1/2 ton status

    Joined:
    Sep 17, 2000
    Posts:
    144
    Likes Received:
    0
    Location:
    San Diego CA
    OK, I used to work at AZ. The guy didn't know what he was doing. Sounds to me like the voltage reg in the alt is crapping out.
     
  15. dyeager535

    dyeager535 1 ton status Premium Member

    Joined:
    Dec 13, 2000
    Posts:
    26,975
    Likes Received:
    189
    Location:
    Roy WA
    I'm always willing to give someone, or some place, a second chance. Thats AFTER I talk with corporate. Its not difficult, take a peak at their home page, and check out what they have for feedback options.

    I had a bad experience at a local auto parts store, after informing them what kind of $$ they get out of me annually, and what kind of service I was the recipient of, and how shoddy the store looked, I received a very nice letter in the mail, as well as two $20 gift certificates.

    Believe me, I didn't do it for the free money, but it didn't hurt. But since I took the money, and they seemed genuinely concerned about the incident, I felt that I *owed* that store a second chance. And when I went back, things were MUCH changed.

    You have to remember, employee turnover in those stores is fairly high, (so one bad employee may only be there a week or so) but if you go there long enough, you'll see the "old timers", they'll get to know you, and you will have pleasant dealings every time you go in and deal with that person.
     

Share This Page