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charging system

Discussion in 'Chevy Trucks' started by kashman, Feb 2, 2008.

  1. kashman

    kashman PlowSite.com Addict
    Messages: 1,070

    ok heres the deal 1995 chevy 2500 4-4 5.7v8. Iv put in a new batt 1000cc 800cr 115 res. Ok now for the alternator i had a 105 rebuilt 2 a 150 cause the clock position didnt lineup for the up grade and i up graded the alternator wire 2 4gag. All the plow wires are new 4gag . OK now for the problem when im stopped the truck drops 2 11 volts with the heat or the lights on hit the gas its all good stop at a light all bad mind you this is without using the plow
     
  2. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Not unheard of at all. Many "upgraded" alternators actually put out less amps at low speed than a stock alt. To get more amp without loosing the low RPM charging capacity takes a quality built alternator. Thats why some are lower cost than others. The low output at idle is usually compounded on the TBI GM's since they idle so low in gear.
     
  3. kashman

    kashman PlowSite.com Addict
    Messages: 1,070

    so shoud i get a smaller pully for the altr
     
  4. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    You could try finding a smaller pulley for the alt. But the stock pulleys are pretty small to begin with so it may not be an easy find.

    Ideally the proper thing to do is spend the money on a top quality atl to begin with. Not something guys want to hear but you do get what you pay for these days...usually. :)
     
  5. abbert55

    abbert55 Senior Member
    Messages: 170

    Have a local Alt rebuilder check the output at idle. If you just upped the amps on a stock Alt. it will not give good output at low RPM. GM makes a high output Alt. for these trucks (usually with plow prep or heavy duty towing pkg.) and you may need to spend the bucks for one. Be sure it doesn't have the black plastic rear cover... these are 100 Amp. Alts. See if you can find one in a salvage yard... could save a few $'s there.
    Al
     
  6. kashman

    kashman PlowSite.com Addict
    Messages: 1,070

    I had a starter alternator shop rebuild the alternator they started with a new 105 jumped it up 2 150 so what can i do now. I dont buy cheap parts so should i go 2 the junkyard and try 2 find the brackets for the bigger stock alternator
     
  7. kashman

    kashman PlowSite.com Addict
    Messages: 1,070

    ok still have old problem but i need 2 add a symptom volts dance when i put my blinker on
     
  8. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Have you actually checked it right at the battery with a volt meter?

    Likely needs all the ground wires/cables cleaned and/or replaced.

    Including the cab to engine, and engine to frame/battery.
     
  9. kashman

    kashman PlowSite.com Addict
    Messages: 1,070

    ok this is what i did truck was put on a machine alt batt tested good
    i took my ground from the batt 2 the frame
    batt 2 the engine block
    frame 2 the firewall all new i know that i have 2 have a bad ground some place but i just cant find it.
    is this all the grounds i need
     
  10. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Sounds like you have the grounds covered just fine. Did you check/clean the small one either in the thermostat housing bolt or on the bolt in the intake right next to the thermostat housing?


    Those "test machines" wont tell you squat when diagnosing a condition like this Chad. You need to check the voltage at the battery to see if it's just the gage being over sensitive itself (defective) thats causing this "dancing", or the entire system voltage is actually fluctuating under actual conditions.

    I'm betting that this issue happens when stopped/idling at a low engine speed correct? This is actually a very common thing on a TBI equipped truck with a hi output "custom" alternator as the TBI trucks idle at a very low RPM and most of these custom built hi amp alternators need enough RPM's to remain charging. In other words they may have an output of 150 amps or more at higher engine RPM's but wont stay charging very well at low RPM's.

    What happens when you give it just a touch of throttle to bring the RPM's up just a little? Does it get steady?