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Another alternator question

Discussion in 'Chevy Trucks' started by 70monte, Jan 23, 2009.

  1. 70monte

    70monte Senior Member
    Messages: 468

    My 98 K3500 has the optional 124amp cs144 case alternator. When I first start the truck when its cold, the volt gauge shows over 14 volts. As I drive, the volt gauge goes below the 14 volt mark and usually stays at the mark right under the 14 volt mark. Today it went two marks under the 14 volt mark. The last time I checked it with my scanner, it showed 13.7 at idle but I don't remember if the truck was hot or not. This is a used alternator that supposedly has approx. 57,000 miles on it.

    Does this indicate a charging problem? The truck always starts and it never feels like the battery is drained.

    My 98 K1500 has the 105 amp cs130 case alternator, which is fairly new and it stays over 14 volts all of the time whether the truck is hot or cold.

    What is the lowest voltage that would be normal for the 124 amp alternator. Thanks.

  2. T-Trim

    T-Trim Senior Member
    from NE OH
    Messages: 207

    What is the output at 13.7?
  3. 70monte

    70monte Senior Member
    Messages: 468

    I don't know. I haven't tested for the output yet. Monday will probably be the next time I have time to look at it. Thanks.

  4. augerandblade

    augerandblade PlowSite.com Addict
    Messages: 1,054

    tymusicussmileyflagI dont think you have a problem, the batterys are getting recharged when it a 14V and yes I noticed on my Chev that the guage gets lower as the truck/batteries warm up[ and batterys get charged. I think that 13.9 V on the volmeter whether on guage or tester is the correct setting. This morning here it cold overnight -25C starrted one of my plows up and yes it was up over 14V when I was using the plow I noticed that the battery light came up on my dash. So I swithch to Low 4 wheel to get the revs up and after 20 min the dash lite was quiet.Just my .02s worth
  5. 70monte

    70monte Senior Member
    Messages: 468

    OK, thanks for the info. I will keep an eye on it and try to see how many amps and volts its putting out when hot.


    MAR4CARS Senior Member
    Messages: 246

    You need to measure amps under a load. You can have 14.7 volts all day long but crap for amps.
  7. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    Altenators definitely have better voltage output when cold. As long as your voltage is above 12.6, your altenator is keeping with the load you are putting on it. You can't take much stock in those factory gauges for an actual specific value. You can use them however to keep an overall eye on things. If you notice a big change on a gauge, check it out.
  8. 70monte

    70monte Senior Member
    Messages: 468

    Thanks for the replies. I guess I'm just comparing the gauge to my 98 K1500 which never goes lower than the 14 on the gauge. Of course it has a fairly new alternator in it while the K3500 has a used one in it. I went ahead and bought the new reman AC-Delco 120 amp alternator just in case. It was only $85 which is a lot cheaper than I found anywhere else. Its been so cold and icy here lately that I haven't been able to check out the truck. I did notice that its leaking coolant on the ground and it appears that the water pump is leaking now. It appears that I will have a few projects to complete on this truck when it gets warmer.