starter question

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by rustymike, Jan 14, 2022.

  1. rustymike

    rustymike Bobtail Member

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    Hey everybody. Finally Friday. I have a 2015 KW T880 day cab. The batteries are in the cab under the
    passenger seat. The cable's run to a battery switch then under the cab to two lugs under the drivers side.
    From the lugs to the starter. I replaced the batteries, cable's and the starter. The cable's run from the battery switch to the starter, bypassing the lugs. This truck was added to the fleet a year and a half ago, and has always had a slow cracking problem. All the new parts fixed the problem. Now its's cranking slow again.
    The driver knows he has to turn the battery switch off at the end of his day, but I'm sure there's a draw somewhere I'll have to find. My question is, if battery voltage is decreased will that increase amperage to the starter and burn it up?
     
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  3. rogermunn1

    rogermunn1 Light Load Member

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    Yes , lower amperage will cause starter to drag and eventually burn it up . Take off ground cable side of the batter and put a test light between the negative side of battery and other end to negative cable . If it lights up you have a draw . Start unplugging fuses one at a time and when the light goes out thats the draw
     
  4. BoxCarKidd

    BoxCarKidd Road Train Member

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    Use an old school test light with a bulb in it. Some of these new deals require near no draw to light. The memory wire for some radios can glow the bulb but not really draw much. Unhook that first. I have used a lot of amp clamp deals and such but always go back old school.
    Some of the Petes here have had problems with poor battery cables. Petes and KWs are both paccar. Normally voltage drop tests tell the deal cold but we seemed to have more issues when hot. Where did you buy your cables?
    There is a starter post going on at the same time. Some wore out guy put me on a Denso gear reduction starter. That helped a lot on the C15's. Cannot tell those folks if it will fit on all those other trucks and engines
     
  5. rustymike

    rustymike Bobtail Member

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    Dec 17, 2021
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    I definitely have a draw somewhere, probably two. Disconnected the ground cable and put a test light between the battery and the cable. I unplugged all the fuses under the hood and under the dash one at a time and the light never went out. The shop has spools of cable and had to make positive and negative
    cables. I don't have an old school test light but I'm sure I can make something with a flashlight bulb. I will disconnect the radio before I start pulling fuses again. Thank you for the help on this.
     
    Rideandrepair Thanks this.
  6. AModelCat

    AModelCat Road Train Member

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    Canuckistan
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    Starter will always draw X amount of watts. If voltage is low, the starter will pull more amps. Amps = heat.

    Watts = Volts × Amps

    If voltage is low, there needs to be more amperage to maintain the amount of watts the starter uses.
     
  7. rustymike

    rustymike Bobtail Member

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    Dec 17, 2021
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    So, the bottom line for me is to find out where the voltage drain is and eliminate the need for more amps ?
     
    Rideandrepair Thanks this.
  8. rogermunn1

    rogermunn1 Light Load Member

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    Tell me more about these gear reduction starters for Cat C15 , mine takes alot of grunt to get her spinning.
     
    Rideandrepair Thanks this.
  9. rogermunn1

    rogermunn1 Light Load Member

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    Forgot to mention old school test light. good call. Actually when i key my CB it will light my old school test light laying on the floor. But thats a whole other thing. Broadcasting Watts lol
     
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  10. BoxCarKidd

    BoxCarKidd Road Train Member

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    I thank I still have one of these starters on the shelf. Will try to remember to look and get a part number. Put one in stock for replacement as needed. All of those trucks are gone except one.
     
    Rideandrepair Thanks this.
  11. xsetra

    xsetra Road Train Member

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    39mt is the gear reduction, 42mt is the normal starter
    I don't know if spacers are needed on the cat motor. Also make sure you have the correct tooth count
     
    Rideandrepair Thanks this.
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