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Alternator question- and power usage question

Discussion in '1982-Present GM Diesel' started by mountainexplorer, Jan 17, 2006.

  1. mountainexplorer

    mountainexplorer 1/2 ton status

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    From what I have searched and read, an alternator on a 6.2 Diesel is different than a regular alternator on a gas motor. Is that a correct fact? What is it that makes them different?

    Also, since a Diesel doesn't run on spark, with the exception of power used for glow plugs, lights or other external uses of power, if an alternator is not charging, a 6.2 should keep running without discharging the batteries, and should keep running even if the batteries run low or dead unless manually shut off. Is this a correct assumption?

    My alternator appears to have quit charging, and I need to make a trip with it tomorrow and can't afford buying an alternator right now. If I make the trip during the day without using lights or other power draining accessories and don't shut it off, I think I should be able to make the trip.
     
  2. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    Hmm, well the 6.2 is a mechanical motor and I don't think it requires any electricity to run but I'm not positive on that engine. If it will run with completely dead batteries, is it a good idea? I know on our tractors that have mechanical diesels, when I shut the key off and they are still running I lose all instrumentation. Maybe if you charged the batteries up first so that way you had the guages, turn signals, and brake lights.
     
  3. mountainexplorer

    mountainexplorer 1/2 ton status

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    I wouldn't try to run it very long with dead batteries. Right now I have them charging so that tomorrow, even if I have to use a fair amount of power for whatever comes up (lights, gauges, wipers etc) that I'll have enough juice to keep my taillights functional the entire time. I have a couple stops to make and I'll just leave it running so I won't have to use glow plugs or the starter. I was mainly wondering, in the event that they do go nearly or totally dead that I could probably still make it without the motor stalling like a gas engine would.

    I have a regular alternator, and it looks externally pretty much the same as the one on the diesel, but I'm under the impression that they are different. Not sure why though.
     
  4. afroman006

    afroman006 1/2 ton status

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    The 6.2 needs one ignition hot wire to the injection pump to run, nothing else electrical. I dont know how much power that lead needs but it cant be much. When I was in Clayton, Oklahoma, I got seperated from my club and drove about 20 miles down a logging road before I realized my alternator wasnt charging. I have a 6.2 with no frills, but I do have electric fans. I managed to make it back to the trailhead on my two walmart cheapo batteries but when I finally pulled onto the trailer you could hear the electric fans dying. Motor was still running like a champ.
     
  5. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    During my trip back from Texas almost 5 years ago my alt packed it in leaving Round Rock. It was night time, headlights on, radio on, 2 sets of tail-lights on and a 350 with HEI. It ran for over 2 1/2 hours on the freeway before the lights got too dim to help at all. Finally stopped in italy TX and replaced the alt in a parking lot.

    Without headlights I think a 6.2 would go for weeks as long as you didn't have to start it a bunch of times.

    Rene
     
  6. imiceman44

    imiceman44 1 ton status

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    Like you know so far, the 6.2 needs power to the IP which is not much so if you are running during the day with minimal use of light towrds the end of the day or a few occasionnal uses of wipers (don't underestimate those) you will be fine.
    One thing do not forget with dead batteries you can't shut the motor off, that is electrical too.
    You can run for a week at least with dead alt and a full charge of batteries during the day and I have done it.
    IceMan
     
  7. 6.2Blazer

    6.2Blazer 1/2 ton status

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    Years ago before I really knew any better, I was out of town and noticed the voltage gage was showing lower than normal but didn't think anything of it. I drove a short distance at night with the lights on, stopped and restarted the engine a couple of times, and started the truck the next morning and drove 2 hours back home. Once home I popped the hood and noticed the alternator belt was missing. I then started the engine again and drove 15 minutes away to the parts store for a new belt.......never noticed the batteries sounding like they were struggling when starting the engine.
     
  8. kennyw

    kennyw N9PHW Premium Member

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    But don't forget your brake lights and turn signals do not work when the batteries do finally go dead!
     
  9. kennyw

    kennyw N9PHW Premium Member

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    I have an extra used alternator incase you need to wait till this weekend to replace it?
     
  10. diesel4me

    diesel4me 1 ton status Premium Member

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    Mine looks the same..hmmm??

    My 82 6.2 (or whatever year motor is in it!) has a normal looking 10SI Delco in it,looks just like any other GM gas motor altenator...but then I've never really looked that closely either..is it different bolt pattern,pulley lineup,or what IS the difference??...:confused:

    If they are different,I'd better start looking for a spare,just in case..but I bet all the "guts" are the same inside...:crazy:
     
  11. kennyw

    kennyw N9PHW Premium Member

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    I know the case is the same... might have a different rotation between the 2 halves though. Possibly a higher amp output to compensate for the higher draw starter. But in a pinch I would have no trouble throwing a gas version alternator on the truck and running it.
     
  12. imiceman44

    imiceman44 1 ton status

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    The case is the same, but the part numbers are different, and I believe the difference is in the regulator, it kicks in at a lower RPM.
    I have put a high amp alt from a gas truck and it worked fine.
    It was a 125AMP output
     
  13. mountainexplorer

    mountainexplorer 1/2 ton status

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    Mine is just doing weird things. Gauge reads 10-11... then after driving on the highway it climbs to 12 then 13 then just above 13 where it normally sits at. Then it slowly would fluctuate at random back down to 11, then up to 14. Didn't seem to matter whether the lights were on or not, it decided to charge and discharge whenever it wanted too.

    It also was acting up weird last week, stalling out all the time when it would drop from a higher rpm to idle. Instead of going back to idle it would just die. I threw in some of that Diesel fuel additive and then it stopped stalling... then started stalling again... then stopped stalling... then started again, and at final when I pulled back to the house tonight with bright headlights and 11 volts on the gauge... it wasn't stalling anymore again.
     
  14. kennyw

    kennyw N9PHW Premium Member

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    Sounds like it may be time to change the fuel filters... My dually was acting like that and turned out to be a small inline filters that plugged up.
     
  15. diesel4me

    diesel4me 1 ton status Premium Member

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    almost sounds like icing!..

    The symptoms you describe almost sound like carb icing on a gas motor!..was it cool and rainy last week up there??..I wonder if diesels can "ice up"..dont see how they could, with that huge "hole" open in the intake ,but maybe the air filter itself got wet or icy for awhile,and choked the air supply off??..

    I'd give your fusible links,the red 10 ga wire to the altenator "stud", and battery cables a good looking over too..I've seen quite a few "half fried" fusible links from a wire fire previously,(usually from a hack installed stereo system,or a positive cable melting to an exhaust manifold) that partly melted them,and have only a few strands still making contact,and they can heat up and break the connection intermittently
    ..also check the wires from the 2 prong plug at the alternator for power at both while its running..might be the brown or white wire from the #2 terminal on that plug isn't energizing the field all the time like it should,because its gangrene somewhere ,or shorted to ground intermittently..

    Sometimes when the diode trio loses one diode it will still charge,but at a lower rate..or cut out once in a while...(usually makes the "ALT" light glow dimly at night,or flicker, when the diode trio is going south!)..

    I've yet to change my fuel filter,and its the same one that was on my truck when I got it 2 years ago..:blush: ..I only put 800 miles on it since I got it ..I'm sure its due though!..:rolleyes: ..only put 5 gallons in it so far since november.:eek1:


    Well,at least the 10+ spare altenators I have collecting dust off gas motors will bolt on my diesel and work if need be..I have a few 66 amp and a 63amp,and few 55 amps..should be big enough,I looked at the one on my truck today,and its a 66 amp..looks original too..:ooo:
     
  16. Roz

    Roz 1/2 ton status

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    the difference in the alt in the diesel is made for low rpm, gas is higher. it would prolly work but not for all the lights and freq. starting. to "get by" would prolly be ok just a guess but it would prolly be about a 10th of normal output
     
  17. DieselDan

    DieselDan 1/2 ton status

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    Intersting....:thinking:

    This is the first I've heard about the diesel altenators being different. I do know that the diesels used the older SI model altenators long after GM switched to the new CS style. My '89 has the older SI.

    I had my altenator rebuilt years ago, but I never told the rebuilder it was for a diesel. Too bad, if there were any differences (as far as low RPM/output) he would have known about :doah: (guy was a wizard).
     
  18. maynardogle

    maynardogle 1/2 ton status

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    I had an alternator that wandered around in voltage like yours is. It wasn't always dead ...so I limped around for over a year with it. When I finally took it rattled..so I took it apart and a chunk of the potted diode assembly fell out..... I replaced it and the wandering voltage went away. A good alternator should just sit there at 13.8-14.4 anytime the rpms are over 1000.
     
  19. Roz

    Roz 1/2 ton status

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    well i guess this is going to require more research. i have a diesel alt and gas at home. ill have to take a gander at em.
     
  20. 6.2Blazer

    6.2Blazer 1/2 ton status

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    My '90 with the 6.2 came from the factory with a 12SI unit. When it finally died I installed a 140 amp CS144 version on it, exact same version that is used on gas engines. The adaptor plug and the basic modifications to the brackets were the same as if you were converting a gas engine from one style of alternator to the other.

    I'm not sure about the regulator or engine rpm questions. Granted, the 6.2L has a lower max. rpm rating then a gas version engine, but you are running the same rpm range during normal operation whether it's a gas engine or the 6.2L. Think about it, the 6.2 equipped trucks came with the same transmission, transfer case, and gears to a gas truck which equals same engine rpm for all speeds. Even if the gas engines can run 1,000-1,500 rpm higher for the maximum rpm, it's not like those engines see 5,000+ rpm for any length of times during normal driving.
     

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