'76 alternator output voltage?

Discussion in 'Electrical Systems' started by UFC284P, Jan 31, 2010.

  1. UFC284P

    UFC284P New Member

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    Hi; first post on here-from the amount of info available on this site,it looks like I'll be a regular visitor!
    I have just imported a lovely Firethorn orange '76 from Ohio back here to the UK.Fantastic car.I could have bought one of the many abused Firebirds that are over here,but wanted something rarer & with more class!!!
    Few jobs to do (saggy headliner,coolant loss from one headgasket) but the first one was the ignition lamp glowing faintly or brightly.I have fitted a replacement(Hella factory exchange) alternator;no more warning lamp glow, but when checked at either the bolt-on terminal or the red wire in the 2-pin plug,it is putting out around 14.8 volts. I would have liked to see around 14.2v.
    Does this sound too high/like it may be an issue?
    :) Thanks.

    Oh;it also has a strange graunching sound over bumps that comes from behind the speedo (as if a bolt is being pulled through the firewall)-suspension/brake booster etc all look good.Anyone heard anything similar?
     
  2. Twisted_Metal

    Twisted_Metal Administrator Staff Member Lifetime Gold Member

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    Since you're testing it directly from the source... You don't have any wiring resistance which all of the rest of the things in your car will have.
    I doubt 14.8 volts will cause any problems at all.

    If it was 16-17 volts (or more)... I would be worried about the life expectancy of the ignition module in the distributor.
    (Ignition modules are probably the most sensitive piece of electronics in these old cars and they don't like high voltage.)

    Check the front suspension, shocks and the body/frame mounts for the source of your noise.
    Problems in those areas could be serious. (But not at all impossible to repair.)

    And WELCOME to NastyZ28! :D :cool:
     
  3. UFC284P

    UFC284P New Member

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    That was quick! Thanks for prompt reply. Will keep an eye on the output; Although badged an LT,it was built a sport & has only idiot lights on dash. I have additional 52mm gauges (tacho/water temp/volts) to mount discretely under the radio. Appreciate your help.
     
  4. Gary S

    Gary S Administrator Lifetime Gold Member

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    Don't worry about 14.8 volts. You need it to get the battery fully charged, and if the weather is cold, 14.8v won't even be enough. GM designed their solid state regulators to that their output voltage is temperature dependent. The colder the weather, the higher the output voltage. Batteries require increasingly higher voltages to accept a charge as the temperature of the electrolyte goes down.
    A lead acid battery cannot be charged below 0 degrees F, so the only way to charge it when it gets that cold is to heat the electrolyte first until it gets above 0. That is done by the alternator with its higher voltage passing through the electrolyte and the resistance of the electrolyte causing heat.
    My daily driver alternator puts out over 16 volts in extreme cold here in the winter, and it has worked very well that way for almost 30 years. It never lets the battery go dead even at temperatures down to -40, so GM knew what they are doing.
     

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