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  1. #1
    Bronze Member
    Join Date
    Mar 2002
    Posts
    60
    Location
    Tx
    Tractor
    NH TN75DA

    Default TN 75D Alternator Question

    Ok, I need to run a question by you professionals. My tractor is in the shop for some maintenance and sensor malfunction. They tell me the alternator is charging off and on. They remove it and take it to an alternator shop to get it checked out. Find out today that the alt. shop hooked it up said nothing was wrong with it. NH mechanic puts it back on and says when the rpm's are below about 1600 it's not charging all the time and when it goes above that it charges fine. So I talk to the mechanic today and he gives me a couple options. 1. leave it alone and if the battery light comes on just make sure you have rpm's high enough to kick it off (which all of my mowing of course is above that 1600) and he says it may last 10 months or 10 yrs. says this is what he would do if it was his. 2. Replace it with a rebuilt alternator which they said is almost $500. Cheapest I've found on line is $395. I was told that if something had been wrong with it the alt. shop they could rebuild it for about $75. Mechanic thinks that the alt. shop hooked it up to their electric motor and it probably simulates something over 1600 which shows it's working correctly. I think I'm going to have the service mgr. call the alt. shop and see if they will just open it up anyway and replace whatever they replace when they rebuild them and then put it back in the tractor. That way at least the insides are replaced and if it works.. great and if not, I'll just keep it high enough for the light to stay off. Sorry for the length...Any other ideas?? I find plenty of replacement alt.s online the say for the TN75D, but they are 45 or 65 amps. Mine is 85 and can't find anything but NH rebuilds.

    Thanks in advance for your comments and suggestion..

  2. #2
    Platinum Member
    Join Date
    Mar 2008
    Posts
    547
    Location
    Colorado
    Tractor
    TN55

    Default Re: TN 75D Alternator Question

    Take a look at the alternator and at online 'images' (do a search for the alternator, then select the 'images' option on the top left edge). I bet you find out who made that alternator. Then you can search on that brand and find out what else uses that general model. Cars, trucks, motorcycles usually buy from someone else. An NH version may be insignificantly different. I found that with Volvo and other European cars, Subaru & Japanese, Triumph & Kawasaki & Suzuki. I wouldn't be at all surprised that it is Japanese. The alternator shop could tell you.

  3. #3
    Bronze Member howierd3866's Avatar
    Join Date
    May 2008
    Posts
    61
    Location
    South Florida

    Default Re: TN 75D Alternator Question

    all my tractors as long as its over 700 rpm its charging....as for a new alternator just have the alternator rebuild it for $75.00 thats all we do.... in over 30 years never bought new one...good luck

  4. #4
    Platinum Member
    Join Date
    Mar 2008
    Posts
    547
    Location
    Colorado
    Tractor
    TN55

    Default Re: TN 75D Alternator Question

    This reminded me of a conversation I had a year or so ago with my local (former NH, now JD) dealer. My TN55 shows the 'not charging' warning light on the dash when started until I rev it up a bit. It goes off, then I let it idle down.

    He said he remembered there was a software update that is supposed to fix the false warning. Not sure if this is true or applies. Worth checking it out.

  5. #5
    Bronze Member
    Join Date
    Mar 2002
    Posts
    60
    Location
    Tx
    Tractor
    NH TN75DA

    Default Re: TN 75D Alternator Question

    Thanks mojo..just saw your post...I'll run it by the service guy...

  6. #6
    Super Member RickB's Avatar
    Join Date
    Sep 2000
    Posts
    7,400
    Location
    Eastern NY
    Tractor
    Case 885, Ford 4000

    Default Re: TN 75D Alternator Question

    motorjock, I agree completely with your NH mechanic, I've seen this exact thing as well. Some guys live with it indefinitely, some swap out the alternator. Replacing diodes within your alternator probably will cure it. I agree the alternator shop probably didn't do a slow speed test.
    We have too much gun control.
    What we need is more idiot control.

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