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7020 alt light comes on above idle

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Leon B MO View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Leon B MO Quote  Post ReplyReply Direct Link To This Post Topic: 7020 alt light comes on above idle
    Posted: 07 Nov 2017 at 10:13am
Started it the other day and noticed the alt light got brighter with higher rpm's. I chopped stalks for 3 hours with fan on, seemed to be ok. What do I look for, could it be overcharging?
Thanks
Leon B Mo
Uncle always said "Fill the back of the shovel and the front will take care of itself".
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DougS View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DougS Quote  Post ReplyReply Direct Link To This Post Posted: 07 Nov 2017 at 10:31am
Put a voltmeter on the battery. It's overcharging if the voltage is 14.5+ volts. It isn't charging adequately if it's much below 14 volts. It seems to me your problem is a wiring issue. Check the voltage first.
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Gerald J. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gerald J. Quote  Post ReplyReply Direct Link To This Post Posted: 07 Nov 2017 at 1:52pm
Usually the alternator light is in the wire that starts the alternator excitation and once the alternator fires up the light goes out because it has 12 volts on both sides. Sounds like the power source for the light isn't there.

Gerald J.
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JoeO(CMO) View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JoeO(CMO) Quote  Post ReplyReply Direct Link To This Post Posted: 07 Nov 2017 at 4:31pm
have you checked the belt?




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Steve in NJ View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Steve in NJ Quote  Post ReplyReply Direct Link To This Post Posted: 07 Nov 2017 at 4:58pm
Loose belt...... Check it out.
39'RC, 43'WC, 48'B, 49'G, 50'WF, 65 Big 10, 67'B-110, 75'716H, 2-620's, & a Motorhead wife
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Post Options Post Options   Thanks (0) Thanks(0)   Quote wekracer Quote  Post ReplyReply Direct Link To This Post Posted: 07 Nov 2017 at 8:42pm
3rd on loose belt.
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MACK View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MACK Quote  Post ReplyReply Direct Link To This Post Posted: 07 Nov 2017 at 9:30pm
Light comes on above idle because of a bad diode or rectifier bridge. MACK
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Leon B MO View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Leon B MO Quote  Post ReplyReply Direct Link To This Post Posted: 08 Nov 2017 at 7:43am
Belts are fine, where would I find the diode or rectifier, inside altenator?
Leon
Uncle always said "Fill the back of the shovel and the front will take care of itself".
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DougS Quote  Post ReplyReply Direct Link To This Post Posted: 08 Nov 2017 at 7:45am
What kind of alternator? Is it a Neihart? It's the fact that the light gets brighter as the engine speeds up that puzzles me. Neihart alternators are a strange breed. I'm somewhat familiar with how they work and I know that conventional wisdom does not apply.


Edited by DougS - 08 Nov 2017 at 7:47am
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Leon B MO View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Leon B MO Quote  Post ReplyReply Direct Link To This Post Posted: 08 Nov 2017 at 8:02am
Don't know off hand the brand but the tach rpm's are measured by sensor in alternator, so not any alternator will work.
Leon


Edited by Leon B MO - 08 Nov 2017 at 8:03am
Uncle always said "Fill the back of the shovel and the front will take care of itself".
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Gerald J. View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gerald J. Quote  Post ReplyReply Direct Link To This Post Posted: 08 Nov 2017 at 8:10am
All alternators generate Alternating Current voltage and then rectify that with internal rectifiers to produce DC for battery charging and DC equipment on the machine or vehicle. The tachometer can use the frequency of that alternating current voltage to read out engine speed. Not all alternators bring out the AC voltage for the tachometer. And the alternator pulley diameter has to be the same as well as the internal alternator construction has to have the same number of rotor poles to generate the same frequency proportional to engine crankshaft speed.

In early alternator days there were alternators that used external rectifiers.

I suspect the feed wire to the alternator lamp is not connected to the battery but has broken and has gotten connected to ground. It should be connected to the battery with the ignition switch so its disconnected when the engine is shut down.

Gerald J.
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Leon B MO View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Leon B MO Quote  Post ReplyReply Direct Link To This Post Posted: 08 Nov 2017 at 8:24am
Thanks Gerald, I'll start there.
Leon
Uncle always said "Fill the back of the shovel and the front will take care of itself".
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DougS Quote  Post ReplyReply Direct Link To This Post Posted: 08 Nov 2017 at 10:06am
Neiharts use an internal generator and regulator to control the field of the alternator. They are a bit peculiar, and expensive.
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CAL(KS) View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CAL(KS) Quote  Post ReplyReply Direct Link To This Post Posted: 08 Nov 2017 at 10:12am
arnt they Neihoff? not Neihart?
Me -C,U,UC,WC,WD45,190XT,TL-12,145T,HD6G,HD16,HD20

Dad- WD, D17D, D19D, RT100A, 7020, 7080,7580, 2-8550's, 2-S77, HD15
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DougS Quote  Post ReplyReply Direct Link To This Post Posted: 08 Nov 2017 at 10:16am
Whichever. As long as it isn't a Newhart. They cancelled him.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CAL(KS) Quote  Post ReplyReply Direct Link To This Post Posted: 08 Nov 2017 at 10:19am
lol my wife makes me watch reruns off youtube with her
Me -C,U,UC,WC,WD45,190XT,TL-12,145T,HD6G,HD16,HD20

Dad- WD, D17D, D19D, RT100A, 7020, 7080,7580, 2-8550's, 2-S77, HD15
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MACK View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MACK Quote  Post ReplyReply Direct Link To This Post Posted: 08 Nov 2017 at 9:59pm
7020 should have a Delco. In todays world, it may be cheaper to go to local auto supply and buy a alternator than pay some one to check and repair the one you have.     MACK
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JoeO(CMO) Quote  Post ReplyReply Direct Link To This Post Posted: 08 Nov 2017 at 10:29pm
Originally posted by DougS DougS wrote:

Whichever. As long as it isn't a Newhart. They cancelled him.
Don't be poking fun at Newhart..he was funny without a garbage mouth
 
 
 




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Post Options Post Options   Thanks (0) Thanks(0)   Quote LeonR2013 Quote  Post ReplyReply Direct Link To This Post Posted: 08 Nov 2017 at 10:34pm
If you do buy another alt. get a 21SI. All the rest of them are J.U.N.K.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JoeO(CMO) Quote  Post ReplyReply Direct Link To This Post Posted: 08 Nov 2017 at 10:52pm
Do the headlights come on ok and keep the same brightness all the way to full throttle up and stay that way? or dim until you bring it back to idle?
 
When the lamp comes on what is happening to the alternator belt?  Does it keep its tension all the time or does it start to show slack?  Does it track good, consistently or want to come off?
 
How about the alternator pulley, is it true all the way in or grooved?
How is the belt for wear and cracks, is it smooth and shinny, can you see the cord in the belt?
 
The alternator  takes a lot of power and the belt requires GOOD friction to drive at high speed and when they get warm the tend to stretch.
Does the tach drive from the alternator ?  does it indicate correct speed or is it dancing  around like its looking for a number to land on? 




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Leon B MO View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Leon B MO Quote  Post ReplyReply Direct Link To This Post Posted: 09 Nov 2017 at 10:20am
Belts are tight ang only 2 years old, the tach is not jumping, seems to follow the actual rpm's pretty close. I'll put a volt meter on it first if it's not over 14.5 or so I'll look into a bad wire at alternator light. I can test to see if it's charging by turning off the battery cut off since it has electric solenoid at injection pump. I forgot about that.
Thanks for all the suggestions.
Leon B Mo
Uncle always said "Fill the back of the shovel and the front will take care of itself".
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DougS Quote  Post ReplyReply Direct Link To This Post Posted: 09 Nov 2017 at 11:11am
Yikes!  Do NOT run the alternator with the battery disconnected!
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Leon B MO View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Leon B MO Quote  Post ReplyReply Direct Link To This Post Posted: 09 Nov 2017 at 11:46am
If the alternator is bad and not charging, tractor will die instantly, if tractor continues to run , I'll turn battery cut off back on within 5 seconds. Will that hurt anything?
 
Leon B Mo
Uncle always said "Fill the back of the shovel and the front will take care of itself".
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HoughMade View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote HoughMade Quote  Post ReplyReply Direct Link To This Post Posted: 09 Nov 2017 at 12:19pm
This isn't a permanent magnet alternator is it?  Where is the rotor going to get the electricity to be an electromagnet?  
1951 B
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian Jasper co. Ia Quote  Post ReplyReply Direct Link To This Post Posted: 09 Nov 2017 at 12:53pm

Since Mack says it should have a Delco, repair kits can be had off the internet usually about $30. I'd say with the light on and still keeping the battery up, the diode trio is probably bad.

"Any man who thinks he can be happy and prosperous by letting the government take care of him better take a closer look at the American Indian." Henry Ford
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DougS Quote  Post ReplyReply Direct Link To This Post Posted: 09 Nov 2017 at 7:12pm
Originally posted by LeonR2013 LeonR2013 wrote:

If you do buy another alt. get a 21SI. All the rest of them are J.U.N.K.

Why such a mammoth alternator? I'm not certain, but the SI series probably doesn't have a tap off the diode pak that would work as a tach signal.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote LeonR2013 Quote  Post ReplyReply Direct Link To This Post Posted: 09 Nov 2017 at 7:57pm
Dang, I've got my diagrams down at the shop and don't think I'll get out to go get them. But that may right, so you'd be best to check that out before getting any alt.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Acdiesel Quote  Post ReplyReply Direct Link To This Post Posted: 09 Nov 2017 at 9:04pm
THAT HAS A MECHANICAL FUEL PUMP SHUT OFF SO EVEN IF YOU UNHOOK THE BATTERY IT WILL STILL RUN.

GET A VOLTMETER AND CHECK OUTPUT.

DAN
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DougS Quote  Post ReplyReply Direct Link To This Post Posted: 10 Nov 2017 at 5:24am
Originally posted by Acdiesel Acdiesel wrote:

THAT HAS A MECHANICAL FUEL PUMP SHUT OFF SO EVEN IF YOU UNHOOK THE BATTERY IT WILL STILL RUN.

GET A VOLTMETER AND CHECK OUTPUT.

DAN
Which tells you little or nothing with the alternator not under a load. Doing this may well blow what's left of the diodes.  Unloaded alternators can produce voltage spikes well in excess of 100 volts. He knows the alternator has an output. He's measuring 14.5 volts under load. It's a matter of figuring out why the light is coming on. If a single diode is bad you'd generally only see it with an oscilloscope. If the wiring is good take the alternator to a rebuilder - one that offers a warranty with his work. Of course you can purchase a rebuilt alternator, but if it has a different number of poles the tach will not be accurate.
 
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