TRACTOR PARTS Allis Chalmers Case & David Brown Farmall & International Ferguson Ford & New Holland John Deere Massey Ferguson Massey Harris Minneapolis Moline Oliver & Cockshutt Kubota / Yanmar

TRACTOR MANUALS

Allis Chalmers	Case	Farmall IH	Ford 8N,9N,2N	Ford
Ferguson	John Deere	Massey Ferguson	Minn. Moline	Oliver

Tractor Talk Discussion Forum

O/T alternator or battery??

Welcome Guest, Log in or Register

Author

old

10-20-2007 21:08:24

Report to Moderator

In my 1980 chev truck the volt gauge reads only around the 12 volt level when 2 weeks ago it would read at around 13 volts. If I kick the RPM up it reads at 13 or so. So is it the battery going or the alternator??
Thanks just need a few good guess on this one

Hobby farm

[Log in to Reply] [No Email]

Kent in KC

10-22-2007 11:16:25

Report to Moderator

Re: O/T alternator or battery?? in reply to old, 10-20-2007 21:08:24

Learned this after replacing alternator, battery, etc. A "good, tight" belt that is more than three or four years old may slip a bit when the engine gets up to rpm. The centrifugal force stretches it out, making it 'bigger' and thus slipping a little. Generally speaking solid state electronics will either work or fail, no in between.

Belts, batteries and battery cables can degrade over time causing reduced performance.

[Log in to Reply] [No Email]

Old Magnet

10-21-2007 08:37:22

Report to Moderator

Re: O/T alternator or battery?? in reply to old, 10-20-2007 21:08:24

Check that belt again...if you can turn the alt. pulley by hand or with light load with a wrench it's not tight enough or the belt is worn.
I've lived with that on my "77" 350 since it was new. Just doesn't seem to be enough belt wrap after it passes over the smog pump pulley.

[Log in to Reply] [No Email]

TomTex

10-21-2007 07:31:54

Report to Moderator

Re: O/T alternator or battery?? in reply to old, 10-20-2007 21:08:24

Pull the battery, so the test is without cables and corrosion, etc. Oriellys or almost any of them will do a true load test on the battery. You can compare actual amps to rated amps on the battery. This is free and will end all speculation about the strength of the battery.

If the battery test OK, then pull the alternator and have it bench tested free. If both test OK, then check cables, wiring, and your guages. Tom

[Log in to Reply] [No Email]

jdemaris

10-21-2007 07:17:47

Report to Moderator

Re: O/T alternator or battery?? in reply to old, 10-20-2007 21:08:24

You can play guessing games - or you can stick a amp meter on the system to find out for sure what is going on.

Voltage only comes up after the amperage flow and demand slows down. If a battery is going bad, and is constantly absorbing a charge of current, the voltage cannot rise properly.

Not much different that a water system that can build high pressure with the faucet held wide open.

If the alternator is not working properly, it is still sort of the same situation as a bad battery. Not enough amperage is being provided to satisfy the need and let the voltage rise.

You could also have a situation where the battery and alternator are working fine, but there is an excess current draw on the system.

Very often, Delcos lose part of the diode trio and lose some charge capacity and can cause this - as well as many other things.

The whole deal could be diagnosed in 10 minutes with an ampmeter.

[Log in to Reply] [No Email]

John T

10-21-2007 06:38:43

Report to Moderator

Re: O/T alternator or battery?? in reply to old, 10-20-2007 21:08:24

Rich, Im sure you have seen me post this a hundred times but is there electrolyte above all the battery plates and no cells have a gray or milky color????? I bet you have a battery hydrometer see what each cell reads..... Its easy n free for Auto Zone or Pep Boys or Advance Auto etc to stick a load meter on the battery PLUS indicate the alternators condition. Let them do it lol while you pick up some oil etc.

Id say an accurate volt meter on a good charged battery shuld read 12.6 setting bur rise from 13 to 14.5 or so depending on RPM and state of the battery n alternator buttttt tt I wouldnt be all that concerned so long as it rises some at least cuz maybe the regulator is smarter then you think n just doing its job....I would expet it to charge more right after start up but drop off soon afterwards. Id also checked for a glazed belt n that its good n tight although thats less an issue on those serpentine types.

Tale care my Old friend

John T

[Log in to Reply] [No Email]

old

10-21-2007 10:03:52

Report to Moderator

Re: O/T alternator or battery?? in reply to John T, 10-21-2007 06:38:43

No hydormeter in the place. Cell full and the stuff looks good. I guess I'll pull a battery out of one of the tractors and see what happens. The battery was put in some time in 05 so it is getting out and I do work it hard some times with the 2 wenches I have on the truck.

Hobby farm

[Log in to Reply] [No Email]

flying belgian

10-21-2007 19:26:36

Report to Moderator

Re: O/T alternator or battery?? in reply to old, 10-21-2007 10:03:52

some people claim their batterys last 8 yrs. or more. How come I never have that luck?

[Log in to Reply] [No Email]

old

10-21-2007 21:44:19

Report to Moderator

Re: O/T alternator or battery?? in reply to flying belgian, 10-21-2007 19:26:36

Only battery I have had that lasted that long was never used for 9 of those years and kept in a heated room LOL

[Log in to Reply] [No Email]

hay

10-21-2007 06:27:40

Report to Moderator

Re: O/T alternator or battery?? in reply to old, 10-20-2007 21:08:24

voltage should be about 14.2-14.4 at fast idle startup when cold in the morning. a bit less on a hot engine. make sure the battery terminals are clean and tight. the ones on my 1996 chevy keep getting loose and the gauge shows when they need tightening. must be the connection on the side terminal battery.

[Log in to Reply] [No Email]

Allan In NE

10-21-2007 06:33:20

Report to Moderator

Re: O/T alternator or battery?? in reply to hay, 10-21-2007 06:27:40

The Chevy boys have a "fix" for that.

A little lead, square-shouldered spacer washer at the battery connectors.

Had to have my wife's car given the treatment. It always acted up at just the wrong time. :>(

Allan

[Log in to Reply] [No Email]

Allan In NE

10-21-2007 06:20:15

Report to Moderator

Re: O/T alternator or battery?? in reply to old, 10-20-2007 21:08:24

Set of battery cables cured mine about a month ago. Had the same identical symptoms as you're talking about.

I've also gotta run a new feed wire from the temp sender to the guage due to high resistance (old). Darned thing has been reading "half" of normal for 20 years now.

Someday, I'm gonna get around to doing that job. :>)

Allan

[Log in to Reply] [No Email]

El Toro

10-21-2007 06:02:37

Report to Moderator

Re: O/T alternator or battery?? in reply to old, 10-20-2007 21:08:24

You should be seeing 14 to 14.5 volts at your battery terminals with the engine running above a fast idle. I would have your local shop to check the alternator. Hal

[Log in to Reply] [No Email]

john in la

10-21-2007 05:36:30

Report to Moderator

Re: O/T alternator or battery?? in reply to old, 10-20-2007 21:08:24

A battery is only a store house for power. If you can come back 24 hrs later and the truck starts the battery is most likely good. Since you have MUCH more power going out the cables to crank the motor than you have going in when charging; I would say your cables are good.
So I would think you have a alternator problem. Most likely a diode gone bad.

[Log in to Reply] [No Email]

MarkB_MI

10-21-2007 05:12:17

Report to Moderator

Re: O/T alternator or battery?? in reply to old, 10-20-2007 21:08:24

Sounds like you've got a blown diode. There are six diodes in your alternator and it only takes two good ones for it to put something out. (The alternator is three-phase, one pair of diodes rectify each phase.

Also, I believe your alternator has a "diode trio" that operates the idiot light; that can go bad too. If it does, and you have an idiot light, the idiot light will glow faintly.

[Log in to Reply] [No Email]

T_Bone

10-20-2007 22:19:20

Report to Moderator

Re: O/T alternator or battery?? in reply to old, 10-20-2007 21:08:24

Hi Rich,

Any alternator should put out 13.5v at idle rpm. Since you cleaned the cables, tried jumper wire?, and tighten the belts, sounds like a free testing would be next at a chain store.

T_Bone

[Log in to Reply] [No Email]

Old Ford Mechanic

10-20-2007 22:11:24

Report to Moderator

Re: O/T alternator or battery?? in reply to old, 10-20-2007 21:08:24

Old,Could be the bridge rectifier letting go.

[Log in to Reply] [No Email]

Walt Davies

10-20-2007 21:49:31

Report to Moderator

Re: O/T alternator or battery?? in reply to old, 10-20-2007 21:08:24

Alternator output should read 13.8 volts.
Walt

[Log in to Reply] [No Email]

old

10-20-2007 21:53:26

Report to Moderator

Re: O/T alternator or battery?? in reply to Walt Davies, 10-20-2007 21:49:31

It does if I rev the engine up but if idle it reads around 12 volts

[Log in to Reply] [No Email]

Bob

10-20-2007 21:19:33

Report to Moderator

Re: O/T alternator or battery?? in reply to old, 10-20-2007 21:08:24

Did you check the belt and pullies? A slipping belt can cause that.

[Log in to Reply] [No Email]

old

10-20-2007 21:40:09

Report to Moderator

Re: O/T alternator or battery?? in reply to Bob, 10-20-2007 21:19:33

Belts good and tight, so I know thats not the problem. Thats the first thing I checked because I figure that might be the problem and its not. Guess it could also be a bad battery cable also. Funny thing is it starts up just fine but the gauge doesn't read as it did a couple weeks ago

Hobby farm

[Log in to Reply] [No Email]

36 coupe

10-24-2007 03:43:34

Report to Moderator

Re: O/T alternator or battery?? in reply to old, 10-20-2007 21:40:09

Paid 89 cents for my last hydrometer.Ony way to catch tired batteries.Uneven cell readings mean trouble.

[Log in to Reply] [No Email]

GeneMO

10-21-2007 04:00:12

Report to Moderator

Re: O/T alternator or battery?? in reply to old, 10-20-2007 21:40:09

Hey Rich how you doing? Hey if it works dont screw with it. That's my motto.

See you, Gene

[Log in to Reply] [No Email]

[Options] [Printer Friendly] [Posting Help] [Return to Forum] [Log in to Reply]

TRACTOR PARTS	TRACTOR MANUALS

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today. [ About Us ]

Home | Forums

Copyright © 1997-2023 Yesterday's Tractor Co.
All Rights Reserved. Reproduction of any part of this website, including design and content, without written permission is strictly prohibited. Trade Marks and Trade Names contained and used in this Website are those of others, and are used in this Website in a descriptive sense to refer to the products of others. Use of this Web site constitutes acceptance of our User Agreement and Privacy Policy

TRADEMARK DISCLAIMER: Tradenames and Trademarks referred to within Yesterday's Tractor Co. products and within the Yesterday's Tractor Co. websites are the property of their respective trademark holders. None of these trademark holders are affiliated with Yesterday's Tractor Co., our products, or our website nor are we sponsored by them. John Deere and its logos are the registered trademarks of the John Deere Corporation. Agco, Agco Allis, White, Massey Ferguson and their logos are the registered trademarks of AGCO Corporation. Case, Case-IH, Farmall, International Harvester, New Holland and their logos are registered trademarks of CNH Global N.V.

Yesterday's Tractors - Antique Tractor Headquarters

Website Accessibility Policy