can alternator still work when light is permanently on

ivor from uk here and I could do with some advice concerning our Matbro Teleram 3 . the alternator light has been permanently on for some time but the forward/reverse and joystick controls all work ok .It has been starting alright up to recent cold weather ,the battery is at least 7 years old so I suppose I can't complain .I would like to know how do I check alternator output also some years ago I did some welding on the Matbro but I did not disconnect anything but there was no problem with light on
 
Can the alternator work with the light on?

Probably not, at least not to it's full potential.

When you turn the ignition on, before starting the engine, does the light come on?

If no, you may have a blown fuse to the instrument panel. The light should be fed hot from the ignition switch, the other side of the lamp is connected to the alternator. When all is working properly, the light gets fed power from each side, therefore the light goes off when the alternator is charging. However, with most alternators, the signal from the light is necessary to "excite" the alternator and get it started charging.

If the light comes on when the ignition is turned on, there is probably a problem with the alternator, as in a bad diode. If there is a bad diode, the alternator may charge, but not up to it's full potential. If your tractor doesn't have any accessories, or you never use them, it may be able to keep more charge going into the battery than is coming out to run the necessities.

You can check the alternator with a volt meter. With the engine RPM up off idle, check across the battery, should be around 14 vdc. If less, down around 12.5, or the voltage drops considerably when idling, or when a load is applied, like lights, there may be a problem. If there is no increase in voltage when running, it is not charging. Also be sure the belt is tight and not worn down to the bottom of the pulley.

If you suspect the alternator is bad, you can take it to the auto supply and have it checked, at least over here you can... If it is a common alternator, that can exchange it. If it is an alternator specific to the tractor, it may be better to take it to a rebuilder and have it repaired.
 
Well if you have a simple volt meter even a caveman could check it. Simply check battery voltage when it is not running and then check it when it is running. not running it should read 12.3 volts plus and running it should read 13-15 volts. Those lights area called idiot lights for a reason and well sorry but only an idiot depends on then telling you any thing. I have had more then one car that the idiot lights would stay on all the time but the charging system was check and double and triple checked and it was doing it job
 
Many auto parts stores will test it for free.

If you put a voltmeter on a good and fully charged flooded lead acid battery it should read around 12.6 volts subject to temperature (NOT 12.3 plus as posted below, that's a partially discharged battery) as it's made up of six cells in series each 2.1 volts and 6 x 2.1 = 12.6 volts.

Then start her up and at fast RPM a good working alternator should after some time raise a "good" batterys voltage to at least 13 and up to 14+ volts subject to battery state and RPM and voltage regulation circuitry. If it does that it must be charging.

If an idiot light stays on there could be a diode or a voltage regulation circuit problem assuming the battery itself is okay (like no dead or shorted cells).

John T
 
Almost every battery I EVER test give me a reading of 12.3 volts and always have. You need to think about the fact most cheap meters are not calibrated so if you get a 12.3-12.9 if it well with in any margin of error for the home shop guy testing a battery. I bet out of the 10 plus batteries I have on the place ALL of them will give me a 12.3 read give or take. That is what my meter always gives me on a good battery and it always has given me that so sorry John you need to think about what a person may have in a cheap meter and what it will really read not the text book calibrated reading that tyou will not get unless you spend the big $$ and do so every year to re-calibrate it
 
Sorry if you have an inaccurate meter Rich, hey don't feel bad, I've owned plenty of them and still do lol its nothing to be ashamed of.

I was ONLY correcting your "misinformation" that a battery should read 12.3 volts at rest (I had no idea how accurate or inaccurate your meter was, your post didn't state any such info, it just stated the INCORRECT 12.3 volt number) so others wouldn't get the wrong idea and think 12.3 volts represents a full charged 12 volt battery (actually its 25% discharged at 12.3 volts) WHEN THE CORRECT ANSWER IS 12.6 VOLTS IS FULL CHARGED subject of course to temperature since its comprised of 6 individual cells in series each of 2.1 volts and 6 x 2.1 = 12.6 NOT 12.3

For your and the others information here is a chart of the voltage versus percent of charge for a lead acid battery at 67 degrees

Temperature: 67 degrees Fahrenheit

Percent Hydrometer Unloaded
charge reading voltage
100 1.262 12.61
75 1.207 12.28
50 1.157 11.98
25 1.117 11.74
0 1.097 11.62


I hope this helps Rich, I'm here to help NOT argue but when I see misinformation I feel its best for all concerned to correct it rather then let it go by and hey, I've made a ton of mistakes and posted misinformation myself lol and am glad when it goes corrected so don't take it personal, I admire and respect all you do here to help others, keep up the good work. If you shop around there are a ton of good more accurate meters out there and they are not very expensive at all. I don't have any super accurate meters either grrrrrrrrrrrrrr lol but the ones I do have like my old trusty reliable analog Simpson 260 and RCA WV38A I believe and even my cheap digital meters show closer to 12.6 volts instead of the 12.3 you spoke of for a full charged battery at rest.

Best wishes hope you have a safe and happy new year, God Bless, glad to be of help.

John T
 
Sorry, the table/chart below didn't copy and paste correctly. Here it is again I hope lol it shows the unloaded voltage of a lead acid battery at rest, and at 67 degree F a full charged battery is 12.61 volts while 12.3 volts represents a 25% discharged battery.......

Temperature: 67 degrees Fahrenheit

Percent Charge Hydrometer Unloaded Voltage

100 1.262 12.61
75 1.207 12.28
50 1.157 11.98
25 1.117 11.74
0 1.097 11.62

John T
 
Sorry, the table/chart above didn't copy and paste correctly. Here it is again I hope lol it shows the unloaded voltage of a lead acid battery at rest, and at 67 degree F a full charged battery is 12.61 volts while 12.3 volts represents a 25% discharged battery.......

Temperature: 67 degrees Fahrenheit

Percent Charge Hydrometer Unloaded Voltage

100 1.262 12.61
75 1.207 12.28
50 1.157 11.98
25 1.117 11.74
0 1.097 11.62

John T
 
Being a lawyer you best go back and reread what I say. I say 12.3 plus so I am being 100% correct and I say it this way so as to cover the non-calibrated volt meters you buy form farm and home stores and other such places and all 3 of the ones I have on a good fully charged battery NEVER read over 12.5 tops and most of the time 12.3 or so. When I post I make sure to give a ball park figure so that way the person knows it can be a give or take a few 1/10s. Learned decades ago being a navy E.T. while it should read this or that, that any given VOM is not going to read the exact same as the next one and the measure of a battery no matter who what when or where is always a ball park reading and is not an exact science for the home shop guy
 
Whatever you say Rich, no use trying to correct someone who cant ever be wrong lol You're a good man and I know you mean well and try your best to help which I appreciate. PS you have my e mail, shoot me your mailing address and I will send you a better volt meter at no cost as a belated Christmas present. Also, if you have several older batteries that have been sitting around for extended periods they self discharge you know and perhaps they are 25% discharged which would read 12.3 volts SO MAYBE YOUR METER ISNT ALL THAT BAD AFTER ALL ????

Best wishes God Bless Rich and have a happy new year

John T
 
Well next time do not tell some one I am wrong when I know what I fine when I am checking a battery and it has been what I find over and over and over again. You need to think like a farmer not a Lawyer or Engineer and you know there is no such thing as a perfect reading on a cheap volt meter. 12.3 plus is close enough to the ball park to work for common testing
 
Sorry Rich I consider you a friend and a good man and try to remain polite and courteous to you and am trying my best to help and educate you NOT fight lol but you have to remain open to the chance RICH (like myself and all us mortals) COULD BE WRONG !!! there's no shame in that, I've been wrong a gazillion times lol

HOWEVER your statement

"not running it should read 12.3 volts plus and running it should read 13-15 volts"

IS JUST INCORRECT. NOTE I'm ONLY addressing your original post, not your later info about an inaccurate meter.

A much better sound engineering sound electrical statement is a good charged battery at rest unloaded at 67 degrees should read 12.6 volts NOTTTTTTTTTT the 12.3 you posted. ACTUALLY a reading of 12.3 represents a 25% DISCHARGED battery!!!!!!!!!!!

Of course, (A) if your voltmeter is NOT accurate as you discussed then the 12.3 may actually be 12.6 !!

(B) if your battery is a bit old or has set for an extended period, HECK IT MAY ACTUALLY BE 12.3 VOLTS AND
YOUR METER IS RIGHT ON..........

SO YOU MAY BE RIGHT RICH, IT MAY BE YOUR METER IS WRONG OR YOUR OLD BATTERIES ARE 25% DISCHARGED

Or maybe all the battery manufacturers since Edison are wrong and you're right???? Maybe you were correct when you posted

"not running it should read 12.3 volts plus and running it should read 13-15 volts"

Please DO NOT take offense or take it personal that I happen to agree with battery manufacturers instead of you and I still will go on record of stating " a good charged battery at rest unloaded at 67 degrees should read 12.6 volts NOTTTTTTTTTT 12.3 as you posted"

Hey Rich lets agree to disagree and remain friends trying to help one another, again I appreciate your help and know you try to help others and that's a good thing but I try to do the same and try to post the most accurate information I have.

May God Bless you my friend, Happy New Year and take care, I hope this helps

John T, Still your friend I trust. Heck if we all agreed all the time what a boring world lol
 
Your simply missing the point and it is very simple for field testing 12.3 is good enough for the common run of the mill farmer with a cheap meter. Ya if your in a lab testing high $$ stuff it is not good enough but when I say 12.3 plus I am correct for the run of the mill common man out in the filed trying to get his charging system back up and working. When I got out of electronics's I found that ball park on a tractor is more then good enough and to push it to the point of saying 12.3 in not good enough will make it so the guys reading here will think they have big problem because there meter reads something other then the 12.6 volts you say when in realities on the common cheap meter 12 plus is good enough for testing a battery to see if it is charged and 13-15 is good enough to know the charging system is working well enough for a tractor. Ya those number do not cut it in a Nuke sub that needs voltage to be exact but a tractor well it does not need exact numbers to work as it should.

Your over thinking things and in doing so can/will confuses people that do not have the back ground in electronics
 
WHATEVER you say I give up Rich, I tried to be professional, polite, respectful and courteous to help and educate
you why YOUR statement.........

"not running it should read 12.3 volts plus and running it should read 13-15 volts"


is INCORRECT (correct is 12.6 unless all battery manufacturers are wrong and 6 x 2.1 = 12.3 not 12.6)


but you're just unable to admit YOUR statement is inaccurate.


Best wishes, have a safe and Happy New Year and may God Bless you and your family

Your friend, John T
 

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