Super A Problem Starting

Battery shows 12 volts. Alternator is charging battery. Won't start unless I jump it. Idiot light glows then goes out after tractor runs a while. Any thoughts?

Bad connection somewhere.

Id start by removing, cleaning and wire brushing bright n shiny, each and every battery, cable, starter, switch and ground cable as there may well be a bad resistive corroded or loose (IE voltage dropping) connection.

If the ground cable is attached to some thin or rusty sheet metal run it instead to a good clean frame ground bolt on or near the starter.

If alllllllllll cables n connections are good there could be a faulty resistive starter switch or starter solenoid, maybe try to jump around it n see what happens. Tractors that have that saddle mount on starter motor push switch are known to develop burned pitted resistive carboned contacts and tractors that use solenoids can develop the same burned pitted carboned contacts also.

Of course, starter motors can go bad if all the above checks out okay. When you try to start her do the lights dim way down and voltage drop drastically??? If so the starter motor or starter drive (Bendix if so equipped) can be at fault. If the lights don't dim and voltage dont drop too much then id lok for a bad resistive connection

HAVE THE BATTERY LOAD TESTED it may be at fault???????????

John T

What does battery show while cranking?

If the battery show 12 volts nothing more it is not fully charged. A full charged battery will read 12.50 plus. So charge it and or have it load tested. Plus clean all battery cable connections. Also battery cable do go bad and you cannot see that and many times even an ohm meter will not show that they are bad. Or the starter it self maybe going bad so the extra amps from a jump makes it work

Back to my point, 12V sitting or 12V cranking?

Big difference.

i have a used 6 volt battery, that has reversed polarity. any fix for it? or can i run it by changing cables?

If a battery got incorrectly charged at the wrong polarity I usually use a light to discharge it total then try a correct polarity recharge.

John T

Rich, actually a full charged flooded lead acid battery stabilized at rest at 77 Degrees will be 12.63 volts NOT 12.5+

FYI here is a chart of battery voltage versus state of charge at 77 Degrees


100% charge, Unloaded Voltage = 12.63 volts
75% charge, Unloaded Voltage = 12.30 volts
50% charge, Unloaded Voltage = 12.00 volts

OF COURSE if your meter is a cheapie or isn't very accurate it may or may not reflect accurate voltage WELL DUH lol

I hope this helps

Best wishes and God Bless, take care now

John T

12.5 plus is a correct reading taking in to account most people have the cheap VOM's that are not calibrated so I use the 12.5 + to account for the many different reading one can get when you compare say 10 meters to each other. You do not take into account that a cheap meter is only going to give a ball park reading

EXACTLY JUST AS I INDICATED Glad you agree with me Rich regarding possible inferior and inaccurate grrrrrrr meters.

As I said if you have a cheapie or an inaccurate meter you may or may not get the right voltage readings. Some may read HIGH
like 13 volts, some may read 12.5+ as yours, while others may read LOW down to 12 or so !!!!!!

HOWEVER so you and others will have the CORRECT information just in case you have a decent quality meter

A FULL CHARGED LEAD ACID BATTERY AT REST AT 77 DEGREES IS 12.63 VOLTS (NOT 12.5 like an inaccurate meter indicates)

Hope this helps you and others, sounds like your meter reads LOWWWWWWWWWW (12.5 instead of actual 12.63) but I own and
have owned plenty of those myself lol My old antique Analog Simpson shows 12.6 for a full charged battery, I bet its still
more accurate then a new cheap Harbor Freight

God Bless

John T

I own 3 meters. One I got form HF 20 plus years ago. One I got in a box at an auction and the newest is one from TSC and I payed $5.95 for it. I can use all three and all three give a different reading on the same resister or battery but all come into the 12.5 give or take a few hundredth as in one may read 12.5 and the other 12.59 and the analog one well that depends on how your looking at it as to what you see or is yo have your glasses on. I guess one of these days I need to see if this navy surplus O-scope works and then see what type of reading it gives on things

thanks

Sounds like me. I lost count of how many I have laying around. Still I prefer my old trusty Simpson 260 Ive had over 40 years it seems. Usually most of my meters (on a charged battery) read pretty darn close to 12.6 WHICH IS THE ACTUAL VOLTAGE OF A FULL CHARGED 12 VOLT BATTERY.. I had one old one that read like 12.8 but not many of mine read low like yours. Of course if the battery you were testing WAS NOT FULL CHARGED then that reading of 12.5 you get MAY BE CORRECT AFTER ALL. Heck if the battery was discharged maybe 10% or a tad more that meter of yours which only reads 12.5 MAY BE DEAD ON lol

A 6 volt battery would only be 1/2 and if full charged would be 6.3 volts, while the 12 is twice that or 12.6 volts full charged. The reason being a 12 volt is made up of six cells in series each of which are 2.1 volts and 6 x 2.1 = 12.6

So I guess all I can do is advise the gents of what the true voltages are, but warn them if they have an inaccurate meter no tellin what it may register, maybe 12 to 12.5 to 13 lol

Take care now. Hope this helps

John T