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alternator going bad?

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15K views 16 replies 6 participants last post by  13982  
#1 ·
so yesterday the battery went dead in the 4510. no dash lights or anything. i thought it was just a bad battery so about ten minutes ago i replaced it. after replacing, i started it up and, viola! it works:yahoo:started right up! i drove it around a little, and then parked. about 5 mins. ago, i tried to start again.

nope. nothing. not even enough juice to lift the fuel gauge. so, is it a bad alternator? and if so, is a common part or yanmar specific? or is it some weird thing the dealer will have to fix?

thanks!!
 
#2 ·
You'll need a volt meter to diagnose the charging system correctly. A bad battery can display similar symptoms to a bad alternator. Test the battery voltage with the tractor running, you should see 13-15 volts. If you don't, then test the voltage at the alternator. Same expected results, if you're not getting anything then it's a bad alternator. Make sure the belt is tight before testing.
 
#3 ·
thats the problem. it wont start up or run. i can hear the fuel valve open and then close when i turn the key on.
 
#4 ·
If it won't turn over at all, test the battery first. Check voltage at rest, then voltage while trying to start. If you get less than 8-9 volts while trying to crank you have a bad battery. A failed alternator can damage the battery, and a failed battery can damage an alternator. Can you jump start it for diagnostic purposes? The alternator has nothing to do with the starting system, if it won't turn over you need to charge or replace the battery. Can't say which without knowing what the loaded voltage is.
 
#5 ·
hmmm. i just replaced the battery with a brand new Exide brand battery. would hate to think it was bad from the start.
 
#9 ·
so charged up the battery on the trickle charger for a wile. volts across the terminals was 12.91. i turned the key and- voltage dropped to 2.09vdc.
 
#11 ·
what else could it be?
 
#12 ·
What else could what be? Your description; new battery started the tractor once then wouldn't turn over, then dropped from 12-2 volts points firmly to a failed battery. Until we test the voltage at the battery with the tractor inning, we don't know if it's charging or not.

If it isn't charging, the alternator could be bad or you could have a within problem. That's why we want to test charging voltage at the battery first, then at the alternator itself if it isn't charging at the battery.
 
#13 ·
my uncle recommended cleaning the ground connections. so i did. now it works better, but i have to have the charger connected when i try to start.

now, for the ???? thats been nagging me. what caused this battery to go bad?
 
#15 ·
As I said, seems like lately I've seen 1-2 batteries a year junk out of the box. Don't know exactly why, but there are a number of possibilities. Shipping damage could crack a lead plate inside enough that it won't support the required current flow, or they could sit in a warehouse for an extended period and be left dead. Never bothered to dig into it.

In my experience, any battery dropping 10 volts; especially just from turning the key on, is garbage. You may clean a few connections and trickle charge it for a few days and get it to turn over, but to what end? There is something wrong inside the battery and while you may nurse it back to health now how much has the overall lifespan been shortened? It's under warranty, if it was mine or one my my customers' I would replace it and have the new battery tested before you leave the store. No reason to risk it.