thinking bad alternator - thoughts?

[1996ezrider]

Battery is at 12.5V. When cart is running full, volts does not rise. Is there other testing I should do? Thanks in advance.....

Ezrider

[Heliarc]

I'm assuming you tested it with a voltmeter at the battery terminals while the engine was running.If it holds 12.5 it should be ok to go though that is a low reading.It should be up around 15 volts when it's running.You might have to get it up on stands and run it with the back wheels up to get a good reading on it.The way mine is wired, it will idle without holding the pedal.At idle it only puts out about 12 volts.When the engine is at speed though the reading climbs to about 15 volts.

One test you could do is disconnect a battery terminal while the engine is running.However I'm not sure about what it may do to other components on the cart.I test car alternators this way.If the engine dies when the battery terminal is disconnected, then you aren't charging.However, jacking it up, and getting the engine to speed, the testing with a voltmeter at the battery terminals should be a good enough, and safer test.

Another test would be to remove your alternator and take it to an auto parts shop.Most shops can bench test your alternator.If your alternator checks out ok, you can look at your connections, and your regulator.They might be able to test that as well.

Now, what could be wrong.This could actually be a few things.You could have some corrosion buildup on your battery terminals.This will prevent it from charging the battery.It would crank slow as well since the battery isn't getting much of a charge, or it might not crank at all unless you jump start it.But once started it would probably run fine.

A bad voltage regulator will prevent you from charging as well and will make it seem like your alternator is dead.This is a much cheaper fix than an alternator.

Hope this helps.If not, put up what kind of cart you're working with and the symptoms you experience.This shouldn't be a terrible issue to solve.

[1996ezrider]

The 12.5 volts holdingsteady was with cart jacked at high speeds. Is the next step a bench alternator test? Terminals are all good.....thanks in advance!

[pachanga90]

Don't unhook the cables while its' running,it can damage the electronics,this goes for cars/trucks too.Test the battery voltage,then start the cart and recheck.If no change,its' not charging.12.5 is battery-voltage on a good battery,you should see at least 13v with a max of 14-14.5v.With it running,the voltage should climb a little at idle,and more with RPM-Increase.Check over all your connections,take them all apart from the battery,thru the whole system.Clean all grounds too.One dirty connection can shut it down.If nothing changes at this point,pull the generator and take it to a rebuilder to be tested,bring the regulator as well.Hope this helps.

[Heliarc]

Originally Posted by pachanga90

Don't unhook the cables while its' running,it can damage the electronics,this goes for cars/trucks too.

Yea, I know it isn't good for it.Makes the voltage regulator see a dead battery and start putting out full tilt.The vehicles I've done this on were my own.I've never had anything burn out, but that was probably luck.I've only really done it before I possessed a voltmeter back in the day.

[COURTESYCART]

check the green wire going to the starter/generator. they are known to break off, this makes the generator go into charge mode.

if that is ok, more than likely you have a bad regulator.

NEVER DISCONNECT THE BATTERY WHILE RUNNING.

Heliarc. DO that to a newer truck/car and see how expensive it will be to fix. ECU's dont like power surges. Most of the new cars will completely shut down if batt volts is lost anyway as a safe mode, so this is NOT a good test. I am a ASE master certified tech, BMW master Certified tech and a Certified Mercedes tech. Doing this to a german car can/will cost you a (as in 1) 1500.00 ECU.

[pachanga90]

The same goes for anything with an engine these days.Electronics,including CDI-Boxes,Do Not Like Surges.I'm ASE Master-Certified in Diesel/Heavy-Truck myself,I was taught very early on,when computers started in cars/trucks that pulling the cables = trouble.

[Heliarc]

Originally Posted by COURTESYCART

Heliarc. DO that to a newer truck/car and see how expensive it will be to fix. ECU's dont like power surges. Most of the new cars will completely shut down if batt volts is lost anyway as a safe mode, so this is NOT a good test. I am a ASE master certified tech, BMW master Certified tech and a Certified Mercedes tech. Doing this to a german car can/will cost you a (as in 1) 1500.00 ECU.

That's the thing.I don't have a single vehicle with an ECU.I like to work on my cars myself, not have to take them to a computer programmer.And, as I said before, I did this a couple times back in the day before I had a voltmeter and I know it can be destructive, so can we please lay off it now?

[pachanga90]

Heliarc,Just trying to prevent damages,even on the carts,electronics are on everything with an engine since the early 80s',so just giving a helpful warning.My Dad has damaged enough stuff trying to test it like he did in the 60's/70's.He finally listened after it cost him a CDI-Box.Nothing personal,don't take it that way,just trying to help.

[Heliarc]

No problems, I just wanted to let you guys know that I know it isn't really a good idea and end the subject.Looking back though, I guess I shouldn't have even mentioned it.I know even on older motorcycles it can burn out your voltage rectifier.So let's just consider that part retracted.