40c question

kevencyr · Post by **kevencyr** » Sat Apr 23, 2016 4:17 am

just put a new alternator, would like to check if it charging. if i do it like old car by removing the positive on the battery, should my engine keep turning? cause right now, when i remove the positive, my engine shut down. thanks

Stan Disbrow · Post by **Stan Disbrow** » Sat Apr 23, 2016 4:59 am

Hi,

I presume you have a 12v conversion. There are 6v alternators out there, but they are not common.

Alternators don't keep working when the battery is disconnected. They need battery power to form the field as they don't have magnetized iron plates they way generators do.

To check charging, use a voltmeter on the battery to look for a voltage of around 14 volts when the machine is running.

Stan

Paul J · Post by **Paul J** » Sat Apr 23, 2016 7:39 am

I've noticed that there is a slight amount of magnetism in the area of the back bearing on a working alternator - barely noticeable, but enough to swing a screwdriver if held lightly. As Stan says - a meter is the best proof, but I'm apt to have a screwdriver in my pocket, not so apt to have a meter.

kevencyr · Post by **kevencyr** » Sat Apr 23, 2016 8:34 am

yes it a 12 volts, got got a new alternator 85amp. for some reason my meter gauge on my dozer blowup. so i was wandering if the alternator was still charging. also notice a wire that was really hot, so made it bigger. hope everything is fine.

Stan Disbrow · Post by **Stan Disbrow** » Sat Apr 23, 2016 2:09 pm

Hi,

If it was the wire from the alt to the batt, and the old alt was lower output, then I can see it getting warm with 85 amps available.

Any other wire gets hot, just upping the gauge is asking for smoke to be let out of something else......

The best troubleshooting item for any electrical work is a DVM. And, I always suggest Fluke meters. Get a good one, not a cheap one.

Stan

kevencyr · Post by **kevencyr** » Sat Apr 23, 2016 2:24 pm

great news, found the problem. had a wire that was shorting on the frame, fixed all wires and running great, did a voltage test and charging. thanks guys.

jtrichard · Post by **jtrichard** » Sat Apr 23, 2016 2:35 pm

Hey Stan you being the electrical Guru how do know IF you have a queer AMP?

egeor · Post by **egeor** » Sat Apr 23, 2016 3:28 pm

Stan If the alternator stops working with out a battery,How would a car run without a battery. On more than one occasion I have used a battery to start a car than removed the battery . One time i drove 3 miles to an autoparts store with out a battery. that vehicle was a 95 VW definitely an alternator.

thanks

jtrichard · Post by **jtrichard** » Sat Apr 23, 2016 5:07 pm

I know one thing that can happen with NO battery they CAN run BUT there is NO voltage control ( volts can go sky high) so you can fry anything (ON) that is voltage sensitive

Stan Disbrow · Post by **Stan Disbrow** » Sat Apr 23, 2016 5:56 pm

Hi,

I have always had cars and trucks sputter and then die if the batt became disconnected while running. The regulator can't work right, so the voltage swings ever lower and higher until the low goes to zero and the thing quits.

The only thing that might help is if you had a big capacitor somewhere, like for an audio power amp.

And, as noted, the high side excursions love to fry all sorts of other things which are turned on at the time.

My neighbor's son just had his the battery in his modern VW go bad while running, and it fried his PCM and rather costly audio system. So, I guess the big cap in power amp didn't help.....

Stan

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