Can I repair my alternator?

lustika · Aug 27, 2008

Hi!
As a new member it feels good to read about all yanmar owners out there i the big world. Perhaps some of you can help me out. My alternator on my ym 1502d is just charging 11.8 volts when I test it on the battery. What could be the problem? I have tried to clean all the connecting parts and now I think my alternator/generator is broken. Is it possible to repair or do I have to buy a new one? I use my tractor allmost every day and it takes a while to get spareparts from US to Sweden so I would be very happy if someone has got an idea.
By the way I hope you can understand my swedish english.

/ Anders

J_J · Aug 27, 2008

If you can't find parts for it, you can replace it with a one wire Ford alternater which has more amps. You can find them on Ebay, or local.

E Tractor · Aug 28, 2008

I had this problem with a ym2000. Look for a local starter/alternator shop in your area that rebuilds and checks them. Napa and AutoZone had no clue on how to check mine and said it was bad. Turned out it was ok just the regulator was bad. I bet your alternator is ok just the regulator but I could be wrong. Any way it was on only $40 to rebuild my alternator so I went ahead and had it done as the bearings were a little noisy.
good luck
Erick

lustika · Aug 29, 2008

Thank you Erick!

I will try that! Going to take the regulator to a shop this weekend so we will see if you were right.
By the way! I like your buses. I have had one myself and it is still the best car I have ever had.

/ Anders

E Tractor · Aug 29, 2008

thanks for the complment on the buses. Wish i had more time to play with them, between house, kids, 13 ft whaler, busses, all the other stuff I need to do and of course the yanmars I am spread too thin!
later
Erick

choffman41 · Aug 30, 2008

Depending on what kind of system you have, you may have an alternator that puts AC out to the regulator. Try unplugging the connector to the alternator and check the voltage there to see if it's putting out. If it is an AC type, you should get about 20VAC across the 2 terminals (at operating RPM).
If so, you can assume the regulator is bad (usually the case).

J_J · Aug 31, 2008

I am thinking that 28.4v AC would be more correct for this reason. That rectifier assembly is a full wave bridge, and rectifies the 28-30v AC voltage to one half which would be around 14.2 DC. The AC voltage has to be above 24v AC in order to rectify the proper voltage for charging a battery. In the external regulator assembly, there is a circuit, using a zener diode or a newer component to control the charging. In a one wire alternator, the rectification and regulation is done in the alternator, and if you can spin that alternator, you should get voltage if 12 v is applied to the ig terminal for field. In a permanent magnet alternator the alternator is self igniting.

You can even check the diodes for a front to back ratio of 10 to 1 using an ohm meter, and replace them if bad. You need to reverse the leads on the ohm meter to make this check. Some of the newer meters have a diode checker.

lustika · Sep 1, 2008

Hi!

Thanks for all good advices. Now i am sure that it is my regulator that is broken. Off course i can have one shipped from the states but i would prefer to buy one here in sweden. Can i replace the original with another one? I have found regulators from 100 swedish crowns wich is about 15 dollars but i dont know if they works. They are for bosch generators. I also know were to find cheap regulators to a snowmobile. How much is going in the regulator and how much should go out would be the important thing to know, or???

I think it is allmost impossible to find some one here in Sundsvall that knows enough about this things. Many knows a lot about a lot of things but no one knows anything about yanmars and all regulators are sold by big warehouses and they dont know ****. The world is upside down!!!!!

/ Anders

sandman2234 · Sep 1, 2008

I am sure somebody around you knows about it, as electricity generating from an AC source isn't a new science. Just have to find the right ole geezer sitting on his porch and get him to start talking...
David from jax

Mickey_Fx · Sep 2, 2008

As I've mentioned before recently, the electrical system is not unlike the electrical system one finds on small engines found in LT and GT's. Permanent magnet alt outputting AC running into a voltage reg that rectifies the AC and controls the voltage. Ya might find one of these VR's on an engine spec'd with a 15-20A charging system.

Another source for the Yanmar reg is as close as JD. Yanmar made/makes a number of smaller tractors or at least engines for JD. My son's JD 455 has a Yanmar engine the the alt looks just like the one on my Yanmar.

Since this is such a common problem with many Yanmars, if it were me, I'd be looking at swaping out the alt and reg to a small model found on a common car.