1990 Kubota B20 charging problem

[johneking]

I have a Kubota B20 that I have owned since 7/95 and now have a charging problem. I have removed the alternator and took it to the shop who said they know of no way to test it. The bearings feel solid and the guy said he has been told "if it's turning, it's producing electricity" and they don't fail. I have replaced the voltage regulator, cleaned connections etc. and still get a red no-charge light on the dash as well as no voltage increase at the battery after starting. Last year it did the same thing and I took all connections apart, cleaned them etc. and still no charging -- then one day the red no-charge light went out and it was charging again. Two weeks ago, it quit charging again!
Anyone have any ideas? Is there a way to test the alternator {it has two wires [both grey] coming out of it} or what do I do next?
Thanks.

 

[johnpawl]

What is the voltage at the alternater at idle and at 1500/2000 rpm?

 

[brain55]

That is a dynamo, it only puts out AC voltage, the regulator converts it to DC. It should be putting out a minimum of 20v AC, preferably closer to 30v AC.

Brian

 

[Soundguy]

i agree.. if it is a dynamo.. test right at the output to see if it is in fact making ac. if it is.. move to the rectifier/regulator pack.

nothing is infalable. just because something is turning doesn't means it will produce electricity forever.... things DO break...

 

[johneking]

There are two grey wires coming out of the alternator and I was told by the guy at the alternator shop there was no way to test it but you say it puts out AC current and I have been testing with DC.
I did get the charging problem fixed {the new regulator didn't do it and I am hoping the shop will take it back but doubt it as it is not a stock item AND is an electrical part} by replacing one of the 8 wires at the connector under the left side. One of the "grey" wires had burned the connectors and melted the plastic plug. After finding that and repairing it, the "no charg" light went out and I am seeing 14+ volts at the battery {not running I have 13v}.
If I choose to test the alternator, I assume I switch to DC and unplug both grey wires but don't know the procedure for positive/negative leads from the meter. If anyone can help with that, I would appreciate it.
Thanks for the replies,
John

 

[Soundguy]

If I choose to test the alternator, I assume I switch to DC and unplug both grey wires but don't know the procedure for positive/negative leads from the meter. If anyone can help with that, I would appreciate it.
Thanks for the replies,
John

DC? WHY DC when you've been told it is AC????!!!??

switch to AC.

and please don't unplug it. why be brutal to your equipment by unloading it.

slip the meter leads so that you can probe the plug/wires with it hooked up and loaded.

it's ac.. meter lead polarity won't matter.

ps. don't plug in 1 lead and touch the other lead. you might feel 30vac, depending on skin surface resistance.. sweat.. etc.

 

[DFB]

Sure a coil could have broken winding. Some spec ohm resistence across pin to pin and pin to ground

I had a similar problem with my John Deere recently. Cleaned the terminals good, double checked all the connections especially the grounds. My power feeds are wired across the starter. Even adjusted the belt tension. Tested relay switches. I finally replaced my battery and its all working ok now.

You can read alternator ac voltage output from the two leads either at the alternator or at the regulator connector. Read dc battery output coming from regulator harness conector too when its running. Do you know which wire is which? There are lots of diagrams on the web showing harness wirings for different regulators

 

[DFB]

Well I'm glad you got it fixed mine still screwed up just checked for voltage and its not charging once again. I get 50acv full throttle with alternator unplugged from harness reading only 17v plug back together found bad wires at connector too though...oh well back to the drawing board

 

[brain55]

The dynamo output voltage test is done with the two grey wires unplugged with the meter on AC there is no polarity to worry about it is AC voltage. It sounds like the problem has been resolved anyway.

Brian

 

[johneking]

OOOPS! Must have had a brain fart typing DC instead of AC -- sorry.
Not familiar with AC testing -- so to be clear, switch to AC on my tester, then probe one wire at a time with either the red or black probes into either of the grey wires coming from the alternator while running and still connected to the voltage regulator and I will get a reading of AC current?