troubleshooting charging system

[coloradotrout]

Continuing saga.. I tested both diodes, they appear to be OK. I hear a relay click when the switch is ON. I tested AC voltage from alternator at the regulator/rectifier. It's same as at the alternator, 20v-50v. While running I measured about 25A AC current. Fuses and diodes appear to be OK, but I'm not getting >12v DC when running. I checked various point along the path and it looks OK. I really need to be able to plug the AC from the alternator into the rectifier and then measure the rectifiers DC out. To do that I'll need to splice in some wires so I can take the measurements. It's all one 6 wire connector. My best guess now is either 1) alternator is delivering good voltage, but not enough current or 2) the rectifier is not delivery sufficient DC voltage/current.

 

[Soundguy]

Rectifiers usual mode of failure is 'open'. in rare instances I have seen 'shorts'.. I have yet to see 'variable resistive' failures that deliver lower dc voltage from the rectified ac voltage.

Keep looking... You have ac source.. and no dc output...

How did you test the diodes? OOC?

Soundguy

 

[coloradotrout]

Re: diodes. I put a multimeter (ohms) across the 2 connectors. In one direction there is 10 ohms resistence (closed), in the other infinite (open). I also tested dc volts along the path to see that voltage was getting "past" the diodes. I'm pretty sure they are OK. In diode controls a relay, and that relay "clicks" with the switch on, therefore the diode must be working. I think it's either alternator or rectifier at this pt. If I can "splice into the rectifier connector" I can measure the dc output. That would be the next clue. After that it would have to be some kinda of current flow issue.

 

[Volfandt]

Typical rectifiers use 4 or more diodes which are wired in as a bridge rectifier. Many have one or two more diodes as reverse current limiters so the battery doesn't discharge back through the rectifier/alternator to ground. These could be the diodes you're reading, which appear to read good.

As for the regulator, most if not all solid state regulators utilize a zener diode & resistor to produce the reference voltage drop and in many cases an SCR to control current flow to the battery. There will be associated cap's, transistors and resisters to control these devces. And unfortunately they are generally sealed in epoxy makeing them unserviceable.

I doubt that low current flow from your alt is your problem. An alternator's produced current is dependant upon load. Since your not measureing any DC voltage output at the battery, theres no load applied....

I find it unusual that the rectifier isn't integral to the alternator as this has been the standard for years. There will have to be a minimum of 4 to 6 wires between the alt the reg/rect. Three leads for the stators AC delta wireing output. 1 or 2 Wires for the field input and at least one wire for a common neutral. Since you are getting AC voltage out then it's safe to assume that the 12vDC field voltage is getting from the reg/rect alternator hense the connection between the alt & reg/rect is good.
The reg/rect module will need at least two or three additional leads from the tractor. A 12vdc battery/power lead, frame/system ground and if you have an idiot lamp, a lead for it also. Thats 6 to 10 leads to the reg/rect.

Barring a blown fuse, or loose ground, it still sounds like a defective reg/rect. /forums/images/graemlins/grin.gif

Good Luck
Volfandt

 

[coloradotrout]

Thanks again for all the replies. Another update. There are 6 leads going into/out-of the rectifier/regulator. 2 lines in from alternator. 1 out to battery. 1 out to a safety relay that is diode protected to ensure current does not flow in reverse to reg/rect, 1 gnd, and 1 to a discharge light which indicates charging system failure. I made 6 test leads - connectors on both ends with exposed wire in the middle. I took measurements. In summary it looks NORMAL. Under load there is 15v AC across those alternator leads. Again, this is while plugged into the reg/rect and under load. Unplugged from rec/rect, there is 20-50v AC. The discharge circuit seems fine - nothing there to really care about anyway. With the switch ON, the rect/reg closes that circuit and the light comes on. Once running, it goes off. There is "battery voltage" on the lead to the battery, and with the switch on, there is "battery voltage" to the safety relay (indicating the relay is closed as it should be). I have a Harbor Freight multitester with the clamp on current loop. There is about 20-23 amps in the AC circuit to the rect/reg and (but not sure this multitest measures DC current) about 9-10 amps in the lead out to the battery.

All in all -- it SEEMS TO BE WORKING NOW! I see a slight voltage increase on that lead to the battery when the engine is running, about 12.5 to 13.5 volts. With engine off and key off, the battery voltage is just under 12v (I put it on the charger a night ago). But I do detect a slight increase in voltage (at the rect/reg) now that would seem to suggest I'm getting charging current.

It was pretty dusty in there.. the rect/reg was plugged full of dirt. I took the airhose to the whole area and cleaned it out. Also, I've disconnected and reconnected just about all the diodes, relays, connectors, etc that I can find (in hopes of clearing up any bad connections).

I did notice, this eve, with the switch ON, and engine not running, a relay clicking.. as if it was not making good contact. My guess, it's the saftety relay. So I pulled those connectors off and plugged then in/out several times. It's not clicking anymore. Perhaps that is the culprit. But I'm skeptical. I've left her "open" for now.. I'll take a few more readings when it's light out again.

 

[Soundguy]

</font><font color="blue" class="small">( I find it unusual that the rectifier isn't integral to the alternator as this has been the standard for years. There will have to be a minimum of 4 to 6 wires between the alt the reg/rect. Three leads for the stators AC delta wireing output. 1 or 2 Wires for the field )</font>

I've seen quite a few (strange and low tech ) alt's with permanent fields.. therefore no field control.. and output was very crudely regulated.. some yanmar dynamo are like this..

Soundguy

 

[Soundguy]

Sounds like you solved your problems,.. and it was a case of bad / dirty contacts..

Soundguy

 

[Volfandt]

In looking at the WSM for my BX23, it seems that the Dynamo not only has a permanent magnet field but that the rectifier is built into the outboard regulator too!
Looks like my 2004 BX23 is still using a non std & "crude" type of charging system /forums/images/graemlins/grin.gif
Theres two leads from the dynamo to the reg/rect and counting those two, 6 leads out of the reg/rect.
As long as it works /forums/images/graemlins/wink.gif /forums/images/graemlins/grin.gif

Glad the problem is fixed.

Volfandt

 

[coloradotrout]

I'm doubtful. I took some more measurements this eve. I do have 13+ volts on the output side of the reg/rect. But at the battery term, that voltage is 11. According to the schematic that lead goes to a fuse, then the starter, than the pos. terminal of the battery. How can 13v at one point diminish to 11v at another? With the switch OFF, there is 11v at the battery and at the reg/rect. Connectivity is therefore good. Hmm, but I just measured the Vs across the battery pos and neg terminal. I suppose I should have measured from battery pos to frame ground as that would be the same reference grn as the reg/rect. Another test to do..

 

[Volfandt]

Now that is strange /forums/images/graemlins/confused.gif

You should physically trace the battery to starter to reg/rect cable(s) out. At this point I would look for a skinned spot where it's grounding out or a spot where the cable is cut down to where just a few strands are makeing connection. There may be something spliced in that shouldn't be.

According to the schematic on my BX23, the chargeing output lead from the reg/rect goes a term on the starter solenoid and that is also where my battery pos term ties down. Yours sounds similar. Make sure you can't wiggle 'em around.

Check your meter also. Sometimes those range dials can give false readings if not in the proper range position.

Good luck
Volfandt