troubleshooting charging system

coloradotrout · Nov 8, 2005

Strange indeed. My clamp-on HF meter only as 1v dc accuracy - no decimal accuracy, so I pulled out my 30 year old Radio Shack analog tester. I'm in a range where the reading is about middle of the meter. Battery was 11v, rect/reg was 13v. When I switch to AC volts there is AC on the line. Is this normal? Even though it's suppose to be a DC circuit. Frustrating.

I put the covers all back on last eve. The rect/reg is under the steering column on the RH side. I still want to take a measurement from the pos term of the batter to the frame ground.

Soundguy · Nov 8, 2005

( Looks like my 2004 BX23 is still using a non std & "crude" type of charging system )

Crude may have been a hard term.. perhaps.. 'less sophisticated' is a better term.

I much prefer variable field control regulation, as well as over current control.

( but that the rectifier is built into the outboard regulator too!
)

I've seen that on grey market japanese units.

Soundguy

Soundguy · Nov 8, 2005

( How can 13v at one point diminish to 11v at another? )

Voltage drop.. either a restive contact, restive short.. or resistance due to wire gauge restriction.. like a pinched wire barely making contact.

Soundguy

Soundguy · Nov 8, 2005

( Battery was 11v, rect/reg was 13v. When I switch to AC volts there is AC on the line. Is this normal? Even though it's suppose to be a DC circuit. Frustrating )

Makes perfect sense. the charge out line has 13v on it. that battery only has 11v.. that means there is a break in the wire... The 'ac' you are reading onthe 13v line is probably just 'choppy' dc. If you have ever seen unfiltered half or even full wave dc on a scope.. you will notice that it is just the positive portion of a waveform... some meters read that 0 to + pulse as ac, when normally it would be a neg to pos swing, passing neutral. This is the same reason why most cheap vom's aren't real usefull for measuring dc generator output at the armature of an old gen, with no battery attached to filter the output.. the brush 'noise' confuses the meter.

I'd trace that line where it goes from 13v to 11v.. and that is where your problem is. ( Fuse? )

Soundguy

coloradotrout · Nov 9, 2005

not much in that path.. reg/rect (13v) to fuse (although that parallels off to the switch also) to starter to battery pos term. I should be able to measure Vs at that fuse, and starter fairly easily. Course I say that sitting at my desk. Seems I find a different story once I pop the covers..

But what is confusing.. is that circuit works both ways. With the engine off, it's still "live". The battery itself drives 11v to that reg/rect. That's why a short, etc seems unlikely.

At that parallel off to the switch there is a whole other set of circuitry. When running, that activates a relay, and presents the voltage to another lead on the reg/rect. I'd probably have to copy this schematic and post it to make any sense. And I suppose there a other points of failure also, as presumably this is only the "charging schematic" and other electrical circuits could have an impact.

coloradotrout · Nov 10, 2005

still a big mystery..

battery was dead again, so I put it on the charger, and measured current to the battery while on the charger.. started at about 9A and slowly went to 2A.. just as a charger is suppose to work.

So I start the engine and measure the current on the pos. terminal wire. It varies w/ engine rpm, from about 4A to 10A. If I unplug the alternator, that current goes to 0A. Makes sense right? Alternator running.. current flowing. Alternator off, no current.

Next I put test leads into the alternator path and measured voltge. This is AC out. When the alternator is in the circuit there is about 15V AC across the 2 alternator leads. When the alternator is OUT of the circuit there is up to 50V at high rpm. Still kinda makes sense to me.

The only bizarre scenario I an dream up is the battery is delivering current to the alternator!! A reverse of what should happen! That would explain the current readings. But it seems crazy. Or maybe I just have a bad battery?

Volfandt · Nov 11, 2005

It appears that something is draining your battery down. I don't recall if I explained a simple test procedure in an earlier reply so I'll repeat it if I did.

Charge the battery back up and reinstall it into the tractor if you removed it to charge. Connect the negative (neg) battery lead up but not the positive(pos) lead.

Get a 1056 or 1156 auto lamp and solder a lead to the lead tip and another to the brass/copper base. Wrap one of these leads around the pos battery term and use a pr of vise grips to hold it there. Wrap the other lead around the tractors pos battery cable clamp. Basically you have series'd in the lamp between the battery & the tractor.
With the switch off the lamp should NOT glow. A faint to bright glow indicates that something in the tractors electrical circuit is grounded. To isolate pull fuses one at a time and/or start disconnecting device connectors one at a time. When the lamp goes out you've found the problem.
Those reverse current diodes are generally the 1st to suspect but I've seen oil pressure switches do it also. Anything that had battery voltage sitting on one side with the key off can be suspect.

If you have no glowing lamp, turn the ign switch on to verify that it will glow.
If the lamp test good and it doesn't glow then hook the pos battery lead back up and series in the lamp to teh neg lead. If no glow then the system isn;t pulling enough amps to pull the battery down overnight.
You can use an ammeter set to milli-amps in the same manner but chargeing circuit will always draw a very slight current draw and this can be misleading.

Good luck
Volfandt

coloradotrout · Nov 11, 2005

Sounds easy enough to test.. but the drain would be pretty small. When I put a good charge on the battery it will last several weeks.. or probably 50+ starts. I may actually tap into the pos. term at the starter.. would prolly do it good to disconnect, polish, and reconnect. It's a short run of wire.. 2 ft maybe.

Soundguy · Nov 13, 2005

( The only bizarre scenario I an dream up is the battery is delivering current to the alternator!! A reverse of what should happen! That would explain the current readings. But it seems crazy. Or maybe I just have a bad battery? )

I'd go with bad battery.. or short. It was a good guess.. but you are a little rusty on current theory. First.. if you had a vom, you should know which direction current was flowing.. next.. current flows from the source that is a higher voltage potential to a location of lower voltage potential. in other words.. your 14v alternator 'sends' current' to your 12v battery... Current will not travel from an area of low potential to an area of high potential.. that's an oversimplified explanation.. but pretty much holds water.

2 tests.. first.. remove battery terminals from battery.. and attach vom with test clips.. set to voltage.. check the meter... remove clips and check battery every time you walk by.. let battery set same length of time that it would take to go dead int he tractor. if the battery is internally discharging.. it will do it and you can measure that as a voltage drop... if it is the battery.. replace it.

next ...Get a test lamp or low wattage bulb.. remove your neg battery post and gator clip that lamp inline with post and terminal. if the lamp lights a bit.. then you have current flow.. and thus a short. Now.. start at the alternator and start disconnecting wires one by one working back toward the dash ./ battery.. when you finally pull a wire that make sthe lamp go out.. that circuit is the short..

Soundguy

djg · Nov 13, 2005

Soundguy is right. I troubleshot a car system years years ago by using a light bulb in series with the battery, and found a bad relay causing a current drain. I would not have ever suspected this part as the culprit. If there is no current drain, battery is bad.