DK40 Charging issue.

[bullebak]

Battery recently replaced.
Alternator recently replaced.
Belt tension correct.

NOTE: When the battery is not charging, the charge lamp on dashboard does not come on. Never did in the tractor's lifetime.

LAST SUNDAY:
Voltage on battery: 12.6V.

Normal start (ignition on), the charge lamp comes on and goes off when engine starts running. All normal. I measure the voltage on the battery, read about 13.5V (so I assume it's being charged). After a few hours work, park the tractor and was shocked to read just around 6V on the battery (while engine still running). On switch-off, battery recovers slowly.

I queried the alternator again, and for the umptieth time took it out and had it tested by the electrical company where i bought it from. They hooked it up to their testing setup and insist it's working normally.

I was told that one of the incoming connectors of the regulator should read about +10V, for the battery to charge. Fact is, it reads around 8.5V (approx) after starting.

This issue has been going on for some time and when I first replaced the alternator everything was ok for a few months. Any ideas?

All I can think of is perhaps a leak in the wiring or in one of the components but not enough to blow a fuse...

Circuit diagram attached.

 

[ritcheyvs]

For starters, make sure the glow plugs are shutting off and not draining the battery continuously.

 

[DieselBound]

I'd check all your wires (to/from alternator). Might have a bad wire and you're dropping voltage because of it. And in general, check your grounds.

 

[ritcheyvs]

...

LAST SUNDAY:
Voltage on battery: 12.6V.

Normal start (ignition on), the charge lamp comes on and goes off when engine starts running. All normal. I measure the voltage on the battery, read about 13.5V (so I assume it's being charged). After a few hours work, park the tractor and was shocked to read just around 6V on the battery (while engine still running). On switch-off, battery recovers slowly. ...

As I understand, after the engine has run for some time the battery voltage was down to 6v but the voltage rose after the engine as switched off. So there has to be be a large current drain through the key switch and the glow plugs are the only things I can see that could draw that much current without blowing the main fuse.

Why did you replace the battery and alternator? Does the battery charge properly with am external charger?

Maybe the alternator fails only after it runs for a time and gets hot from running at max output because of the glow plugs are always on?

 

[DieselBound]

Do these alternators have an on-board regulators? (I'd imagine so, but just thought I'd ask; if they don't, then check the regulator.) Of course, don't assume that a replacement alternator is fine. You pretty much have to go through and test everything.

 

[Hyrb]

This is either going to be something simple or require a lot of diagnostics. Simple would be a bad cell in the battery - yes, New batteries do have them. Or a voltage regulator or alternator that test good when cold and bad after heating up from running for hours. Had one once where expansion from heat caused failure but the **** thing tested great when it was cold...

Check your Grounds and Voltage Regulator. I am not Diesel savvy but have had similar issues on old cars where there was intermittent grounding causing the voltage to to vary at batteries and instruments. Also had intermittent shorts in a wiring harness that caused similar symptoms, insulation doesn't even have to be completely worn through to cause issue with wire to metal during vibrations.

Finding the bad spot where insulation has rubbed through on what seems like a mile of wiring harness is a true experience. If you have to start digging in try testing the voltage of each circuit through your fuse box.

 

[northcreek2624]

The glow plug thing makes the most sense to me. I'm thinking the pre-heat controller is bad, except that the glow plug light would be on all the time, unless it fried too.The ignition switch could also be the culprit. First though, make sure that the alternator belt is "tight". I worked in a repair shop in HS and many charge problems were as simple as a loose belt....Mike.

 

[pmsmechanic]

Subscribed

 

[ritcheyvs]

If you want to test the glow plug theory, warm up the engine for a few minutes, shut it off, disconnect the glow plugs, and then restart the engine. It should restart OK without glow if it's warm. If yours is like mine, there is a bus bar that connects the tops of all the blow plugs and the feed wire connects to the back end of the bus bar with a spade connector, which just slips off. Just ensure the disconnected wire cannot touch anything (maybe wrap the end in electrical tape).

You can also just measure the glow plug voltage several minutes after the glow light goes off. It should be zero. But the test described above will also prove if the glow plugs are or aren't draining the battery.

 

[bullebak]

Re: DK40 Charging issue.(Resolved)

RESOLVED

Thanks for all your input, guys. Much appreciated. However, it was none of the above.

Cause: Faulty ignition key switch (already a replacement).

Eventually I noticed that the park brake light on the dashboard (P6) did not come on much of the time, and that there appeared to be a relationship between that and the battery not charging.

When the tractor first starts up, that is usually the case.


Reading the diagram, the line that provides voltage to the park brake dashboard light (P6 on the diagram) is on the same circuit (ACC) as the alternator controller input (ON) when ignition is switched on.

However, with the working light also being on the same circuit (ACC) as the park brake light, I would have expected the working light not to be operational either. But that's not the case, so I suspect the circuit diagram is inconsistant with the actual wiring.

Everything works fine as long as I fiddle with the ignition switch until the park brake light comes on. Then the alterator works also (as confirmed by reading the voltage on the battery terminal).

Well, now to buy another new ignition switch... one that works .

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While mentioning brakes, I find the brakes on this tractor not very good. I hope never having to rely on the brakes to stop the tractor on a hill because THE TRACTOR WILL NOT STOP. It should have hydraulic brakes.