Charge Light Staying On - Redux

[Tom_Veatch]

I've been following the similarly named thread and followed the advice therein, to wit, voltage measurements, etc.

So, for the Yanmar doctors/diagnosticians in the audience, the patient is a YM2220D with about 625 hours on the meter. To the untrained observer's eye, all the electrical components appear to be factory type. There do not appear to be any after-market or 3rd party components installed.

Patient complains of a charge light which is almost always on, but after a few minutes of operation, the light may go off. However, this is rare. Most of the time, estimated in excess of 90% of the time, regardless of engine RPM, the light shines brightly. If the light goes off, it has not been observed to come on again prior to engine shutdown.

Patient presents a voltage across the battery terminals with the charge light illuminated as follows:

• Engine Off: 12.6v
• 800 RPM: 13.4v
• 1500+ RPM: 14.3 to 14.6v

1. An AC voltage exists at the output of the alternator.
2. Charging current has not been measured.
3. There has been no difficulties in starting. The battery has been adequately charged at each engine startup.
4. Measurements have not been taken with the charge light extinguished as the opportunity has not presented itself.

OK, any ideas for this raw intern (other than putting a piece of tape over the charge light)?

 

[kenmac]

loose or bad wiring comming from the alt. volt. reg.to the light ? Something in the alt. voltage reg. is about to go out & it is giving you a warning ? Just thinking here ( if that's possible )

 

[Tom_Veatch]

loose or bad wiring comming from the alt. volt. reg.to the light ? Something in the alt. voltage reg. is about to go out & it is giving you a warning ? Just thinking here ( if that's possible )

I'm certainly leaning in that direction. Obviously the alternator is doing it's job. The expected value of DC voltage is being applied to the battery so that part of the regulator function seems to be OK. And I'm assuming that Ohm's law hasn't been repealed so there should be a charging current. But whatever subsystem controls that durn idiot light sure has it's hat on backwards. Maybe I should just install an ammeter and put that piece of tape over the light.

 

[kenmac]

Maybe I should just install an ammeter and put that piece of tape over the light.


Or just disconnect it. With a volt or amp gauge you won't need the light & you can tell if all is doing it's job at all times

 

[gemini5362]

I might check my grounds to see if one of them has a high resistance connection. ( For example corrosion around the connection or a loose wire) If your circutry that determines there is a charge failure has a high resistance connection it would show lower amperage through that connection and might give that indication. The light going off occasionally would mean that conditions were right for a better connection and it showed a normal current. I would definetly check all the grounds going to the engine and the instrument panel.

 

[normde2001]

It's most likely the regulator. I believe I read somewhere there is a screw adjustment to control the voltage at which the light comes on.

 

[Mickey_Fx]

I'm with Norm and the others that are thinking v-reg is the issue. Looking at the schematic for my series tractor, the lamp gets its power from the v-reg. So unless something has changed, and power is coming from some other source, the v-reg determines when the lamp is on-off. A bad ground can affect whether the lamp comes on at all but can't be the source of the problem if the lamp is on most of the time. Don't know it there is an adjmt to control the lamp.

 

[Tom_Veatch]

I'm fairly convinced the problem is at the regulator. Whether internal or in external wiring is not yet clear. I pulled the regulator, looking for any adjustments. None. It's a completely enclosed, potted(?) unit.

The schematic shows 6 circuit paths to/from the regulator which agrees with the physical number of wires. Tracing those paths on the schematic, it looks like a fault in only one, the regulator's ground connection, could be the problem. A fault in any of the others would show problems not in evidence. Don't have a schematic of the regulator guts, so I don't know what effect a faulty ground connection would have on the regulator electronics, but it's quite possible it could mess up the operation of one or more semiconductor devices in there.

I've cleaned and reseated the connector a couple of times, wiggled the wires around and reattached the regulator - giving any broken wire plenty of opportunity to separate.

The last couple of starts has shown the light acting right so maybe cleaning the connector cured the problem. If its a broken wire that was reconnected by the wire-wiggling, it should re-separate with operating vibration. We'll see what happens over the next few tach hours.

I suppose it's still possible that the internal device(s) controlling current to the charge light could be flaky. Which may be the more reasonable explanation. I'd expect a faulty ground to affect more than just the charge light. But with a sealed unit and no circuit diagram, it's hard to tell.

 

[LMTC]

The technical information in this discussion has left me in the dust....quite a few posts ago. What I can add is that the replacement does have 6 wire leads ending in a 6 terminal rectangular plug, though I couldn't begin to tell you what any one of the wires is for. It fits a wide range of models, some of which have a 4 wire plug (for which we have an adapter to fit this VR) if that tells you anything.

Oh, and we can get that to you in a couple of days if you want to order one.

 

[Tom_Veatch]

...Oh, and we can get that to you in a couple of days if you want to order one.

The 6 wire, rectangular plug is the right interface, and I might want to talk to you about a replacement if/when I decide this thing is beyond hope. Right now, 'though, it seems my speaking sternly to it earlier today had the right effect. The charge light was behaving itself and the voltage across the battery was gradually building back up from the starting drain when I ran it up a few minutes ago. (I don't suppose the box/package/etc. they come in has a wiring diagram/schematic attached, does it?)