CHG Indicator MIA - JD 850

[Smedium C]

Hey guys, this is my first technical post. Thank y'all for all the previous help I've found through searching old posts. I've learned quite a bit from this forum already.

I have a John Deere 850 compact utility tractor. Not exactly sure of the year as the serial number plate was missing when I got it. From what I've read in the manual though it seems to be an earlier model as there is not a two-stage clutch.

The problem I'm having is with the CHG indicator light. When I first got it there was a parasitic draw on my battery which I tracked back to my indicator cluster. Bought a new one and replaced it. The CHG light was working fine but remained on. Did some more tracking and found my voltage regulator bad. So I replaced that. Before I was able to replace the regulator the CHG light went out. I had read that burning lamps was a common thing with these so paid no mind.

I've now replaced the regulator and the light bulb in the lamp assembly and still no CHG light. From what I have read this can cause a problem with charging as the light is the first step in the process.

Things I've tried:
Removed and cleaned fuse and fuse box connection.
Checked fuse plugs were in correctly
Cleaned battery terminals/ground
Cleaned alternator connections
Swapped old assembly with new bulb
Checked battery and alternator volts (battery voltage seems to be around the same whether engine is off or has idled and decent RPM - after idling goes up slightly. Alternator is showing very low to zero when connecting to terminal and ground and I think this has to do with the light)

I don't think these would have an effect but did it anyways. Is it possible the wire on the assembly has been fried? And can that be fixed?

If anyone has had a similar problem please let me know what the outcome was. I'm up for any ideas. Thanks.

Update: there's continuity between the voltage regulator and connector pin for CHG light. Also jumpered the lamp wire to main harness and grounded with no light. Must be an issue with the assembly. Anyone ever swapped out wires in one before?

 

[Smedium C]

Anyone out there? Guess I can only edit a post once. Disassembled the indicator assembly and there's not much to it. Doesn't seem like it's the problem.

Is what I read correct that if the CHG lamp does not work it affects the alternator charging up the battery?

I've been prodding around with the multimeter for a while now and all I've come up with is a 4ma draw apparently from my ignition switch. Not what I was looking for haha. Any ideas would be appreciated.

 

[Smedium C]

K7LN, thank you for the response. Wasn't aware that the battery was AC so I'll definitely check that after charging the battery back up.

The indicator light NOT turning on when I turn the key to ON position but not starting is the problem. It was working but staying on at first and now it is completely m.i.a.

All I was doing with the lamp assembly tests was checking if power would get to that light as it is not working but the temp and oil lights are. The oil light turns on in the ON position then cuts off when I start the engine as it's supposed to. The temp light flashes temporarily as I'm starting the engine then goes off. So those are lighting and yet the CHG lamp is not. However, I found continuity all throughout the wiring to the assembly so that doesn't seem to be the issue. I'm charging the battery currently and wondering if not enough juice in the battery could cause the lamp to not light. I'll know that shortly.

As far as I know the alternator, or dynamo, is the original. What AC voltage should I be getting from the alternator when I test that?

Thanks for your help.

 

[Smedium C]

After having the battery charged and the rain stopping I've hooked it back up and ran a couple tests. Looks like I have a bigger issue than just the light but they are likely related.

Battery tested 12.68V Hooked up and off
12.55V after starting and climbed back to 12.66V at idle. After running at ~2000rpms (no tach) the battery still tested 12.66V. Tested the alternator between the two wires in ACV and read 27.0. Then I decided to test ACV at battery and read the exact same 27 ACV.

So it seems like the alternator is working but not getting converted to DC if I'm understanding the VR function properly. The voltage regulator is brand new but that seems like the most likely culprit, no?

Strange that it charged back to near full at idle but didn't increase revved up. Also, while revved up I turned on the headlights and battery was quickly draining.

If anyone is bored out there and would like to chime in I'm all ears. Seems like three possibilities to me: dynamo, wiring, voltage regulator.

 

[Smedium C]

Thanks again for the replies. I decided to test the battery for ACV to see if it was receiving power but in the wrong form. And with the ACV numbers from the dynamo and battery being the same it seems that is the case. I've contacted the seller on the regulator and hopefully I can get a replacement.

Replacing the bulb is one of the first things I did. Even swapped them around to see if they'd work on the other lamps, which they did.
Will update with any progress.

 

[Smedium C]

I'm thinking that there used to be a few different voltage regulators but now they've all switched over to this single solid-state model. For instance, hoyetractor.com only shows a single regulator for an 850.

As to the alternator the parts catalog lists this as TY6647 - 12v/25amp nippondenso (sub for CH10493). I did a quick search and none of the distributors mention a rectifier but that doesn't mean anything.

I actually have a service manual and have run tests of all kinds leading me to the parts I had replaced. But it seems that didn't solve all the issues so I'll start retesting in the morning.

http://imgur.com/M8GdCbj

Sorry for the quality, best I can do for now. Not sure how to put the image in the post.

I'm obviously a novice so if you have any recommended starting points please let me know. This simple old 850 is a good tractor to begin on. Have to start somewhere.

 

[Smedium C]

Just saw your most recent post. You sure about the alternator? What you said earlier about it being a dynamo seemed correct as I was reading .0-.1 DCV yet getting 27 ACV when testing it that way. In you opinion, are the 27 acv at the alternator the same that are making it to the battery? I know it's possible but the VR is brand new. Would think something else is in play here.

 

[Smedium C]

Imgur: The magic of the Internet

The A connector has two wires as well.

A - one wire to the starter, the other to the ignition switch with a branch off to the VR

E - branches out to go to the headlights, VR, and speed hour meter lamp

N/F plug both go directly to the VR

No ground that I see. At the bottom of the picture, can barely see it, but the gray bolt just above the oil filter is also labeled E. The previous owner did have some mix ups that I found and repaired but this one seemed correct. I assumed that E was the ground which wasn't used.

Were you able to read the wiring diagram I posted at all? Only have internet on my phone but I can work some magic and get that diagram on here if not. Thank you for digging into to this, I really do appreciate it.

 

[Smedium C]

Just took the alternator in to test and it tested fine, churning out dcv.

 

[Smedium C]

All connections are clean on the alternator. The guy that tested the alternator said to turn the key to ON position and test field connection on alt which should be hot. I tested it and it wasn't hot, light didn't glow. However, I retested the wiring from the alternator to the VR and it shoes continuity. Plugged in, unplugged, all the same. Was he mistaken thinking there should be power there without the engine running or am I missing something? Replacement regulator on the way.

As to the regulator being grounded, I assumed it was grounded through the mount. That being said there is a blue wire coming from the new regulator that has a female bullit style connector which I thought would be for an accessory I didn't have (wasn't on the original). Looking a little more closely its tied in with one of the wires going to the field plug in the alternator.

 

[TimberHole]

I'm confused, maybe need to re-read the entire thread. The charge and oil pressure light should come on and stay on when the key is turned on. Does your light come on with the key (tractor not running)? The light should only go off when the engine is running. I assume it is triggered by the higher bus voltage but not 100% sure.

The temp light does not come on with the key but is lit when the sensor sees an over temp condition. Bottom line, when the key is turned you should see two lights, charge and oil pressure. If that's not happening it's probably just a fault in the idiot light circuit. Turn on the key and see if you have voltage at the idiot light.

 

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K7LN, I tried grounding that wire and didn't see any difference. If the VR they are sending as a replacement doesn't work I'll probably just return them both and get one from hoye. The eBay seller had good reviews so I went with it but I think hoye is going to be the more reliable source from now on.

Timber, the original problem was that the light wasn't coming on whatsoever. With the key turned to ON it used to light but no longer does. I didn't get a volt reading at the lamp but using a test light it shows there is power getting to it. Just not lighting. And the bulb has been replaced and swapped and replaced again. I'd like to have it working but it's not quite as important as the other two which seem to function okay.

 

[TimberHole]

This is the bulb I use. I tried to use some LED bulbs but they acted funky.


Here is the schematic

 

[Smedium C]

I'm using the same bulbs in mine. That's a fresh diagram, easy on the eyes haha. Honestly everything seems to be pointing back to the voltage regulator. Although power is getting to the CHG lamp so why it's not lighting is mind boggling.

 

[TimberHole]

Since there is only one hot wire that goes to the 3 light indicator assembly I think the bulbs get there ground at the 2 senders and the voltage regulator. I would disconnect the yellow/green wire at the voltage regulator and try grounding it. Am I reading that schematic right? I'll be the first to admit me and electricity just barely get along. I know the way to test the temp light is to ground the wire at the sender.

 

[TimberHole]

Here ya go, straight from the service manual....

 

[Smedium C]

I contacted the seller about the wire coming off of the VR and he said this was a ground wire. So taking what y'all said about me not possibly having a good ground while testing the light I went back at it using multiple spots. That's my fault, rookie error.

After finding a good spot, I grounded the VR and that seemed to cure the CHG lamp problem. It now glows although they're a bit dimmer. Once I decide on a final ground location I'll make sure it's nice and clean and maybe that will brighten them up.

Also testing around for a better ground i final got a decent reading on the alternator. It's still not churning power efficiently being at a nearly constant 12.4 (or really just matching what the battery has as every time I start the engine and the voltage drops so does the reading at the alternator). Sorry to waste yalls time on such a simple error.

Is it possible that the bench test of the alternator would produce a reading that wouldn't be consistent with actual tractor output? Because now it seems like the alternator is the issue.

 

[Smedium C]

Nix that last question. Looks like it is the voltage regulator. Even with the tractor running there are no volts getting to the field wire at the alternator. Continuity throughout both lines but just no juice passing through them. Unless there's something I'm overlooking.

Is there a way to circumvent the VR or is it a better option to keep it? Kind of an annoying little device haha.

 

[Smedium C]

I better not mess around with anything like that as I don't know near enough about it.

Sorry, with all the tests I've been doing I must have missed that one amongst them. Just tested at the F & N wires and I'm showing no voltage.

 

[Smedium C]

That'd be the one. I need to step my detective game up to where yours it at haha. Noticed the inconsistencies with the labeling but didn't think it went any further than that. I'll definitely shoot them a message. Seller is very responsive.

Yes, I still have the old mechanical VR. A lot of the wiring has either been chewed through or corroded. Figured I might get to rewiring it one day so kept it.

Imgur: The magic of the Internet