JD 1070 charge light help?

[Zeke56]

The charge light is turned off by two positive voltages. One positive comes from the key switch and the other comes from the alternator. When the alternator is not charging that circuit is negative and the light turns on. As the alternator starts charging that circuit becomes positive and turns the light off.

The first thing I would do is take a multi meter and check the actual volts that you are getting at the alternator and at the battery. There might be nothing wrong with the alternator and the fault might be all in the charge light circuit.

Good info right there, pmsmechanic.
We had very cold temps here a couple weeks ago. Below 10 degrees for maybe a couple weeks. The tractor started fine the few days I needed it. But, I kept it running mostly without lights and at rpms that wouldn't turn the charge light on.
If I run it with lights (charge light on) for long periods the lights will dim (battery dying).

 

[Zeke56]

I have a schematic that is called "New Version - March 1999" and the above is not the case. However, if you have a diagram of the innards of the VR, then the above might prove to be true with the "Old Version." My version shows one side of the bulb tied to ground. I'll dig through my books tomorrow and see if I can find the old version schematic.

I believe this tractor is a 94 or 95 but can confirm.
TIA for the old version schematic.

 

[pmsmechanic]

I have a schematic that is called "New Version - March 1999" and the above is not the case. However, if you have a diagram of the innards of the VR, then the above might prove to be true with the "Old Version." My version shows one side of the bulb tied to ground. I'll dig through my books tomorrow and see if I can find the old version schematic.

I'm just gong by how it works on a Delco alternator. I don't have access to a service manual to try to figure it out.

 

[rScotty]

All of the information posted so far seems to point to a weak alternator.
rScotty

 

[Deleted member 216442]

All of the information posted so far seems to point to a weak alternator.

rScotty

I have a 1070 bought new in 96 so it is approx. same vintage. I've been running one auxiliary light (sometimes) all those years with no issue. It does sound like a weak alternator. I would check voltage at the battery while it is idling with and without the lights on, and with and without the auxiliary lights in the circuit. I would assume voltage should be more than 12. I can do tests on mine if you need comparative numbers. I just installed a new battery this summer - it is the second one in 21 years.

 

[rScotty]

Hey, that's great. Now we have one 1070 that charges right and one that doesn't. This should make it easy. All we need is to put a voltmeter across the battery and an ammeter in series with the + lead to the battery. Then we record those two readings at rest and at various RPMs, with and without lights on.
If the batteries are good, doing that test should tell us all we need to know.

Start by recording the volts and amps with the motor off and lights on at 5 minute intervals until the voltage drops below to 12.2 volts or so. Try not to go to far below 12.2 volts. That will tell us the basic state of the batteries.

I sure do like those 1050/1070 series JDs. Some of the best.
rScotty

 

[pmsmechanic]

I looked at the "Old Version" that I found in my tech manual and the charging circuit is identical. One side of the bulb is tied to ground and the other side goes to the VR.

So a double negative turns it off?

 

[TimberHole]

I'm no electrical expert but if I had a persistent electrical problem with one of these tractors I would not only check the battery to frame ground but I would also check the engine to frame continuity. Some of the components were painted before assembly and the ground was carried in the connection bolts. As an example I have two JD 950's and none of the rear lights worked because the rear fenders had lost their ground. Apparently the design was adequate when the machine was new but failed with age. I have added ground straps to solve the problem.

 

[Zeke56]

The serial number will confirm it for you.

1989: 001001
1990: 001338
1991: 100001
1992: 115001
1993: 120001
1994: 130001
1995: 140001
1996: 150001
1997: 160001
1998: 170001

Thanks, I'll check it tomorrow.

 

[Zeke56]

I have a 1070 bought new in 96 so it is approx. same vintage. I've been running one auxiliary light (sometimes) all those years with no issue. It does sound like a weak alternator. I would check voltage at the battery while it is idling with and without the lights on, and with and without the auxiliary lights in the circuit. I would assume voltage should be more than 12. I can do tests on mine if you need comparative numbers. I just installed a new battery this summer - it is the second one in 21 years.

Thanks for your input, I'll get back to you if I need numbers to compare to.
I will be checking the alternator again.
Love your first battery! Hope the new one lasts as long.
See my answer to rScotty also.