John Deere 326e charging issue

[JacksonG]

My 326e manual control has been giving low voltage warnings every time it gets started for a while, but it was functioning properly occasionally we’d have to charge the battery for it to start but not very often. We’ve tried to track down the issue several times and have had a service tech come out twice and look at it. We ended up replacing the alternator once already and the battery twice and still the issue continues. The other day it started going into limp mode, limiting the max rpm that it will reach at about 1800. It started throwing one code that is still active, 523694.12 which is the auxiliary input for channel 2 has a device fault, and has three stored codes one of which is the same as the active code, another is 158.01 which is saying the battery voltage from switched power is below normal, and 1485.02 which is saying is an ECU main relay showing erratic data. According to the wiring diagram that I have for the machine it is saying that there is a switched power relay which is connected to the auxiliary inputs, the alternator and the ECU which I believe might be the problem but I have no idea where the relay is. I uploaded the wiring diagram. Any help would be appreciated!

 

[Delmer]

I can't help you with the ECU, or the relay, or codes. Hopefully MG will be along and have some insight.

You say the tech has replaced the alternator and two batteries without fixing the issue, SOOOO I'm gonna start as the beginning. What is the voltage at the battery when it's running? You can run some tiny test leads to a digital volt meter in the cab to get an honest opinion. How often and how long is this used, roughly speaking?

If you don't find low voltage at the battery, move the test leads to the cab ground and a hot close to the ignition circuit, then the ECU if you can figure out the hot and grounds.

 

[mg2361]

Welcome to HEF Jackson!

Even if it seems tight, I would still recommend cutting it and installing an eyelet to the wire and attach it to the nut on the battery clamp. There could be unseen corrosion.

 

[JacksonG]

I can't help you with the ECU, or the relay, or codes. Hopefully MG will be along and have some insight.

You say the tech has replaced the alternator and two batteries without fixing the issue, SOOOO I'm gonna start as the beginning. What is the voltage at the battery when it's running? You can run some tiny test leads to a digital volt meter in the cab to get an honest opinion. How often and how long is this used, roughly speaking?

If you don't find low voltage at the battery, move the test leads to the cab ground and a hot close to the ignition circuit, then the ECU if you can figure out the hot and grounds.

The battery while it’s running is putting out 12.1 volts but it still shows low voltage and is in limp mode. It’s also pretty much always in use during the day so we barely have time to service it. As for the what to do with the voltmeter I dont think I fully understand what you’re saying.

 

[JacksonG]

Welcome to HEF Jackson!

Even if it seems tight, I would still recommend cutting it and installing an eyelet to the wire and attach it to the nut on the battery clamp. There could be unseen corrosion.

View attachment 259898

Thanks for the welcome! There is only one wire coming off of the battery and it is the main power. I think it all splits apart at the alternator where I checked the connector you circled and it wasn’t corroded at all.

 

[JacksonG]

I found the little wire hiding in the same sheathing as the main power wire as well and put an eyelet on it and it did not fix the issue.

 

[Delmer]

DUDE! I knew it was bad, but didn't expect it to be this bad! You threw codes at us so I assumed it was some magic MG voodoo and he gave it up, but we need an alternator to work if you want the codes to go away.

12.1 volts is almost dead. Check the voltage at the alternator B+ off and running. Check D+ (top wire in the diagram) off, with key on, and running.

You found low voltage at the battery, check the alternator next, not the ECU. ignore the other voltage checks I said earlier.

 

[mg2361]

What Delmer said^^^, but first, with wire connected, key on/engine off, what is the voltage at D+? What is the voltage on the D+ wire, disconnected from the alternator, key on/engine off?