JD 4100 HST Charge/discharge lights stay on after replacing rectifier/regulator modul

JimLAllen · Jun 27, 2017

Need help with electrical problem. I had a short in a add-on cable to operate a sprayer unit. The Voltage rectifier/regulator module burned out. Replaced this module and now The Charge/Discharge light stays on and there is 14.4 volts DC at battery terminals all the time. I have checked all the diodes and relays, they appear normal. Diodes V1 & V2 have a front to back ratio more than 10:1. All relays actuate and contacts operate. Tractor starts everything works except for the possible overcharging of battery.

Can the glow plug module cause this problem?

DFB · Jun 27, 2017

Usually when the glow plug module goes bad it stays in the closed contact position and continues to draw on battery voltage hence a continual state of battery discharge as the little ALT cant keep up with the power drain. In that situation you wont see 14V at the battery when running.

It's just timer that open and closes contacts for short duration just a few seconds really in the pre start key position

Easy enough to remove it from the system to check that if you want... just unhook the wiring connector plug!

You can always override the module by holding down the key in start position and activating a safety relay

Curious is your replacement regulator a OEM component?

I will take a look in my shop manual at the wiring system

DFB · Jun 27, 2017

Book shows me its the regulator that controls the light.

Battery power is activated in the key switch run position then off when engine starts regulator green/ wht/red wire to light red blk and blk wire to grd

JimLAllen · Jun 28, 2017

DFB said:
Book shows me its the regulator that controls the light.

Battery power is activated in the key switch run position then off when engine starts regulator green/ wht/red wire to light red blk and blk wire to grd

DFB: Thanks for the info. The module is an aftermarket product. It appears exactly like the factory minus the burned wires and is recommended for several mowers that use the Yanmar motor. Will start checking the wiring tonight. Thanks again for quick response!

DFB · Jun 28, 2017

You know I tried that once an aftermarket regulator for (grasshopper mowers and others I think) but didn't work out for me. I know how expensive the OEM part can be, but possibly the reg isn't cancelling the power after the engine starts and the alt begins charging.

A 14.4 charge rate is ok in my opinion (not overcharging) but also check and see if the voltage decreases slightly with a power draw...just turn the headlights on.

JimLAllen · Jun 29, 2017

I hope it decreased, I had to mow so I turned the lights on to take some of the charge current. I will be taking the it apart today, to check the wiring on the switch you mentioned in previous post.
when I took the old rectifier/regulator module off the wiring was burned about half way to the connector. I checked wiring on the harness side of that connector and it appeared normal. The connector itself was not distorted and appeared to work . I did notice the new aftermarket unit did not have as heavy gauge wiring as the JD unit, but could just be the insulator thickness.

JimLAllen · Jun 29, 2017

Tractor off battery voltage 12.75v; Tractor running 14.75v; tractor running, lights on 15.75v. Will remove shroud again this afternoon to start trouble shooting the start switch and reg/rectifier wiring. Thanks for your help DFB!