John deere 755 light issues

[noble527]

Hello all, I have purchased a john deere 755 about 4 months ago, and every time I turn lights on my battery light becomes dim, they all work, and battery is charging. I have a feeling it is ground related. I installed a rear work light with factory connector (went led) and it wouldn't light at all. I checked voltage and im only getting around 10 volts at the plug, and that is the same for the fender lights, which still light up. I checked power coming out of ignition switch and its reading 12 volts to the light switch. I did replace light switch when I bought because it was wore out, however it still did it before new switch too. I was curious where the ground location was for rear lighting. I have a high resistance to ground.. I did find the ground behind side panel, bolted on steering column, but besides that and engine ground I haven't found any. It is showing on wiring diagram that there is a separate ground for the rear lights. Any ideas? Thanks!

 

[pmsmechanic]

Battery lights work by feeding two positive wires to a light bulb. If the alternator quits charging the wire in the alternator starts to ground out. If the light goes on during heavy use it's usually a sign that the alternator is getting weak. Check the charging voltage with the light's off and then on. there shouldn't be much of a difference in volts.

LED's are polarity sensitive. In other words they don't work if the wires are hooked up wrong.

 

[noble527]

I have checked battery voltage when running, its running upwards of 16v charging, which seems high. I also have double checked my led, and it is hooked up correctly. I believe for an led light to work it has to have at least 12 volts, which since im only getting 10 volts to all the rear lights I believe that's my problem. I just don't know where to look or different ground locations. Its driving me insane.

It seems that the battery light is always dim, just becomes brighter when I turn on lights. As I said it is showing 16 volts when running, and changes very little with lights on. Still doesn't make sense why im only getting 10 volts back at my light plugs.

 

[BBO]

I just don't know where to look or different ground locations. Its driving me insane.

See if you can open the attached pdf that I found. I think it has like 3 or 4 ground straps.
View attachment 755_Ground-Circuits_410.pdf

 

[pmsmechanic]

I have checked battery voltage when running, its running upwards of 16v charging, which seems high. I also have double checked my led, and it is hooked up correctly. I believe for an led light to work it has to have at least 12 volts, which since im only getting 10 volts to all the rear lights I believe that's my problem. I just don't know where to look or different ground locations. Its driving me insane.

It seems that the battery light is always dim, just becomes brighter when I turn on lights. As I said it is showing 16 volts when running, and changes very little with lights on. Still doesn't make sense why im only getting 10 volts back at my light plugs.

16 volts is high. It can be there shortly after you start the tractor but should settle down to 13.8-14.5 volts. Just for the fun of it check the volts at the rear plug with the other end of the volt meter hooked up to the negative on the battery. That will tell you if it's a ground issue or a wiring issue.

Some led's I've seen are rated for 6-24 volts. Just though I'd throw that in.

I had the same problem with my F935. The battery light would sometimes glow and sometimes not. It would usually glow with the lights on but not always. I took the alternator in to a local store and they said the charging was good so I just lived with the problem. Usually about three times a summer I would have to recharge the battery. Finally I just couldn't mow at night any more so I took the alternator to a rebuild place and they rebuilt the alternator. End of problems.

 

[noble527]

Well located all grounds and cleaned, and moved ground strap that wasn't placed right. fired tractor up and was much happier with voltage, battery settled down to about 14.6 volts wot, light worked and were getting proper voltage. Next question, I observed voltage when I turned lights, and it dropped about a bolt and a half. Normal? I did notice battery light dim then and also would sometimes pulsate also. I'm assuming I'm going to have to have alternator rebuilt at some point, but never has had a dead battery. Ideas? thanks so far!