6640 intermittent electrical problem

[Jackfr]

My 6640 has an intermittent electrical problem. Sometimes the battery indicator light comes on dim, you only can see it when it's dark. Other times it will continually blink on and off. But with both conditions as soon as you shut it down and restart the light goes out and it acts normally. Then the next 4, 5 , 6 ... times it runs ok. So by the time I go grab a meter it's running ok again. With winter coming on and all the electical assist controls on this tractor (4X4 Diff lock Heat etc.) I would like to find the problem before it really dies probably in the middle of a snow storm at night. Anyone have any ideas on where to start looking.

Thanks in advance for your help

Jack

 

[RickB]

Probably a weak or failed diode in the alternator; especially if the alternator is charging while the light is lit/flickering. The PTO clutch circuit depends on a 'W' signal from the alternator, so if it isn't charging, you won't have PTO. Just so you know about that little trait they have.

 

[Jackfr]

Thanks Rick. What do I need to do to check for this. Is there anything in the service manual or service bullitins? During the summer I was having intemittent PTO problems also until I jumped out the module in the fuse panel. If the alternator stops charging does the 4X4 stop also? This charging problem seemed to get worse after I pressure washed the tractor to take apart and repair the 3 pt hitch problem I had earlier this fall.

 

[RickB]

Check the circuit from the key switch through the instrument panel charge light to the alternator. Make sure that with the key on, there is steady voltage supplied to the alt by the appropriate wire. The idiot light bulb is a different wattage than most of the other indicator bulbs; it has a different color base. If the exitation circuit checks out, have the alternator tested, not only for output, but diode conditiion as well. The 4WD switch will operate on battery voltage, power to the 4WD solenoid DISengages the 4WD clutch. Spring pressure applies it. Cleaning all the chassis ground locations may help any and all the above. Ground locations should bein your service manual.

 

[Jackfr]

Thanks for the info Rick. I'll check the circuit on Monday as I'm working again tomorro and post what I find.

Jack

 

[Jackfr]

Sorry so long to repost. It just starting acting up again yesterday (dim idiot light). We checked the lead from the key switch through the idiot light and it appears fine and cleaned all the grounds. The light is still coming on dim when its running though but only sometimes (1 time in 10) which makes it harder to find the problem. The service manual says to pickup a 1100 ohm (I think but will recheck) resistor and make up a tester to check the battery temperature sensor. Any idea what wattage I should get at radioshack? The battery sensor is floating around on top of the batteries. What is the battery temp sensor for? To protect the batteries from overheating when being over charged? They are outboard under the right step is this necessary or is this another of the redundant safeties I have found on this tractor? I thought I read somewhere that this was eliminated on all the new replacement alternators? The only thing I didn't check was the voltage output of the alternator. I was thinking of adding a voltage guage to watch it when it started acting up. I was planning on installing it on Tuesday to keep an eye on things. Should I add an amp meter also? One other observation is when spreading manure tonight after work with all the lights radio and blower on the idiot light went out completely. Working again tomorro so next day to work on this is Tuesday.

Thanks again Jack

 

[RickB]

You have a bad diode in the alternator. Haven't seen those symptoms since Friday. You can check the battery voltage when the light is on or flickering and likely find the alternator is charging. Then decide if the idiot light really bothers you enough to replace or repair the alternator.

 

[Jackfr]

I plan on adding the volt meter to the dash that way I'll know what's going on. If it's still charging there is no reason to replace diodes until it stops charging at that point should I replace just the diodes or buy a rebuilt alternator? My problem was with the idiot light flashing and/or on dim I didn't know what was going on. Is there anything else that I have to watch for that is driven off the alternator? Do I need the battery temp sensor? This is the only piece of equipment I own that has one all the others work fine with out one.

Thanks for your help Rick I'll let you know how I make out.

Jack

 

[Jackfr]

Installed volt meter today. Battery shows 12.2 volts before starting and a constant 13.9 volts while it's running, even with all the lights and heater on. But the idiot light is still on dim when the lights aren't on.

 

[RickB]

Well you need to decide just how much that light bothers you. I know of a TN75 that does the same thing. It has for about 4 years now, and the battery stays charged as well as a tractor with a properly functioning charge lamp. A short piece of black tape may be in order.