Deere alternator questions

I was trouble shooting the non-advancing hour meter on my 5500N yesterday. Following the Technical manual instructions, I got to the step to verify alternator output- had battery voltage at the big lead and also at the IG terminal with KOEO. When testing at low idle, I had no voltage at the L terminal, which feeds the hour meter and charge indicator light. I do not have a charge indicator light lit in either condition. The tech manual says voltage regulator failed, replace alternator.

This seems reasonable, I guess. The battery has been staying charged and the other electrical items seem to function correctly. I did not take a voltage reading at the battery while it was running.

I can get a reman on prime for under a hundred, or on flea bay for $125, or from the dealer at $461. There is also a package on theBay for a replacement voltage regulator and brush holder/brushes combo for $35. Assuming no obvious issues in the alternator (bad bearings etc) I'm thinking it can't be too hard to swap out VR and brushes, can it?

I reposted this here after no response on the JD forum, hoping to catch a couple of the experts who might not dig into each manufacturer board.

What brand of alternator? I've worked on the Delco Remy 10SI and 12SI. They are reasonable to work on. Get a copy of Delco Remy Service bulletin 1G-266. Lots of good info that should apply to any alternator. A good quality multimeter is needed though to get good readings of the diodes, etc. I have a Fluke 73 III multimeter.

Something that isn't very obvious is the placement of the brushes when time to put it back together. The brushes have to be placed in their sockets and held there by a restraint. I use a small drill bit that is long enough to reach through the end casting and is pulled out after the castings are fully in place. This frees the brushes to be pushed against their slip rings.

I can tell you this by looking up the alternator for your tractor it is not a Delco 10 or 12si model. I have never been
in one of those newer alternators and I do not even know if that is a Delco brand alternator. I can tell you this I
replaced a voltage regulator in a Delco alternator on a 99 Buick Lesabre and it had two connections that needed
to be soldered in. If I remember right the rest of that alternator was similar to a 10si as the diode bridge had 3
studs with nuts that the stator lugs were fastened on. I personally think I would just give up the $100 and get one
that bolts on.

If I was diagnosing a mal-functioning speed/hr meter I'd be checking the speed/hour sensor not the alternator.

It's probably a denso or bocsh. A delco I use a tooth pick for the brush retainer till I get it together then just pull it out. a small wire will work as long as it will fit in the hole and pull out .

Thanks for the replies!

It is a Denso brand alternator, Deere part RE72917, 60A.

I had the chance to pull it off and swing by the repair shop yesterday, he tested it and determined it to be fine, charging properly, and providing voltage at the IG terminal. He said he did not know what the L terminal would be for, nor did he test it there.

I removed the cover before re-installing and blew out all the debris. The VR did not show any external signs of damage and the brushes looked to be in fine shape without disassembly.

When I re-installed the alternator, it initially tested to have battery voltage at the L terminal at idle, but the meter did not advance while I sprayed in the vineyard after that.

TxJim- I am confused, because the Deere Tech manual has no reference to the engine speed sensor in the section for troubleshooting the hour meter nor is it shown on the system description of the hour meter wiring diagram. With 23 test points in the procedure, from battery through alternator and relay to the meter and every harness connection in between, it seems pretty thorough.

I have replaced the engine speed sensor and the tachometer works fine, as far as I can tell.

My knowledge of newer JD tractors is very limited. But I was thinking older hour meters were controlled by speed sensor. Which tech manual are you referencing?

It's out in the barn, I 'll have to get back to you...Thanks, your vast knowledge and willingness to share it makes this site very helpful. I appreciate you and the others who are able to help with real operating experience.

You're welcome
Due to alternator checking out I also suggest to check/clean/tighten instrument panel ground(negative) connection to tractor frame.

I don't want to confuse the issue, as I know nothing about this tractor. I can only ask questions, and share my experience. Forty
some years ago, while working on tractors, electronic tach's and hour meters appeared. Are yours separate, or together? The hour
meters I remember from that time did not care about the tach, nor engine speed. They required two things to count hours- battery
power from the ignition switch, and a signal from the alternator that it was turning. So, if the key was accidently left on, no
hours counted up. And whether idling, or wide open, the hour meter ticked off the hours just like a clock.

Toothpicks work good for holding the brushes back.

(quoted from post at 06:27:47 07/02/22) Toothpicks work good for holding the brushes back.

Click to expand...

The round ones work best! :lol: :lol: :lol:

Bob- the tach and hour meter are on the main dash cluster, but appear completely separate. The hour meter uses a battery voltage feed from the "L" terminal of the alternator, which should only be 12V when the engine is actually running, not even just a Key On/Engine Off situation, to avoid running up the hours if the key is left on. I may try to hot wire the hour meter with a 12V source to see if it will advance.

The only reason I am messing with this now is that I wore a hole in a steel hydraulic line from the steering valve at the dash running forward to the steering cylinder at the front axle. I had to disassemble the hood, cowl and dash panels to get to the valve to replace the line, and figured it was a good time to trouble shoot since it was already torn apart.

I thought I might actually have to split the tractor to get that line in/out- it has like 34 bends in about 48 inches length. I did unwire the alternator and block heater, remove both brake lines, remove the high pressure pump suction and discharge lines in addition to the bodywork removal. I probably had eight hours of time in the R&R of that line alone, the hour meter is just an annoyance that got worked out of convenience.

TxJim- I was using TM1585 Technical Manual, hour meter system test starts on page 240-15-120

I was just curious if you had correct manual for your tractor model & that manual is the correct one for your tractor.
What are the eyelets encircled in green in parts photo designed to do? Do they serve as ground connections?

My manual is specific to the 5400N and 5500N Narrow tractors, and dated 09DEC96, which should be after my tractor build date.

What I will need to look for is CTM77 for Alternators and Starting Motors, to verify that my alternator should be outputting "battery voltage to 1.5 volts less than battery voltage" at slow idle and "1.5 volts maximum" at key on/engine off. I show no voltage at KOEO, and actually detect a ground in that condition. Only one time have I probed and gotten 12V from the L terminal while idling, every other time I get no voltage.

Yes, those two ring connectors attach to a ground block on the firewall.