JD 410B Backhoe - Alternator issues

Hello,
I've had to replace my alternator due to failure of the original. Prior to putting in a 65 Amp alternator, I attempted to use an alternator and regulator I had sitting in a Ford Ranger. That didn't work because of either a bad wiring job, or a poor regulator. I'm betting I wired it incorrectly.

In any case, when looking for alternators, the OEM is often pointed out to be an IR type alternator, I don't believe that Ford fits the bill, perhaps why i had so much trouble.

All of the above is just background.

I've put in an alternator meant for a later-model 410B or 410C. The 410 originally came with a 37amp alternator which worked I suppose. The 410C had a 65 amp alternator with a different and somewhat more rugged regulator on it. The 410B (what I have) split the difference, some getting the 37 amp alt, others the 65.

So, I wanted more power to help charge my new high-current gelcell batteries.

I've got every thing working as expected, save for the tach and alternator lamp. What happens is this:

I have the engine turning at 1500 rpm. watching the tach and alternator lamp, I see tach hold steady for 6 out of 7 seconds, and that 7th second the tach drops to about 1000 rpm, and the alternator light turns on. This cycle repeats over and over. I've not tested different rpms.

Note the engine sound doesn't change. The voltage sense on the regulator shows 0.2vdc for those 6 seconds, then spans 5 volts for the 1 second.

Where is this duty cycle coming from?

not sure if I'm asking in the right place, but i've given as much information as I can.

thanks,
Jack

Welcome to YT
Have you considered installing a Delco 10SI one wire alternator?

410B used Prestolite-Motorola alternators with piggy-back reguators. 37, 51, or 65
amp. Why not just fix what you have or a brand new 65 amp with reg. is only $90.

There is no "high" charge current needed for those awful gel-cell batteries if that is
what you prefer.

What drives your tach? I don't remember. If it is electric and not mechanical drive,
it likely runs off the stator in the alternator.

Also what specific alternator did you use from a Ford?

"tach drops to about 1000 rpm, and the alternator light turns on."

If he uses a 1 wire he loses the alternator charge indicator light function.

Get 3 wire Delco, connect alternator end of charge light to terminal #1 of edge plug. Loop #2 on edge plug to output or other battery source

Single wire alternator, right, while simple, doesn't have a pretty high cut-in charge rpm? I see many people using them, but i don't tend to run the old gal over 1500 rpm.

(quoted from post at 08:19:12 05/06/17) "tach drops to about 1000 rpm, and the alternator light turns on."

If he uses a 1 wire he loses the alternator charge indicator light function.

Get 3 wire Delco, connect alternator end of charge light to terminal #1 of edge plug. Loop #2 on edge plug to output or other battery source

Click to expand...

Okay, I've sorted out what it is after monkeying around with it. The regulator sees the battery is near full and is cutting power to it. when I load the alternator a little - turn on the lights, everything evens out.

Right now, my tach is electrically driven off one of the diode posts in the alternator. I'm thinking this isn't all that reliable, I'm probably getting a great read on how fast the alternator is spinning, but not so much on how fast the engine is spinning, given this is meant for a different alternator.

(quoted from post at 06:19:58 05/06/17) 410B used Prestolite-Motorola alternators with piggy-back reguators. 37, 51, or 65
amp. Why not just fix what you have or a brand new 65 amp with reg. is only $90.

There is no "high" charge current needed for those awful gel-cell batteries if that is
what you prefer.

What drives your tach? I don't remember. If it is electric and not mechanical drive,
it likely runs off the stator in the alternator.

Also what specific alternator did you use from a Ford?

Click to expand...

yep, that's what I did, I've got the 65 amp. Used to have the 37 amp on there. The regulator looks a bit different, but after just carefully reading instructions, and looking at the wiring diagram, it went in, and I didn't let any of the secret smoke out!

The alternator I used from a Ford, well, I don't know which one it is, I still have it, seems it's fine (after measuring the resistance of each of the windings with it all apart). when I get back in tonight I'll let you know. My problem with this setup was the regulators, not the alternator itself. Must have been doing it wrong is all, I smoked two of those Ford regulators - granted, both were spare/junk vehicle pulls, so no guarantee the regs were OK or not.

There is nothing inherently good about a Delco 10SI with a self-exciting regulator
except the simplicity of hookup. It does not sense battery voltage correctly, does
not cut in as early as the standard two wire connection, and not all that easy to use
with a charge-indicator light. Older diesel electric tachs work off of stator-taps.
If the tap is the same on the new alterator, and it has the same sort of stator, and
the pulley size is the same -tach will work fine.

Okay, ran it most of the day. Battery stays at 14.43 Vdc. By playing around with lights, etc, several starts, stops, measurements, I've learned a bit about how this alternator functions.

Engine stopped, key to acc, all 4 lights on for 15 minutes, start the engine. Engine rpm 1500, tach showing 500, voltage at tach sense about 3.5vdc. After about 30 seconds holding 500 rpm on tach, it springs up to 1500, then switches to approximately 80% duty cycle - deduced by watching tach hold steady and then drop for a bit, hold steady, etc.

When the battery is as full as it's going to get, the tach will show the alternator in a 50% duty cycle. It stays at 1500 for 3 seconds, then drops to zero for 3 seconds, cycle repeating.

I like the alternator, and am going to replace the tach and hour meter. Looking at the crank to pump connection, I believe i can set up an induction sensor to determine actual crank rpm, which should be more accurate than using a stator connection. Certainly when you consider the alternator has no interest in making sure the tach works at the expense of damaging the battery.

Overall, this has been a good bit of learning, I'm quite happy with the outcome. Once I have an accurate tach, I'll be very happy with the whole thing.

thanks for your time and responses. I've been a lurker for years, first time posting, was a positive experience. thanks again!

Jack