656 charging issue

[Saucymynx]

Hi there. I hope you all can guide me in the right direction. I have a Farmall 656 with 12 V electrical system. A few weeks ago I was working out after dark with the lights on and after about an hour they became very dim. I pulled into the barn, shut it off and then immediately tried to restart it. The battery was dead. I put a charger on it overnight and it started up fine the next day. I went out today to run it and the battery would not turn over the engine. I checked the battery voltage and it was 12.3. I cleaned the terminals and put the charger on it but it didn’t seem to take a charge. Since the battery was from 2016 I figured I might as well just replace it. So I put a new battery in along with a new starter cable and she started right up. When I put the voltage meter on it with it running at pto rpm’s The voltage across the battery terminals was only 13. I thought it was supposed to be in the high 13‘s to 14 range. Does it sound like I have a charging issue? Automotive electrical systems are a bit mysterious to me, so I appreciate any help you can give me. It is a gas engine by the way. Thanks

[outdoors4evr]

13.1 "seems" a bit low. Being that it didn't keep up with the lights, I'd suspect the voltage regulator (if equipped) or the alternator/generator.
The cheapest way to start is to take your alternator to a car parts store and have them load test it. They of course will want to sell you a new one.

[Gary Dotson]

I believe the alternator on that tractor is the very popular Delco 10si. They are incredibly serviceable and also about the least expensive alternator. If you have a shop, in your area, that does starter / generator repair, they can test it and fix it easily. You can also take it to an auto parts store, as mentioned above, and if it test bad (it will) and exchange it for a re-man unit. They sometimes offer brand new ones for just a few dollars more. You might also look on-line at DB Electric, they generally have good prices. Your voltage at the battery should have been 14.2 - 14.5.

[Saucymynx]

Thanks for the great feedback and suggestions. I will find someone to load test the alternator and see what they say. I will report back what I find

[Tired_Iron]

If the main parts of your alternator are in good shape, you can get repair parts to replace the defective parts in the alternator at a local auto parts store, such as NAPA.

Also to test the alternator, there is a test hole. You can ground the field winding tab to the case by inserting a screwdriver into the hole. Be careful, the tab is within 3/4 inch of casting surface and should be able to see it. Do not force screwdriver deeper than one inch into end frame. The engine must be running and use precautions when working around moving equipment.

If the alternator fails this test, there is something else happening, but if it comes to life the integral voltage regulator is faulty. The slip ring brushes are also likely worn as well. These alternators are easy to work on. There are service manuals out there on the Web.

10Si Alternator Identification.png (32.62 KiB) Viewed 1524 times

[Eugene]

I no longer to repair alternators. I purchase a replacement for about the cost of the individual repair parts, and they come with a one year warranty.

[Saucymynx]

Could it be… I just went out and took a look at the alternator. I checked the belt tension and lo and behold it has about an inch of deflection with no pressure. The manual says 5/8 to flexion with 25 pounds of pressure. Could this be the problem? Either way, it does need to be tightened up it could it be so simple? Also, my alternator does not look like a 10 SI. It has a plug for two terminals and several other connections. I’ll post a picture of it soon. Thanks

[outdoors4evr]

A loose belt is certainly worth investigating.

[Gary Dotson]

Very definitely! I should have thought of that, had that issue on the neighbors tractor recently.

[Tired_Iron]

As said above, certainly a possibility!

[Saucymynx]

Well, it couldn’t have been that easy. I tightened the bell up but it still only shows 12. 8 to 13 V across the battery terminals with the engine running and about 1000 RPMs. Back to the drawing board

[Tired_Iron]

Well, if your alternator isn't an Si series alternator, it is likely one with an external regulator. You have a couple of options at this point. It could be the alternator, the regulator or broken wires in between. The most economical fix may be installing a one-wire alternator, but that is up to you. They should be available from NAPA or the likes for $75 - $100 or so.

On a side note, they used to make regulators with a cover that could be taken off. If this is the case, remove the cover and see what is going on in there. Might be as simple as dirty contacts.