# A simple alternator test?



## maxreco (Sep 30, 2015)

Full disclosure: I have no electrical knowledge, and have always believed that electricity is proof that devil lives amongst us. That being said, I'm trying to chase an electrical issue on my Ford 1620. I disconnect the negative battery terminal while the engine is running, the engine stops. Does this indicate the alternator isn't good? I also see no change in battery voltage when engine is off or running. Does this test prove the alternator is bad?


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## Fedup (Feb 25, 2014)

It's often perceived that disconnecting a battery cable while running is a "test" of charging system. While it may be true in some cases, there are far too many different systems out there to make it a blanket statement. Personally, I view it as more a risk than a test.

The 1620 would have an internally regulated alternator which would require an exciter signal, probably from the instrument panel circuit through a charge/indicator light. Does that work? Meaning does a battery light come on when the key is turned on? Your problem could be as simple as a failed bulb. Beyond that you will need to do a bit more testing before condemning the alternator. Have you checked to see if the fan belt is tight enough to turn the alternator?

Some would suggest you "take it to your local XYZ auto parts, they will test it for free." Maybe so, but if they tell you there's nothing wrong with it, you still have to go home home and figure out what's really wrong. Why not check a few simple things first?


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## Bob Driver (Nov 1, 2017)

Simple alternator test using a VOM(multi-meter)….
*Key off -*
1) Red lead on +, black led on - battery post
2) Read battery voltage (should be between 12.3 and 12.7V, for a fully charged battery depending on ambient temperature)
*Engine Running -*
1) Red lead on +, black led on - battery post
2) Read battery voltage (should be between 13.8 and 14.5V (at *full throttle*)

If the voltage reading does not increase with the engine running, the alternator is *NOT* charging the battery.

If the reading is in the low 13V's....

*Testing the charging wire from alternator to Battery-*
1) Red lead on alternator output terminal, black led on battery + terminal.
2) More than .5V means the wire has to much resistance (corroded, or overheated) and needs to be changed
3) If the alternator is not internally regulated (separate voltage regulator) Use the same test method on both the wires going into the voltage regulator from the alternator and coming out of the voltage regulator to the battery.
4) The voltage difference between the input wire from the alternator terminal to the voltage regulator and the output wire from the regulator to the battery is the amount being "regulated".

14.7 going into the regulator, 0 coming out- Regulator is not working... Replace, or adjust (old school mechanical regulator)


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## maxreco (Sep 30, 2015)

Fedup said:


> It's often perceived that disconnecting a battery cable while running is a "test" of charging system. While it may be true in some cases, there are far too many different systems out there to make it a blanket statement. Personally, I view it as more a risk than a test.
> 
> The 1620 would have an internally regulated alternator which would require an exciter signal, probably from the instrument panel circuit through a charge/indicator light. Does that work? Meaning does a battery light come on when the key is turned on? Your problem could be as simple as a failed bulb. Beyond that you will need to do a bit more testing before condemning the alternator. Have you checked to see if the fan belt is tight enough to turn the alternator?
> 
> Some would suggest you "take it to your local XYZ auto parts, they will test it for free." Maybe so, but if they tell you there's nothing wrong with it, you still have to go home home and figure out what's really wrong. Why not check a few simple things first?


I verified the battery light bulb was good, but it never lights up, even when the key is turned. I also have checked belt tension is good.


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## maxreco (Sep 30, 2015)

Bob Driver said:


> Simple alternator test using a VOM(multi-meter)….
> *Key off -*
> 1) Red lead on +, black led on - battery post
> 2) Read battery voltage (should be between 12.3 and 12.7V, for a fully charged battery depending on ambient temperature)
> ...


Thank you Bob and also Fedup for your excellent suggestions. When I tested the voltage while the engine was running, I didn't go to full throttle, so I will recheck, and also appreciate the test procedure for the alternator output. I have no idea where to find the voltage regulator so I assume it is internal.


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## marc_hanna (Apr 10, 2017)

I set my multimeter on record function to track spikes and dips in the voltage while revving it. Either can indicate a failing regulator.


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## Bob Driver (Nov 1, 2017)

I'm pretty sure the alternator on 1995 tractor would have an internal regulator. One of the most common alternators in use at that time was a Delco-Remy 10SI 63 amp alternator(see picture below). You can tell a 10SI by the fact that it has 3 cooling inlet slats at the back, there is only 1 large wire stud coming out the back of the alternator, and there is a large two-prong wire lead coming into the top of the housing. They are internally regulated. Notice the 5 round holes and the ends of the 3 triangle shaped mounting screws inside the alternator? This is the mounting screws and cooling holes for the internal regulator. The most common failure for these was the "diode trio". Here is a link that shows the internals of the alternator with part #'s. Diode trio is part # 18. It's really easy to change and cost about $7 as opposed to $70 for a replacement alternator. The three cooling slats are for the rectifier. The diode trio mounts on the front side of the rectifier

https://www.jnelectric.com/publications/printableunits/Delco 10SI.pdf


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## Hacke (Feb 22, 2011)

https://partstore.agriculture.newho...359bf5299&sl=EN&currency=#epc::mr64457ag11304
Alternator, New Holland number: SBA185046320

Some examples of aftermarket alternators:
https://www.as-autostarter.ro/en/products/A5165
https://www.fleetalternatorstarter.com/alternator_10361.aspx

Check if there is a diode on the wiring from the "L" terminal, and if it is OK.


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## Fedup (Feb 25, 2014)

If the charge light doesn't come on with the key switch on, any other suggested tests/look for this/look for that are a waste of time. Solve that problem first.


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## maxreco (Sep 30, 2015)

Bob Driver said:


> I'm pretty sure the alternator on 1995 tractor would have an internal regulator. One of the most common alternators in use at that time was a Delco-Remy 10SI 63 amp alternator(see picture below). You can tell a 10SI by the fact that it has 3 cooling inlet slats at the back, there is only 1 large wire stud coming out the back of the alternator, and there is a large two-prong wire lead coming into the top of the housing. They are internally regulated. Notice the 5 round holes and the ends of the 3 triangle shaped mounting screws inside the alternator? This is the mounting screws and cooling holes for the internal regulator. The most common failure for these was the "diode trio". Here is a link that shows the internals of the alternator with part #'s. Diode trio is part # 18. It's really easy to change and cost about $7 as opposed to $70 for a replacement alternator. The three cooling slats are for the rectifier. The diode trio mounts on the front side of the rectifier
> 
> https://www.jnelectric.com/publications/printableunits/Delco 10SI.pdf


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## maxreco (Sep 30, 2015)

Here's a picture of the alternator. Notice that the two wires not connected (shown) and the "T" shaped plug(not shown) isn't plugged in as well. These were not plugged in when I bought the tractor 5 years ago. I have no idea why or what they do. There isn't enough placed to plug both of the loose wires.


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## Hacke (Feb 22, 2011)

This wiring is homemade and it is impossible to say what else have been done to the electrical system. You need a wiring diagram to find out how things are supposed to be and rewire according to that, or get a new wiring harness.

The T-shaped plug contains connectors for "L" and "R".
Look at the attached picture.
Edit
*****
Picture removed because of fake alternator news, on my behalf.
*****
"L" should be connected to the warning light. It is not, and that is why your warning light is not glowing.

There is a reason to why the T-shaped plug is disconnected. Something was malfunctioning and the easy way was to bypass parts of the system. Maybe it is a hint that the engine stops when you disconnect the battery. That points to that there is a shut-off solenoid.
I would not recommend you to reconnect the plug.


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## maxreco (Sep 30, 2015)

Hacke said:


> This wiring is homemade and it is impossible to say what else have been done to the electrical system. You need a wiring diagram to find out how things are supposed to be and rewire according to that, or get a new wiring harness.
> 
> The T-shaped plug contains connectors for "L" and "R".
> Look at the attached picture.
> ...


Thank you Hacke! Your explanation is helpful. What is the "R" spade for? (what relay?), and what does "W" (AC for the tachometer) do? As I have a mechanical tach I don't understand what this is for. Thanks again for helping to fill my empty cup of knowledge!


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## Hacke (Feb 22, 2011)

I do not know about the "R" terminal's function in this case. I only know that the "R" stands for "Relay", and that the terminal has an oscillating voltage output. Therefore it can be used for a tachometer, but there are other gizmos that can be driven from it. Or it is not used at all.
Edit
*****
R can also be the same as IG, at least on japanese alternators. This is a Mitsubishi type, the same "R" function can be found on a Hitachi type, for instance. This is a japanese tractor, after all.
*****

"W" is connected to one phase in the alternator, before rectifying. The terminal has therefore an alternating voltage that can be used for counting the revolutions in a tachometer. Not needed if you have a cable driven tachometer.
Edit
*****
I think I am wrong here also. Probably an "F" terminal, used for testing purposes.
*****

The manufacturers often put all the terminals on one model of alternator needed to suit the systems in different type of vehicles. That way they will have less models to deal with. But, it can be confusing when you have terminals that are of no use. A wiring diagram will explain the situation, though.

There has most certainly been a connection to the "L" terminal on your alternator, in order to excite the alternator and make the charging light work. The alternator is charging, but not that good, as I understand? You can start the tractor normally, without draining the battery? If so, that means that there is a magnetic field in the alternator enough to start the charging, without excitation via the charging light. What voltage do you have?
Edit
*****
Wrong.
The alternator is excited via the R (or IG terminal), the warning light is only for warning.
*****

Anyhow, you need to get the system fixed.


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## maxreco (Sep 30, 2015)

I completely agree, Hacke! Fixing the charging light is my priority. My schedule is full until next week, but I now have a good list of readings to take and things to check. I appreciate yours and all other help, this forum is fantastic!

I have the wiring diagram from the maintenance manual, which isn't great. It shows the general layout, but doesn't give details enough to identify a specific wire. If you or anyone knows of a more detailed diagram, please send a link.


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## Hacke (Feb 22, 2011)

Do not follow anything I wrote. I have found some wiring diagrams, not the best but I can see that the alternator terminal "R" on the website is like an "IG" terminal. Obviously, "R" can mean two things, clear as mud. Well, it make things easier to understand. I will come back with some sort of explanation.


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## Hacke (Feb 22, 2011)

So, let us see if I have got something right.

I have tried to interpret the (parts of) diagrams I have got. See attached picture.
Only the wiring starting at the key switch required for the charging system is in there.
"ACC" will have battery (+) when you turn the key to accessory position (lights, horn etc.).
There may be other contact configurations on your tractor and there will be splices on the wires, that do not really relate to the charging system.
I am pretty sure about the wire colouring, but I put question marks to be safe.

In your picture, there seems to be one white wire and one white with blue stripe hanging loose at the alternator. Those colours are correct, if I have got the right colours. Could this harness be the correct one, perhaps?
If so, are these wires connected according to my diagram?
What are the wires from your T-shaped plug connected to?
Maybe the loose terminals should be connected to the T-shaped plug, or it's harness?

Start like this:
Make sure the loose terminals are not touching anything.
Check all your fuses and connections.
Put the key swith to "ACC".
Is the warning light glowing when you touch the terminal on the white wire to the alternator housing (ground)?
Do you have battery voltage between the terminal on the white/blue wire and ground?

If no, trace the wires you have and compare them to the diagram.
If you find the diode, check that it is OK.

Edit
***
"Loose" was misspelled.
***

I have edited my old postings accordingly.


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## maxreco (Sep 30, 2015)

Hacke said:


> So, let us see if I have got something right.
> 
> I have tried to interpret the (parts of) diagrams I have got. See attached picture.
> Only the wiring starting at the key switch required for the charging system is in there.
> ...


Thanks! I now have a functioning indicator lamp. It glows when I am starting the engine then goes out, which I assume is the normal state when alternator is fine. Your instructions and diagram were excellent! I still plan to trace the wires and find the diode when I have more time.


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