Charging Problems on MF135

[Keoke]

Bigboy, a real nice job on the wiring up a 10/12 si 'Delco. If I may, I would like to share some ideas with you.

1. The number 2 terminal on alt (sensor wire) should go directly to battery pos cable at starter solenoid or relay. This would give the voltage regulator a much better picture of battery voltage thus a chg rate more tailored to battery strength. There is no problem in keeping this wire hot at all times. Original OEM Delcos were wired this way. Later, to save bucks, they simply short looped this #2 wire to to the 1/4 stud output terminal as a battery sensor wire.
This was not a good idea because now VR unit is looking at a high alt voltage and telling alt to chg low thinking the battery is at high strength. It is always better to have a VR look at true battery voltage rather then the assorted hi/low voltages found a different points in the charging circuit.

2. If you put a #53 bult in an insulated socket (two wire, non gnd so that bulb is in series) as in the OEM vehicles, you can then have a charging light built into your charging circuit. This bulb would wired in parallel to your 10 ohm resitor. Exciter current will now flow through bulb (on) and resistor. You can buy this socket with lens at NAPA or other supply houses. This bulb is put out when the diode trio in alt back feeds terminal 1 putting a positive voltage on backside of bulb that matches the pos ignition sw voltage.

3. Single wire Delco's rely on a very weak field to start charging (exciter current). This is the cause for the very low parasite drain when not not running. This means on some of these units you may have to speed up engine RPM to get charging system going. Once they start, diode trio will provide exciter current and alt will be just fine.
Also, the VR on single wire systems do vary the charge rate according to the voltage it sees at the 1/4 inch alt output stud.

cheers,

 

[BigBoyinMS]

Hey Keoke,
Thanks for adding the extra info. I was actually just putting out a quick and very basic diagram for anyone to use but it seems some want to argue 1-wire is better and nitpick the rest of it. I might take time later to add all the extra info and explain all the whys for the nitpickers but for now I figure the ones that want to use it will.

 

[Keoke]

Bigboy, in terms of a quick, easy and cheap the one wire 10si alternator is perhaps a better way to go.
However, the downside of this installation compared to your 3 wire system is:

1. There is no feed line for exciter current to field only when ignition is on. Consequently, there is no way to wire a charge light into the circuit. Since some tractors already have a charge light OEM installed you are then giving up something to make the swap.
The 10 ohm resistor in parallel to lamp is to insure that if bulb burns out you will still get exciter current to alt through resistor. All 10si voltage regulators have a very small parasite drain(under 75ma). In single wire units, in addition to this VR draw, a trickle current is added to the field winding to give at least a weakl magnetized field for charge startup. The SI alternators have no pernament magnets so electro magnetism must be created. This exciter current is taken out of the 10 gauge output wire and varies by who does the alt conversion.
By the way oldtimers, dc generators had pernament magnets installed so you could push start these vehicles when battery was completly dead and still fire engine up. Those days are gone now.

2. As mentioned earlier, the highest voltage found in any charging circuit is at the alt output terminal. Having a VR take it's battery sensing info at this point will result in a lower charging amp rate to battery/load. E.G., with 30 amps flowing, voltage at alt post could be 14.8 while at battery it's at 13.8 volts, if VR unit saw the 13.8 number it would call for more amps from alt then if it saw the higher 14.8 number at the alt output terminal.

3. If an ignition switch has a terminal marked "accessory" then there is no need for an isolation diode to prevent igniton feedback and after running. With ignition key off their is no connection from igniton to accessory terminal. In this case move terminal 1 (exciter) wire to the accessory terminal and leave out diode.

4. An example of voltage regulators setting charging rates by what they see are motor homes with separate batteries that are in parallel when vehicle is running but separted when stopped. When running the voltage regulator is always looking at the higher (truck) of the two battery voltages and setting the charge rate accordingly. Consequently, the RV battery, which may be weak from use, will be charged low because the VR unit does not see it's weakend condition and instead is basing it's charge rate on the vehicles battery condition. Ironically, if both batteries (weak and strong) were hooked in parallel, with engine off, the strong one will charge the weak one until an equal voltage balance between the two is reached. This however, will take a long time.

cheers,

 

[dqdave1]

Big boy; Please do not take offense to questions raised about one wire vs. 3 wire. I was not nitpicking. You are correct that a 3 wire system is better. All new auto manufactorers use 3 wire systems today as well as tractor makers. My point was that older tractor owners that are rewiring from generator systems to an alternator system usually want the easiest route and the one wire system is quick, cheap and simple.

 

[wsw483]

I have a similar problem. My MF135 has an alternator. I hooked a multi-meter to the back of the alternator.(Red lead to the large bolt where the battery cable is attached and black lead to the frame.) It shows that it is putting out about 15.5 volts. I then hooked the meter to the battery. With the engine not running it read 11.8 volts. With the engine running at any speed it read the same. The volt gauge on the tractor is not showing any charge taking place. How can I tell if my voltage regulator is bad??? Is this most likely my problem.??? What do I need to check and do you have any ideas??? Thanks.