310-8 voltage regulator

[hm12460 53]

I decided to get my 310-8 out today and get it ready for spring. Sharpened up the blades, put the deck on, put the trac-vac on, changed the oil in both. Fired the old toad up and i noticed the installed voltmeter showing 16 volts?! This cannot be. Didn't do that last time i ran it. So i got out my trusty digital multimeter and with the engine running full throttle, it was showing 15.85 volts. Not good at all. After a close inspection of things I came to the conclusion that I couldn't find the voltage regulator. Looked at a parts diagram on Partstree.com and they don't list one for a 1986 310-8. Whats up with this?? All my John Deere's (110-216) always had one. I never heard of such a thing. Anybody got any words of wisdom?

[rmaynard 16,404]

The 310-8 does not have a regulator as such. The DC voltage is provided by a simple half-wave rectifier circuit, which uses a single diode in one of the AC wires coming from the stator. Since the diode only allows current to move in one direction, half of the AC voltage, which in the case of the varying AC voltage from the stator, is clipped in half and appears as anywhere from about 1 to 16 volts DC, depending upon how fast the engine is running.

As with any electrical circuit, check to be sure that all grounds are good, and that all other connections in the circuit are as well.

[hm12460 53]

Rmaynard, ac voltage should be right around 30, so 1/2 that would be 15. Isn't that a bit much? I'd rather see it around 14 or so. I did check all the grounds and they appeared to be clean and tight. Thanks for your reply!

[rmaynard 16,404]

It would only be 15 volts if the engine is running at full speed. Since it is rare that you run at full speed all the time, the average voltage will be lower.

[Duff 206]

If you're worried about boiling your battery, just run with the lights on. It should use up some of the extra juice. The 310-8 only puts out either 1.25 or 3 amps depending on which stator configuration the engine was built with.

Duff :thumbs:

[Save Old Iron 1,571]

2 quick comments.

Its highly unlikely the charging system changed sitting over the winter but it is likely the battery did.

I would perform a load test on the battery to check the capacity, I am guessing you have a sulpahted battery from non use over the winter. The charging system now finds it too easy to charge the sulphated battery and even with limited charge current can easily and quickly over voltage the battery.

Test this theory by intentionally DISCHARGING the battery and then allowing the tractor to charge the battery. A battery that is absorbing charge current will not allow the charger to reach its peak voltage for a few hours. During this charge cycle, the voltmeter should read lower than 14 volts.

If the charge system has been modified with a new / different stator, it is possible the charge VOLTAGE is a little higher than desired. In this case, inserting additional diode(s) in line with the original charge diode will lower the peak charge voltage. Peak charge VOLTAGE will be lowered by approximately 0.7 volts for every diode inserted in series with the original. Use 100 volts rated diodes, 3 amp or greater. Available at a Radio Shack near you.

The fact you would have to insert 2 diodes to lower the voltage to 14.5 volts tells me you most likely have a battery issue.

[hm12460 53]

Gentlemen, thank you for your expertise. SOI, your comments make a lot of sense to me. I put in a new battery about 2 weeks ago. After the install it started up fine and i honestly don't remember checking the installed voltmeter. Defective battery possibly?

[Save Old Iron 1,571]

Harold,

I should have asked what charging system you have on the 310. I have recently developed a nasty habit of responding to posts too late at night - right before bed time.

If you have the limited 3 amp or less charging system that Duff suggested, all my previous comments are correct. I do know some 312's have this system but I do not have any real world knowledge of the 310's.

Let us know if you are dealing with a 15 amp system or the 3 amp charge system.

If you have the standard finned aluminum regulator (15 amp) then we are either looking at a defective voltage regulator or more likely, corrosion in the ground path to the regulator case. If you have the 15 amp system with the three prong regulator, run a quick ground wire from the bolts on the regulator case directly to the battery ground.

If the voltage decreases to normal levels with the jumper in place, check all the ground connections thru the many interconnected body panels up the regulator. Rusty body panels , bolt holes, bolts, quick clips can all cause a poor connection between the regulator case and the battery negative terminal .

[hm12460 53]

Hello Chuck, again, thank you for your help. I'm quite certain my charging system is way less than 15 amps. 3 amps as Duff has stated sounds about right. I do not have an electric pto or lift. My tractor does not have a voltage regulator, thats what is making this so difficult for me. I never saw such a set up! I did swap in a different battery to eliminate that as my problem, and the running voltage did not change. So my new battery should not be the cause. Am i going to cook my battery running 15.85 volts at full rpm? I generally run it 3/4 to full throttle. It's not a real good idea to let a splash lubricated Kohler run at a lower rpm.

[TT-(Moderator) 1,162]

Some good reading/info:

http://www.wheelhorseforum.com/index.php?showtopic=20049

[Save Old Iron 1,571]

If you are handy with a soldering iron,

grab a pack of

3-Amp Diodes

Model:

1N5402

Catalog #: 276-1143

from Radio Shack.

Here is your original configuration

Cut back a section of the insulation around the current diode and insert 2 additional diodes in series with the original. Solder the connection(s) and re-insulate with heat shrink or electrical tape if no shrink is available. Please note - the additional two diodes must be wired with the cathode "band" on the diode body oriented in the same direction as the original diode.

The final configuration should be

Remember each additional diode will drop between 0.6 to 0.7 volts of the charge voltage. This voltage drop will remain constant thru the entire RPM range of the engine.

I do know there have been "kits" available from Briggs to address this issue. I have not seen any solid evidence of the kit contents. Given the low cost of the kit and the small physical size of the kit, I'd bet my lunch money it was similar to my drawing above.

[hm12460 53]

Terry, thanks for posting that link, it helped me out considerably. I may not have a problem either, will find out soon enough. Chuck, i thought i was a pretty good automotive electrician, but now i know better! I also thought of installing a switch to interrupt the flow of electricity to the battery to prevent over charging it, but that would run the risk of damaging the engine stator. I like the idea of adding diode's! If i do indeed have an issue here, that will be my solution. I thank you gentlemen tremendously for your help, i learned something new today!

[Save Old Iron 1,571]

Harold,

I have been tossing around an idea for a 3 amp regulator assembly made from LM350 three terminal regulator chips. This design would be the ultimate fix for those operators who also expect the charging system to keep the battery topped off at idle.

Register at SOI University

http://saveoldiron.47.forumer.com/

if you are interested.

[markbenz 0]

Folks

 

Just put a new Odyssey pc680 battery into my WH B-111. Started fine two or three times over about 40 mins. Then nothing. Voltage at battery showed 12.3v so assumed some lockout problem. 30 mins later voltage at battery showed 10.7v with engine off. Has my mower killed my new battery? I put the old battery( two years old only measuring 9.98v) back in and jump started the mower and measured 20.8volts across the battery with engine at full speed, 14.5v at low speed. Have I a diode or regulator problem? Appreciate your thoughts and input.