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18HP B&S charging circuit question (no charge)


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08-03-14, 01:39 PM   #1  
18HP B&S charging circuit question (no charge)

Howdy folks!

I recently fell into a deal on a great condition Bolens tractor model 1668.

The catch, of course, is that it needs some tinkering. The governor supposedly doesnt work (not that I can tell with just the mower deck) and the battery doesnt charge.

Since I intend to use the snow thrower this season, I'd like to get these two problems sorted out- starting with the charging circuit, since it's a pain for me to keep topping up the battery!

I've got a pretty fancy service manual I've been going over, but it doesnt cover much on the charging system. From what I can gather, there's some sort of copper coil under the flywheel- and the flywheel has magnets in it. This means there's a wire that comes out from under the flywheel somewhere.

I did find a small black wire on top of the engine that looks out of place, connected to a red wire that runs into the cluster. Hooked up an analog voltmeter to it while the thing was running, and its flat- no AC or DC. Not sure if its the right wire.

https://dl.dropboxusercontent.com/u/...2016.15.27.jpg

Generally, my next step would be to pull the flywheel and see what there is to see- but it looks like the only good way to do that is to pull the whole engine out, so I was hoping to maybe get a little insight from someone more familiar with this engine before I go digging too deeply.

Any thoughts? Does this wire look suspect, or am I barking up the wrong tree?

 
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08-03-14, 01:53 PM   #2  
UPDATE

Curious me couldnt keep my hands off of it. Went looking and found a second wire coming out of that same cover, on the other side.
Remembering that a copper coil and a magnet makes a pulse, I decided to see if there was any AC current between these two wires.

Surprise, there is!
About 8V at idle, and what looked like 15V at high RPM- I assume this is good news, since we're getting charging voltages at running speed at least- its just in AC and not DC, and its not getting back to the battery.
I presume there's some sort of dohicky between here and there that's the culprit- but I'm not the first one to have my fingers in these wires.

 
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08-03-14, 02:10 PM   #3  
update 2

Found a charging diagram. Looks like the things between this generator (stator?) and the battery are:

Diode
Ignition Switch
Ammeter
Circuit breaker
Solenoid

The Amp meter is interesting- it goes from 0 when off to a negative 10 or so with lights or the engine running. This tells me that the circuit doesnt have a break in it.
Going to try and find this diode. If they work anything like I suspect they do, power should flow one way and not the other...

 
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08-03-14, 03:57 PM   #4  
Another update!

Now I'm in over my head.

So, I took a look at the "other" engine that came with this thing, and it had a part this engine did not- a rectifier. So I cut back into the wiring harness a bit and found that somebody at some point decided they needed more wires than they had.
I've now taken it pretty much apart, wiring wise, and need some info to put it back together correctly.

https://dl.dropboxusercontent.com/u/...ens/wiring.jpg

1 and 3 are the two lines for AC on the rectifier that I stole off a different engine (this might be the wrong kind?)
2 is the charging wire, which conveniently clipped to a line that had previously been wired to 4 (feeding one leg of AC into the DC system- classy!)
4 and 5 are the two small black wires that I believe go to the rectifier. They get AC across them, less at idle and more at high RPM.
6 is a metal tab that doesnt appear to go anywhere, electrically. Both 5 and 7 were connected to this when I got it.
7 is a dark blue wire that goes to the ignition switch, and has something to do with turning the engine off.

Now- Right now, with the engine off, both stator wires (4 and 5) measure as GROUNDED.
If I start the thing up with 7 disconnected, it wont turn off- but if I connect 7 to 5 it turns off with the key as expected. (This is how it came)

Now logically, in my mind, 1 should be wired to 4, and 3 should be wired to 5- connecting the stator leads to the rectifier. If I do this, it will not start. (crank but no fire)
If I connect 1 to 4 and 2 to the red wire, it seems to read 0 on the amp meter when running, slightly less with the lights on. This to me implies its getting some power, but not enough.

Questions-
Dark blue. Should this be grounded, or what?

Are the rectifiers different for different engines? This is an 18HP engine, the rectifier was on a 16HP model that looks identical to me- although the 18 doesn't seem to have mounting holes for the rectifier.

What's up with 6? Best I can tell it exists just to connect two other things together, and is not connected to anything on its own.

Probably more to follow, need to have a pint and clear my mind

 
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08-03-14, 06:58 PM   #5  
I can't tell what all wires are shown, but on the voltage regulator, the two yellow wires should connect to the two wires coming out of the charging stator. The red wire should go to battery positive, often through the ammeter and to the positive post on the keyswitch when the key is on.


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08-03-14, 08:54 PM   #6  
Thanks Cheese!
Unfortunately as noted in my last post, the stator wires are 4 and 5- and when connected to the two yellow wires of the rectifier, the engine doesn't start.
Still trying to work that one out, since it starts fine with them connected to nothing!

 
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08-04-14, 01:26 AM   #7  
If so, one of the wires you are connecting is going to the coil I would guess.


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08-04-14, 09:57 AM   #8  
Afraid I don't follow-
When you say the coil, are you referring to the stator? In that case, I'm fairly certain that both of these black wires go there. If I connect them both to the yellow wires of the rectifier, it won't start- but it starts fine with the stator disconnected from everything.

The only thing I can think of is the rectifier is charging the chassis making the spark plugs not fire- but to manage that I'd think it would need to be charging it with spark voltage, not stator or battery voltage.

Hoping to take a closer look after work tonight, but I'll only have a couple hours of daylight- trying to get an idea of what to spend my time on.

 
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08-04-14, 10:06 AM   #9  
Ignition coil.
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08-04-14, 11:58 AM   #10  
Ahh, I follow now. If that wire goes to the coil, then that would explain why it was attached to that nub- and why the blue wire for turning it off was connected to it.

That does, however, mean I'm missing a wire for the stator.
Guess the next step is to pull the engine so I can get under that flywheel and see what's going on.

thanks!

 
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08-04-14, 04:37 PM   #11  
Check voltage from the single stator wire to ground. Both AC and DC.


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08-04-14, 05:00 PM   #12  
That might have been clever- instead I pulled the engine, pulled the flywheel, and found that the stator only has one wire.

I had checked AC on that wire and got about 8v or so at idle and probably close to 15 at high rpm- I didn't think to check DC.

I found an engine model number- 422437
did a lookup and I see that there are single and dual wire stators- so I've gotten myself in over my head now

Anyhow just got some bad news from a friend so I need to go sort that out. Might get some time tomorrow to read up more on how these things work.

 
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08-04-14, 05:18 PM   #13  
Ouch... once you get it all back together and back on the mower, check for DC voltage at full throttle from that wire to ground.


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08-05-14, 05:45 AM   #14  
A thought I had overnight- the rest of the mower is set up to use a two-wire stator. This engine was available with both one and two wire stators- and I have a 16HP engine (that came off the mower, and looks identical) that has a two-wire stator and a bad valve.
What are the chances I can just bolt the two-wire stator on and have it work with this flywheel/engine?
If I could, the rest of the wiring is already in place to hook it up and go.

 
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08-05-14, 09:09 AM   #15  
It looks like this engine was available with a "dc only" single wire, and a "dual circuit" two wire, as well as some higher amp ones available.
It looks like these are fairly generic, so I'm going to move forward with the idea of stealing the stator from the other engine. If it bolts on, my guess is it'll work.

 
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08-05-14, 09:25 AM   #16  
I would have probably opted for the single wire system. Less to worry with and your harness is set up for either, but the idea of switching it over will work,, assuming the other stator and regulator work.


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08-05-14, 09:28 AM   #17  
Is the diameter of the two flywheels so similar on the 16hp vs the 18hp that the arc of the alternator is close enough that it may still work? I know that has held true for the magnetos on some slightly smaller Briggs engines, 10 and 12 HPs.

 
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08-05-14, 10:13 AM   #18  
One way to find out. The engines look identical from a glance, but I've not gotten very close to the smaller 16hp unit to see.
If it's a bolt-on, my guess is its the same size and flywheel.

Question- I didn't notice a key for this flywheel when I took it off. I didn't think to mark its orientation with the shaft- did I just screw myself over on reassembly?

 
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08-05-14, 05:41 PM   #19  
Well, the two-wire stator bolted right up- they look identical other than the number of wires.

Got the thing back together, seems at full throttle its putting out somewhere around 15-20VAC.

Feed that into the regulator, which puts out... exactly nothing!

Guess I should have looked into converting the rest of the system for single wire instead

Safe to assume the regulator is toast? does 15VAC sound about right for a dual wire stator?

 
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08-05-14, 06:39 PM   #20  
That's exactly why I would have preferred the single wire non-regulated setup.

15 vac is not what I would want to see. More like 28 or 30.


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08-05-14, 08:18 PM   #21  
I can't seem to find specifications in the service manual, but I have found a couple threads around the internet referencing this model tractor (which the stator is off of) saying it's at 15 VAC or so, and that isn't their problem.

Bolens 1600 Hydro Eliminator - MyTractorForum.com - The Friendliest Tractor Forum and Best Place for Tractor Information

Where the heck are the spec sheets on these things?
I've finally dug up the heat shielding which has the model number for the engine this stator is off of- B&S 402437

http://www.briggsandstratton.com/us/...ifications.pdf
Page 19 here shows the closest I can find to what I have- and shows that 20vac is right on the money. I'm tempted to bite the bullet and buy a cheap voltage regulator.

 
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08-06-14, 01:21 AM   #22  
I don't know which alternator is on that engine, but I would think it is a 16 amp or better. That page you linked to shows a 16 amp regulated alternator putting out 30 volts AC. You can probably expect 15 volts per leg and that may be what they are measuring in the other forums you're visiting.

Page 19 on that link you showed is a stator for a tiny little briggs engine smaller than a gallon of milk. You have a bigger engine, bigger stator, more amps. Page 22 will show something more like what you have.


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08-06-14, 06:40 AM   #23  
Thanks again!
Looking at 22, it does look about right- not sure how I missed that one before.
Looks like there are three versions of that coil, though, and two of them are 20V. I ordered in a $20 regulator last night- my brother has the same tractor, so if it turns out to not be the fix the spare wont be a total loss.

Looking at the pictures I took, it looks like it was drawing more than 15A off the battery with everything running- so I have to figure it probably isn't a 13a coil. The only ones I'm seeing any bigger than that should be closer to 30VAC across the two wires, as you stated.

Real shame none of these parts have numbers stamped on them- I hate this guessing game.

Can someone give me a quick rundown on how a single wire stator works? Is it just fed through some sort of diode to pull DC, or does that also need some sort of regulator?

 
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08-06-14, 09:34 AM   #24  
It has a diode already in the output wire and it just connects directly to the wire on the mower that your regulator connects to on the other style setup.


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08-09-14, 09:01 PM   #25  
Well, the new inverter doodad should be here monday.
In the mean time, I checked out my brothers Bolens (tecumseh engine) and his coil does put out ~35VAC- but one thing I did notice is the wires coming out of his coil were *way* thicker than my own. Here's hoping mine was built for 20VAC!

 
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