How do you test the regulator if the alternator doesn't function.
Do you have a 2nd machine to swap the VR to?

You need to test the stator output.
Disconnect it from the VR.
Measure the AC output from the 2 stator leads at high engine speed.
Depending on which system you have, you should have an approx. max voltage at high engine speed of-
35 A approx 47 VAC
20 A spec A 41 VAC
20A Spec B 57 VAC.

I have no idea how to identify the systems.

This post was edited by bill_kapaun on Fri, Feb 14, 14 at 20:53

My problem is the engine won't start. I don't have spark at the plugs. What ohm reading should the coil be?

From the ONAN manual-

Place a black lead on negative (-) coil terminal and red lead to positive (+) coil terminal.
Primary resistance should read between 2.90-3.60 ohms.

Place ohmmeter leads inside of spark plug cable holes.
Secondary resistance should read between 14,500-19,800 ohms.

If either of the above resistances are not within specification, replace coil.

existing coil has .3 ohms between + and -. 16,000 ohms on spark plug cable holes. New coil has 3.3 ohms and 20,400. Still no spark. Control module? Tractor M# M00318X425401 Do you have a wiring schematic?

Nope. just getting my info from an ONAN manual.

This is a bit garbled since I'm copying it from a 2 column pdf file-
3. Pull spark plug wires off spark plugs and remove
spark plugs. Connect an approved spark tester to
each of the spark plug wiresand ground them away
from spark plug hole. Turn key on and crank engine
over for 5 seconds while watching for spark. If a
spark occurs regularly, the problem is not in the
ignition system. If no spark occurs, go to step 4.

Incorrect wiring can cause elec- tronic ignition damage. Do not
attach any lead or jumper with power (such as B+)
to coil negative terminal.

4. Connect a jumper lead directly from the positive
battery terminal to the positive (+) coil terminal
(smaller diameter of the two threaded posts). Crank
engine over while watching for spark. If spark
occurs, the problem is in the low oil pressure cut out
switch (if equipped) or related wiring, the lubricating
system (low oil pressure), or in the other circuitry
bringing voltage to the coil. If no spark occurs, go to
step 5.
5. Connect positive side of voltmeter to negative (-)
coil terminal (larger diameter of the two threaded
posts) and negative side of voltmeter to engine
ground. Turn key on and rotate flywheel slowly by
hand while observing voltmeter. Voltage should
switch between battery voltage and 1-1.5 for each
revolution. If voltage does not switch properly,
replace ignition module.
6. Install spark plugs and wires. If ignition module is
being replaced, be sure to connect red lead from
new ignition module to positive (+)terminal of coil,
black lead from module to negative (-) terminal of
coil.

Continuity Test
1. Pull spark plug wires off spark plugs and remove
spark plugs.
1-1 Accidentalstarting of the engine
AWARNING can result in severe personal
injury or death. Remove spark plugs before
proceeding.
2. Turn ignition on.
3. Connect a voltmeter between the negative (-) coil
terminal (larger diameter of the two threaded posts)
and a good engine ground.
4. Rotate the flywheel slowly by hand in the clockwise
direction until the voltmeter reading switches from
approximately 1 volt to battery voltage. Atthis point,
one of the chaff screen screws should lie between
the two timing marks on the blower housing. To
recheck timing, the flywheel must be rotated another
complete revolution in the clockwise direction.
Moving the flywheel back and forth across the
reference timing mark will not activate the electronic
ignition control.

This post was edited by bill_kapaun on Mon, Feb 17, 14 at 20:17

Upon further review.... I had the wires backwards on the + and - terminals of the new coil. It's firing fine now. I am charged a time out and have no challenges left. Thanks Bill for your help.

Glad it's working!

What wires go where on the new voltage regulators? The original one has two connections in the center, one over the other plus the third. The new VR has three connections in a row just off center. Which two connections are for the stator? Sterns part #435-175 replaces Onan 191-1748/191

According to my "picture" in the ONAN pdf, the center is the battery.

Thanks.

I have a 318 with power to coll but not to plugs.

Replaced coll and still no juice to plugs