jst1more 40 #1 Posted May 22, 2016 My daily worker is a 1973 Auto 12, and when I engage the electric pto, I have only have 11/2 hours of run time until the battery is fully discharged. This weekend, I researched previous forum discussions on charging system problems and I started with testing my stator . Ohms check out at .2 and when i disconnect the two leads from the regulator and opened up the rpms the AC volts bounced all over the place- i was hoping to see a consistant reading of around 30 volts. I removed the stator and headed to the mower shop to price a new one. The owner of the shop thought that the stator looked good- he told me that when a stator goes bad you will see evidence showing that the coils have heating up. The owner hated to see me order a new stator when he thought the problem might be in the flywheel. I went home and checked the flywheels magnets, they all seemed to be secure and in place. My questions are, can the magnets be too weak to produce a charge? Can a stator go bad without showing any abnormal signs? What should I check or what might I have overlooked in terms of testing my stator? Thanks Scott . Share this post Link to post Share on other sites
squonk 38,569 #2 Posted May 22, 2016 What kind of meter are you using? I have seen real good meters as well as the cheapies read all over the place if their digital. Any chance you can get your hands on an analog meter and take a reading. I doubt the flywheel magnets are the problem. I would bet on the regulator or poor connections. Read my post if you haven't allready. Share this post Link to post Share on other sites
Tuneup 1,412 #3 Posted May 22, 2016 Ditto - quality of the meter. You don't have a beautiful sine wave coming out of the stator so readings can be erratic. Not much to the stator and the regulator provides a stabilizing load. Monitor the output of the regulator with throttle and check the connections. Mine were toast - with the DC output hanging by a thread. Share this post Link to post Share on other sites
jst1more 40 #4 Posted May 22, 2016 Thanks guys, I never thought about my digital meter being the culprit. I will look into getting my hands on an analog meter and I will also double check all my connection. I even ran a ground wire from the regulator thinking that might be the problem. If the stator checks out then can the ignition switch also become part of the charging problem? Share this post Link to post Share on other sites
squonk 38,569 #5 Posted May 22, 2016 Tractor Supply sells a cheap analog meter for $15.00. As far as the switch goes, anywhere there's a connection can be your culprit. Share this post Link to post Share on other sites
Save Old Iron 1,563 #6 Posted May 24, 2016 (edited) On 5/22/2016 at 6:50 AM, Tuneup said: You don't have a beautiful sine wave coming out of the stator I don't know what a "beautiful" sine wave looks like but here is what the stator output (bottom trace) and points side voltage trace (upper trace) look like on an average WH charge / ignition system (thanks Mark!). No unusually high crest factors here, the quality is good enough for a tachometer to register correct RPM's on a 520. So long as the users meter is not defective, we should see a steady reading. On 5/22/2016 at 8:14 AM, jst1more said: Thanks guys, I never thought about my digital meter being the culprit. I don't believe we ever asked what brand / model of meter you were using. If you set it to AC Volts and measure a wall outlet in your home, you should see a steady 115 to 120 VAC. Some less expensive meters are poorly shielded against radio frequencies - such as the radiation interference from a solid core spark plug wire. Edited May 24, 2016 by Save Old Iron 2 Share this post Link to post Share on other sites
squonk 38,569 #7 Posted May 24, 2016 (edited) I can put my fluke meter on those Stator wires and get that erratic reading. If I put my Simpson analog on it, nice and steady. Edited May 24, 2016 by squonk Share this post Link to post Share on other sites
Save Old Iron 1,563 #8 Posted May 24, 2016 5 hours ago, Save Old Iron said: Some less expensive meters are poorly shielded against radio frequencies - such as the radiation interference from a solid core spark plug wire. If the AC Volt functions OK with the wall socket test, try twisting the meter leads into a braid, place the meter on the ground as far from the spark plug / wire as possible and take the readings again. The meter leads are most likely acting as an antenna and the spark plug wire as a broadcast station (very similar to the interference picked up by an AM radio when held near a fluorescent light). I use Fluke 87 III meters routinely and have not noticed any interference issues when checking open stator leads - I always lay my meter on the ground and not on the engine tins or near the ignition system.. At full throttle, the spark plug fires 60 times per second and the stator design produces 18 AC cycles per spark - so the stator is about 1000 to 1100 HZ - well within the capability of a decent digital meter. 2 Share this post Link to post Share on other sites
Save Old Iron 1,563 #9 Posted May 24, 2016 spark plug wires are such good antenna that you can use them to read engine rpm 1 Share this post Link to post Share on other sites
Tuneup 1,412 #10 Posted May 24, 2016 Agilent - sweet scope. My old 1742 with the DMM atop takes me back to when our tech, Anna, calibrated and tuned the time control. Ah, the 80s, HP, and the leftover tech center stuff on the bench... Keysight's not quite the same. Share this post Link to post Share on other sites
jst1more 40 #11 Posted May 25, 2016 Well after reading more post and learning a little more ( you guys are great) I found the problem. I realized with the key in the on position that the rectifier B+ terminal was showing no volts. That led me to search the forum about ignition switches, which led me to NAPA to buy a $15.00, part # 7-01854, ignition switch. After scratching my head a bit to get the switch wired correctly, I turned the key and the system is charging. This was a great learning experience for me, thanks all 1 Share this post Link to post Share on other sites
Tuneup 1,412 #12 Posted June 1, 2016 Excellent - congratulations! Electrical gremlins are the worst and you got past it cheap! Share this post Link to post Share on other sites