david@stearnsfarmsinc.com 2 #1 Posted June 20, 2022 What (and where) is the recommended replacement coil for seemingly obsolete coil #166-0761 (Onan P216G-I/10538B on Wheel Horse 516-H)? Existing coil has full continuity (zero ohms) on primary coil terminal. Secondary coil terminal OK @ 19,000 ohms. Engine (sometimes) has spark and engine starts, but always dies in few minutes. Does the coil get weak? New development. I have gone through some basic testing, but willing to replace coil if appropriate one is available. Thanks! ----Dave Martin 1 Share this post Link to post Share on other sites
Achto 28,883 #2 Posted June 20, 2022 Here is one source for an aftermarket one. https://www.amazon.com/Goodbest-Ignition-541-0522-166-0761-166-0820/dp/B07BFXC9V4/ref=sr_1_2_sspa?gclid=EAIaIQobChMI1uzCraK8-AIVBhmtBh2s1wBUEAAYASAAEgKBEfD_BwE&hvadid=275846778629&hvdev=c&hvlocphy=1016367&hvnetw=g&hvqmt=e&hvrand=11065694550424553172&hvtargid=kwd-301319994866&hydadcr=5706_9590298&keywords=166-0761+coil&qid=1655736319&sr=8-2-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUFQUzJSMzVCTkMwSE8mZW5jcnlwdGVkSWQ9QTAzODExMDYyNzFKVzdWVVFJNUlRJmVuY3J5cHRlZEFkSWQ9QTA3NTA4NjgyMzZOS0JTNE9FVVRIJndpZGdldE5hbWU9c3BfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ== 3 Share this post Link to post Share on other sites
ri702bill 9,046 #3 Posted June 20, 2022 (edited) Dave - nice to see a fellow Rouge Islander here on Red Square. Welcome - plenty of good folks here that are willing to share their WH knowledge. Many may be away this upcoming weekend - they would be at the annual "Big Show" in PA. Bill Edited June 20, 2022 by ri702bill Share this post Link to post Share on other sites
Handy Don 13,395 #5 Posted June 21, 2022 (edited) 11 hours ago, david@stearnsfarmsinc.com said: Does the coil get weak? No, they don't weaken. They develop a fault, i.e. a short or break. Typical is overheating and melting the varnish that insulates the internal wiring but also shock or simply aging can damage the varnish as well. The fault can be temperature-dependent--i.e. ok when cool, short and fail when warm. It's no accident that the stock Onan coil is situated in the cooling airflow. Edited June 21, 2022 by Handy Don Share this post Link to post Share on other sites
david@stearnsfarmsinc.com 2 #6 Posted June 22, 2022 Handy Don: Interesting. Thank you! I use analog multimeter and primary terminals show no resistance (zero ohms). Is this a sign of a bad coil? Secondary OK at 19,000 ohms. I tested ignition module and that seems OK (12 volts then 1.5 v on next revolution with proper hookups, etc.). Engine compression 75 PSI each cylinder (minimum but OK) so don't think I've got a fallen valve seat (although did not do leak down test). Ignition problem. Spark plugs and wiring (grounds) cleaned and test OK, but plastic connections at wiring harness by PTO switch appear damaged (burned?). I removed, cleaned and applied dielectric grease and connections all tested OK. Engine sometimes with no start (full charge on battery) and sometimes will run only few minutes, then no spark. It seems I am down to a coil ,problem, but want to make sure I get a good replacement with proper ohm readings and for engine with ignition module (ie, no points). I am not sure you get what you need on the internet. Sorry for this long narrative, but I am determined to get this tractor working!! Any thoughts? Thanks again. P.S. Tractor bought new by family. ---Dave Martin Share this post Link to post Share on other sites
Jeff-C175 7,204 #7 Posted June 22, 2022 51 minutes ago, david@stearnsfarmsinc.com said: analog multimeter and primary terminals show no resistance (zero ohms). Is this a sign of a bad coil? The primary of the coil will be a low resistance, somewhere around 3 - 6 Ohms or so. Make sure you are using the R x 1 scale on your meter. It's sometimes difficult to tell the difference between a SHORTED primary, and the correct resistance. 1 Share this post Link to post Share on other sites
david@stearnsfarmsinc.com 2 #8 Posted June 22, 2022 Jeff: Thanks for your reply. I used the Rx1 scale and confirmed primary is flat-out zero. I understand it should be 3 - 6 ohm. Does "zero" generally confirm a bad coil? As mentioned, ignition module checks out to specs and wiring/grounds seem OK. And where oh where can I get a reliable coil for this engine (Onan P216G-I #10538B)?! Original coil (#166-0761) seemingly "obsolete". Thanks! ---Dave Martin Share this post Link to post Share on other sites
pacer 3,176 #9 Posted June 22, 2022 Whats the problem with the Amazon coil link shown earlier?? I just ordered one for my B43M Onan (looks identical to the one shown) and its running happily along. I had a totally different reason for needing a new coil --- I left the key on!!! Share this post Link to post Share on other sites
lynnmor 7,609 #10 Posted June 22, 2022 When checking the coil, be sure that the condenser and everything else is disconnected. Check the condenser to see if it is shorted. The coil should read 2.90 to 3.60 and 14,500 to 19,800. I have used the cheap coil kits from eBay with no problems. A loose valve seat can still have reasonable compression since the seat will be held against its bottom surface. At 75 psi, I would be popping the heads to see what needs repaired, often refreshing the valves and seats will restore the compression. If a valve is leaking that can lead to a hot seat and eventual failure. 1 Share this post Link to post Share on other sites
Jeff-C175 7,204 #11 Posted June 22, 2022 6 hours ago, david@stearnsfarmsinc.com said: Does "zero" generally confirm a bad coil? Before you measured the coil, you held the two probes together and used the 'zero' function on your analog meter to be sure that zero was really zero? Just checking because on the Rx1 scale you can have a fair amount of 'offset' on the reading if you don't perform that step first. If the primary is indeed SHORTED... aka "ZERO" ohms, then yes, it would be bad. BUT ... 2 hours ago, lynnmor said: When checking the coil, be sure that the condenser and everything else is disconnected. Check the condenser to see if it is shorted. Share this post Link to post Share on other sites
Jeff-C175 7,204 #12 Posted June 22, 2022 4 hours ago, pacer said: Whats the problem with the Amazon coil link shown earlier? Probably nothing... here's a shorter version of the link. https://www.amazon.com/Goodbest-Ignition-541-0522-166-0761-166-0820/dp/B07BFXC9V4/ @david@stearnsfarmsinc.com Share this post Link to post Share on other sites
david@stearnsfarmsinc.com 2 #13 Posted June 23, 2022 Wow! I am impressed with this forum (just joined - never been on a "forum" before). Quick, intelligent responses! Just for the record I am only a "hobby" engine guy, but fairly comfortable with small engines (age 81), appropriate tools (analog multimeter, etc.), most testing processes (only fair with electrical, but work my way through it - with directions...). Anyway, thanks for the input. I am today buying the new coil from Amazon as suggested. 1 Share this post Link to post Share on other sites
pacer 3,176 #14 Posted June 23, 2022 Yep, you have indeed found a forum that is ..... well, dang, its just amazing!! As youve found with your problem. these guys will sit down and go into extensive lengths trying to help diagnose a problem. And with the large membership with the amount of knowledge .... well, SOMEBODY will come up with an answer to your problem. You mentioned youre 81, well I'm 82 and over the years I have belonged to a good handful of forums and this one is just the .... well, BESTEST!! Welcome aboard!! Share this post Link to post Share on other sites
Handy Don 13,395 #15 Posted June 24, 2022 11 hours ago, david@stearnsfarmsinc.com said: Wow! I am impressed with this forum (just joined - never been on a "forum" before). Quick, intelligent responses! Just for the record I am only a "hobby" engine guy, but fairly comfortable with small engines (age 81), appropriate tools (analog multimeter, etc.), most testing processes (only fair with electrical, but work my way through it - with directions...). Anyway, thanks for the input. I am today buying the new coil from Amazon as suggested. I was offline for a day traveling and the gang has you well covered. Glad you are enjoying the forum! Share this post Link to post Share on other sites
