ignition question
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=124321
Printed Date: 19 Jul 2025 at 8:41pm
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: ignition question
Posted By: dirtfarmer
Subject: ignition question
Date Posted: 08 Jun 2016 at 7:38pm
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D17 series 2, converted to 12v (-) ground. Had a short take out some wiring, ignition switch, my coil and electronic ignition module. Replaced all of that and now it runs fine again. The only difference is that when I turn the ignition switch off, sometimes it will keep running, sometimes it will run a bit longer and stop and sometimes it stops right away. When it finally does stop I measure about 0.1 Vdc at the coil so I know the ignition switch is doing what it should be doing. The only thing I can think is the alternator is somehow feeding the coil with the ignition switch off. Can anyone shed some light on this? Here's what my wiring looks like, minus the ballast resistor and warning light.  |
Replies:
Posted By: Kurzy
Date Posted: 08 Jun 2016 at 8:07pm
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Howdy dirtfarmer, Had same problem. Currant was running back to alt draining battery. Put a diode in line # 1 by alt. Put in so currant can not run back into alt. Worked for me. Kurzy
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Posted By: dirtfarmer
Date Posted: 08 Jun 2016 at 8:11pm
| Kurzy, did that problem keep the ignition firing with the switch off? |
Posted By: DSeries4
Date Posted: 08 Jun 2016 at 8:15pm
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how long does it keep running after you turn the key off?
------------- '49 G, '54 WD45, '55 CA, '56 WD45D, '57 WD45, '58 D14, '59 D14, '60 D14, '61 D15D, '66 D15II, '66 D21II, '67 D17IV, '67 D17IVD, '67 190XTD, '73 620, '76 185, '77 175, '84 8030, '85 6080 |
Posted By: dirtfarmer
Date Posted: 08 Jun 2016 at 8:24pm
| sometimes it will stop after a few seconds, once I had to turn the fuel off. |
Posted By: Kurzy
Date Posted: 08 Jun 2016 at 8:26pm
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Howdy dirtfarmer, You should only have one wire going to coil from on-off ignition switch. Key on currant to coil, key off no currant to coil. No currant to coil no run. Kurzy
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Posted By: Gerald J.
Date Posted: 08 Jun 2016 at 8:53pm
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You need the lamp, the diode, or a resistor in that wire from the ignition circuit to the alternator. Otherwise it will feed back and keep the ignition supplied. There is one other option and that is a switch that closes on oil pressure rise (with two connections not grounded) in place of the lamp, resistor, or diode. The diode is the simplest solution. As a test, when its running after the ignition key is off, pull the plug from the alternator, it should stop immediately proving the alternator is feeding back through that wire. Another option is with a ignition switch having an accessory terminal switched separately from the ignition circuit and connect the alternator feed to that post, just never leave the switch in the separate accessory position that will run down the battery. Gerald J. |
Posted By: dirtfarmer
Date Posted: 08 Jun 2016 at 9:16pm
| I'm thinking the the diode/warning light will help me. I'll probably swap the alternator too due to paranoia. Thanks for the insight. |
Posted By: DougS
Date Posted: 08 Jun 2016 at 9:41pm
Just put a diode in as Gerald suggested. Problem solved. Another alternator would be a waste of $$$. |
dirtfarmer wrote:Posted By: Gerald J.
Date Posted: 08 Jun 2016 at 10:17pm
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I AM SURE THE DIODE or LAMP will solve your run on problem. They are there precisely because of that need. Gerald J. |
Posted By: Gary in Texas
Date Posted: 09 Jun 2016 at 3:55am
| see note 4 of your schematic. |
Posted By: jaybmiller
Date Posted: 09 Jun 2016 at 6:05am
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FYI, without the diode or 'idiot' light, the alternator will supply power to the coil ! That's what keeps it running. I've used lights and or diodes....one day I MUST get them all the same! The light I used fits into the 1/2"(?) hole in the lower left of the D-14 'dashboard'. Jay ------------- 3 D-14s,A-C forklift, B-112 Kubota BX23S lil' TOOT( The Other Orange Tractor) Never burn your bridges, unless you can walk on water |
Posted By: Kurzy
Date Posted: 09 Jun 2016 at 6:36am
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Howdy Jay, On my D14 the only way currant can get to the coil is from the ignition switch. On currant to coil off no currant to coil. There is no other way currant on my tractor can get to the coil to keep the tractor running. Do others tractors have another wire running to the coil? Thanks Kurzy
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Posted By: Steve in NJ
Date Posted: 09 Jun 2016 at 7:54am
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As the guys mentioned a diode will do the trick. 1 amp/50V diode from Radio Shack or a similar store will take care of the run-on problem. We offer a quick disconnect diode module that plugs into an "SI" series Alternator if that's what you're using for the charging chores... Steve@B&B ------------- 39'RC, 43'WC, 48'B, 49'G, 50'WF, 65 Big 10, 67'B-110, 75'716H, 2-620's, & a Motorhead wife |
Posted By: Gerald J.
Date Posted: 09 Jun 2016 at 11:54am
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Kurzy, its common when converting to an alternator to pick up switched power from the ignition wire to start the alternator excitation. That makes even a one wire alternator work better by charging at engine idle without having to spin the alternator fast to get it started charging. That connection needs a resistor, diode, or lamp to limit the current fed back to the ignition circuit that would like the OP keep the engine running with the key shut off. Gerald J. |
Posted By: Kurzy
Date Posted: 09 Jun 2016 at 4:18pm
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Howdy Gerald, This D14 was switched over before I bought it. Must be wired a little different. The only reason I put a diode in because currant was back feeding into alt and killing the battery. I found out one day shorty after shutting tractor down, alt was hot to touch. Never had trouble with after run
as key worked great to cut
power to coil. Test light, no light with key off, light with key on. Thanks for the info. Kurzy
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Posted By: dirtfarmer
Date Posted: 11 Jun 2016 at 7:48pm
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Diode did the trick. Thanks |