WD-45 & pertronix ignition misfire
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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=146053
Printed Date: 19 Jul 2025 at 4:47pm
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Topic: WD-45 & pertronix ignition misfire
Posted By: ALLISMAN32
Subject: WD-45 & pertronix ignition misfire
Date Posted: 01 Jan 2018 at 3:31pm
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Working on a WD-45 that has a pertronix electronic ignition installed by a previous shop as well as a delco alternator. This thing runs smooth as silk with the alternator disconnected. The voltage with the alt. disconnected is 12.3 at the batt. , 11.8 on the key side of the resistor and 3.8 on the coil side of the resistor. If the alt. is hooked up and the tractor is revved up to make it charge say 15 amps on the ammeter the ignition starts cutting out and the misfiring/backfiring begins. The voltage is 14.3 on the key side of the resistor and 9.7 on the coil side of the resistor. The module receives its power from the key side of the resistor. The exciter wire for the alt. also feeds from the key side of the resistor. Is this the way this system should be? I've never installed one of these pertronix systems before, but have taken them off several 3020,4020 Deeres due to running problems. Thanks in advance for any advice!!
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Replies:
Posted By: DougS
Date Posted: 01 Jan 2018 at 5:48pm
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First things first. How long does the alternator charge at 15 AMPS? It should only charge at that rate for a few minutes and then begin to back off. Your alternator charge wire should go directly to the ammeter and then the battery or battery wire side of the starter or starter solenoid. This way the battery tends to act as a filter. The ignition wire should run off the battery and then through the ignition switch. Run any wire for the Pertronix from the ignition switch. I’d get rid of the resistor and install a 12 volt coil.
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Posted By: ALLISMAN32
Date Posted: 01 Jan 2018 at 8:37pm
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Charge wire for alt., power for key switch , power for light all hook to the negative side of amp guage. Hot wire from starter post goes to positive side of ammeter, therefore all loads are traveling through ammeter which I believe is how it should work. Module is a model name Ignitor, Coil is a Thunder Volt3. The module plate has a Dennys Carb Shop sticker on it and I am assuming everything came from them. None of the components appear to be very old. I am probably gonna put it back to points and I'm sure it will run fine then. I was trying to make whats on there work as several on here praise the electronic conversion. My past experience with the kits has never made me want one on anything I owned. I assume pertronix maybe has some guides on their website?
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Posted By: DougS
Date Posted: 01 Jan 2018 at 9:08pm
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A ThunderVolt3? That sounds like a 12 volt coil. Where is the resistor?
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Posted By: HD6GTOM
Date Posted: 01 Jan 2018 at 9:08pm
Posted By: ALLISMAN32
Date Posted: 01 Jan 2018 at 9:49pm
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Resistor is by oil filter between keyed power and positive terminal on coil. If you disconnect the charge power wire from lug on alt. this tractor runs smooth at any engine speed, hook it back up and instantly backfires and cuts out. I did not check the ohms across the coil to see if it is in spec, website says minimum of 3 ohms for four cylinder. Darndest thing I've ever seen, as soon as the alt. starts to charge the ignition problems begin. I even jumped around the ammeter thinking maybe somehow it was breaking down internally and no change.
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Posted By: DougS
Date Posted: 02 Jan 2018 at 3:21am
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I don't know if the resistor belongs there or not. I'd be more comfortable with a good 3 ohm 12 volt coil and no resistor. I'm inclined to think your alternator is bad. If you have a bad diode, the ripple on the DC voltage could be confusing the Pertronix. Removing the wire from the alternator while the alternator is running in a no-no. Doing so has been known to blow alternators out. The first thing I'd do is find as loaner alternator and try it out. Don't mess with this alternator by connecting/disconnecting it. I's still get rid of the coil/resistor configuration and use a good 12 volt coil. It makes the installation simpler. Removing the Pertronix and reinstalling points may cure the miss problem, but if the alternator is bad you're still going to have gremlins popping up.
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