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Filtering electic noise on a tractor.

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plankwood

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I think I have this on the right place but if not please remove it if I am not right.

I have a old 8N Ford tractor I set up with a 12 volt conversion years ago and now I added a electronic spark module from Pertronics.
I seem to have some problem with the electronic points converter making the alternators burn out. I have replaced two now. I had the old points ignition for a few years and never had any alternator problems until now. My digital multimeter readings jumps all over when the tractor is running but not when the lights are on.

Any help would be great! I am fair with electrical stuff and can handle basic electronical things as well.
 
Have you tried resistive plugs and plug wires? If not, that is where I'd start. If that doesn't work, take off the radiator cap and drive a JD diesel under it. :D
 
Alternators need a battery to stabilise the output.

You said that the voltage is all over the place. All the alternator circuits that I've seen, including this **broken link removed** have the alternator connected to the battery. Now if the voltage is changing on the alternator, either the battery voltage is changing or there is some voltage drop between the two.

The only thing in between should the ammeter. What is the ammeter showing while the voltage is varying?

You could try bypassing the ammeter and seeing if the voltage stabilises.

It could also be that there is just too little electrical load on the system. However, there were alternators on cars from about 1970, and cars of that age had just about no electrical load when driving unless something was turned on.

I converted a car (well a Reliant Supervan III, so nearly a car) from a dynamo to alternator, and I fitted capacitor discharge ignition, and had no problems. However, it was 12 V to start with and it didn't have an ammeter. The only electrical load that was always on was the gauges, but I probably left the heater fan on most of the time.

The electronic ignition is likely to reduce the current taken by the coil, especially at low engine speeds. I would have thought that the battery would absorb the minimum current that the alternator produces, but you could be overcharging the battery.
 
Thinking about it I have a similar symptom on a 1972 chevy truck I purchased to move 5 years ago. The voltage reads high on a analog meter but was OK with the lights on.

The truck did not charge when I first got it. A mechanic replaced the external regulator and maybe the alternator. I have no idea how close to the factory setup this is. I expect it was 12V to start with.

Battery was good.

I just left the lights on during the moving trips. Have not used it since.
 
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Might try a transient voltage suppressor, it might just be some kick voltage from the amp meter because of the quick switching of the new ignition. Put it right at the alternator output.
 
Is yours the side distributor or front distributor type?
Is it still using the original wiring system?
What kind of alternator?


I have a 9N I restored about 5 years ago that I put electronic ignition on. It fried the alternator regulator after about 10 minutes run time as well.
I added two ignition condensers to the 12 volt supply on the ignition side. One is the old one that was for the points system and is in the distributor connected to the 12 volt supply for the electronic ignition module and the other one is on the 12 volt supply lead for the external coil I used when I converted it to a external coil system instead of the original "brick" coil that ford had on the distributor.
The aftermarket 12 volt brick coils for the old front distributors are junk anyway being the ones I had always burned out after about a year.

The last time I replaced the Delco 10si alternator on my old Ford I added a condenser on the exciter lead just for added protection. So far its been a few years and everything is still working well so I can only assume the condensers are filtering out what ever noise the electronic module makes.

Its the best I can guess at without more information.
 
Could the problem be that the alternator voltage regulator loop becomes unstable, and is oscillating at an audio rate?

This would take a scope to see, but I have seen this in aircraft, especially those that locate the battery in the aft part of the aircraft for weight/balance. The resistance of the long wires between the battery, alternator, and the voltage regulator is the root cause of the feedback system going unstable.
 
I am not sure myself but I have fried the regulators on two tractors from apparent ignition noise issues in the last year. The old tractors tend to have noisy electrical systems and the newer Delco alternators just don't seem have the same quality of regulators they used to have.
The old ones apparently could take a considerable electrical beating without problems but the new ones tend to give up rather easily.

I think the OP may have the same problem as I did. The crappy quality of new parts not working with the old systems. :(

Since then I have been adding ignition condensers to each tractors electrical system with one near the ignition coil and another near the main amp meter connection to work as noise snubbers and so far it seems to work great. The old 9N is the first to get a third one on the alternator exciter lead.

It sort of worries me now with the drop in quality of the Delco alternators due to my having put dozens of them on other peoples old farm machinery over the years. I may be needing to put snubber caps on for them if they ever wear the old Delco alternators out or go to electronic ignition systems. ;)
 
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Thank you everyone! The condensor filters work great and I have been using the old 8N all winter and have yet to have the new alternator give me any problems.

I even added 3 big 55 watt halogen lights to it so I can work at night now!
 
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