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I'm working on a cub cadet zero turn with a 25hp kholer twin engine. When i engage deck the mower loses power. I checked the coils, and one was not firing. I bought an after market coil, put it on the engine and hooked up the kill wore that goes from the key swotch to both coils. One coil cuts out.If I take one kill wire off the both fire. The kill wore runs from one coil to the other coil. Same wire. It dosen't matter which kill wire is taken off, both coils work if one kill wire is removed. What is happening?

There is a black wire attached to each of the two coils. Each wire goes through its own diode on its way to the key switch to find a ground in the off position to stop the engine. Understand that a good diode will only allow currant one way. In the on position if one of the diodes was to go bad as in a burn out no contact that cylinder would continue to run in the off position but also if the diode was bad allowing current in both direction the two cylinder can see each other and the wire with the bad diode will seek a ground in the other coils kill wire. I have seen both ways happen. Because you are working on a Kohler it appears they use one diode . GENUINE OEM KOHLER PART # 25 755 31-S; DIODE KIT

Lets start with the actual model and spec of your Kohler engine. And all the kohler engines that have worked on the talkback diode was built into the ignition module itself, not a separate items like Briggs.

As IL probably thinking the same thing as I. Most Kohler twin engine coils have the diode built in the coils themselves. The working coil probably has a bad steering diode. Kohler actually recommends replacing both when you have this problem as failure can lead to other coil related problems.

But as IL said we need the model and spec of the engine to look it up to be sure.

so he should be able to use a ohm meter to connect from the frame of the coil and the kill wire tab then switch to find out if it is one or both ??

Rocky J said:

so he should be able to use a ohm meter to connect from the frame of the coil and the kill wire tab then switch to find out if it is one or both ??

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No he needs to replace both coils, because there are issues with coil compatibilty where if the coil part numbers don't match can cause issues with burning out the old coil. Kohler made updates to the coils were the old coil kill system was low voltage whereas the new coil and could translate to the aftermarket coils use a high voltage kill system and will damage the none high voltage coil.

smallenginerepairs said:

I'm working on a cub cadet zero turn with a 25hp kholer twin engine. When i engage deck the mower loses power. I checked the coils, and one was not firing. I bought an after market coil, put it on the engine and hooked up the kill wore that goes from the key swotch to both coils. One coil cuts out.If I take one kill wire off the both fire. The kill wore runs from one coil to the other coil. Same wire. It dosen't matter which kill wire is taken off, both coils work if one kill wire is removed. What is happening?

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I bought another coil from the same company as the first i replaced, and it runs fine and the kill wire kills both coils as it should. Problem solved, but when replacing one coil in the future, I will change both. I guess it's like changing a headlite on a car, you might as well change both, because the other one will go out soon anyway.

I purchased a used Craftsman G8400 that had an issue with the engine bogging down when the PTO was engaged. The spindles and blades had rags entwined in them and I thought that was the cause of the issue. I went ahead and bought the mower. When I got home, I removed the rags and checked the spindles and pulleys and they moved freely, but the engine still bogged down. I checked the spark and found only the left cylinder firing. I bought a new Kohler coil and installed it. I rechecked the spark and found the left cylinder was still the only one firing, the new coil side was dead. I switched the coils around and now the new coil fired but the old one wasn't firing. I tinkered for about an hour and was at a loss to understand the situation.

When I bought the mower, it had a 32 584 25-S coil on the dead side and a 32 584 09-S coil on the good side. This combination of coils does not work together. I bought a new 32 584 25-S and replaced the "bad" 32 584 25-S with the new coil, and now the new coil was still not firing. I searched the forum and found this post and went out and pulled the 32 584 09-S coil out and had both coils being the same part number and that was indeed the solution.

So thanks to everyone for posting about the incompatibility of the Kohler replacement coils.

I just replaced two coils on Bad Boy mower, one was bad and brand new part. Third time this year I have gotten defective brand new part. When it happens, it really throws a wrench in the works.

Tiger Small Engine said:

I just replaced two coils on Bad Boy mower, one was bad and brand new part. Third time this year I have gotten defective brand new part. When it happens, it really throws a wrench in the works.

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Yes it does.

But I just had a new incompatibility problem. Order through a wheel motor but the new supposedly wheel just won't as a replacement. Darn 24V battery chargers just don't replace Hydro Gear wheel motors.

Now I have wait a month to get my money back because Amazon will not send the correct part. Of course I got the right one coming from my distributor today but it is costing an extra $80. Glad I gave an estimate with the higher priced part.