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You bring up a very interesting point.
I have read about these getting blamed for circuit failures. But in my realm of thinking on how these work, they shouldn't.
I have looked inside them to find no moving parts like a relay has.
I see that they have only coils of wire. They should not be carrying the actual current of the cicuit. These are parallel to the operating circuit. Like a shunted circuit.
One coil is wound one way and one wound the other way. Each representing half. Each one side of the car.
The current that travels through them cancels each others, magnetic field.
If only one of the coils (half circuit) becomes unbalanced (bulb out) that would be induced a current field into a third coil of wire that is in the center of those two other coils.
That coiled wire tranfers that induced current. It is routed to the warning light bulb through it to ground. Light on!
These wires have a thin insulating coating on them. They actually call this wire, magnet wire.
It is used in relays and transformers. I know of failures that can be caused by vibration of the wire themselves. I don't mean by the shaking of the car but the current flow itself passing through them. Heating and cooling too!
Ever heard a street pole transformer hum outside your house. AC or 60 cycles per second causes the hum. That's what we hear. It also is moving the wires inside it.
I know we have 12 volt DC. But it is generated by a AC dymo i.e. alternator. The DC is not a pure smooth DC. The diodes in them are a brute force cheap device. The auto manufactures use the best cheap stuff they can get!
The battery absorbs a lot. In some cases a capacitor has to be added to keep hum out of the radios power circuit. Called a choke or filter to electronic buffs.
Under certain low speed, bad ground and or high load conditions the alternator does pulse a more coarse wave than normal causing the whole system waver.
I surmise that it may be something like this this that the electrical designer discounted in the specs. for the coating and winding of the magnet wire.
Operating conditions vary per car and the quality of the componets in general through out the spectrum of manufacturing.
In other words: Some do, some don't! Have a problem!
You may not be able to define it as a broken solder joint or unsolder wire.
Its most likely leakage within the coils to the other coils. A device called a megometer that induce a voltage may be used to test insulation. The highest ohm meter sensitivity may show something inside. Then it would be all about rewinding and that would be a tough repair!
Replacing it was the best thing other than check out your electrical charging system and maintenance habits. A common thread between the two bad sensors.
Good Luck, cause it's all just a guess!
Call on Bricksters. Jorrell and Art Beinstein. They may have better thoughts since their our electronics masters.
Phil
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