This is probably a pointless question. Picked up a Motorcraft starter solenoid since mine went missing off an OT car. Upon removing the solenoid on the metal back plate there is a felt where there is normally either a bump or nothing. Is this merely a vent or does it require a drop of oil from time to time, like on old fan motors that would use a reservoir felt pad to keep the end bearing lubed. It's been a while since the car had an original solenoid so I can't remember if it has the same 'vent' or if this is an engineering update. Box has SW-7663 / B6AZ-11450B / 3303619 Solenoid is stamped Motorcraft D2AF-11450-AA Thanks.
Found this old thread through a Google search as I have the same question. I'm finally getting back to the reassembly stage of my Tiger. Over the years, I've bought replacement parts, one being a new starter solenoid. Upon taking this now 25 year old, new Motorcraft solenoid out of the package, I immediately noticed a tiny felt pad attached (see pic). I arrived at the same questions as you, Mike, vent or oiling pad? I'm reluctant to agree with the idea that it's a vent, as these things have been made for many years without one and they're quite reliable. So, when they do fail, it's likely due to worn out contacts or a sticky solenoid shaft that no longer moves, likely due to internal corrosion. So, my thinking is, if it's a vent and is to be left alone, then water surely will be wicked inside. If it's to be oiled, this may extend the life by keeping the solenoid shaft lubricated and less prone to corrosion. Honestly, I'd prefer the old design and the felt to not be there at all. There were no instructions on the packaging. Anyway, I'm going with a drop of oil which will retard moisture intrusion and provide a bit of lubrication, needed or not.
I’d assume the felt blocks what is capable of getting inside. As Steve mentioned, electrical devices don’t require oil. Sure, generators and such had places for a few drops of oil, but that was for bushings.
I'll repeat, it's just a vent. Keep in mind that's not the only place moisture can enter; each of the bolted wire connections can possibly allow moisture to enter, the vent is located at the lowest point to allow it to drain if present. Second, oiling the vent does two bad things. One, it will 'seal' the vent and prevent moisture if present from draining, and two, the electrical contacts are located right above the vent and getting any oil on them will cause burning and shortening of the contact life. If any lubrication is needed, it's done with factory-installed grease that will stay in place and not 'run' into places where it shouldn't be. That's why when you install points, you apply grease to the rubbing block, not oil.
I imagine that the reason there’s a vent is to relieve the air pressure pulse that is generated every time the contact disc cycles from on to off. There’s a lot of thought and engineering in even simple automotive devices.
As Steve mentioned, it's just a vent. Underhood temps change from freezing to oven hot. Condensation happens, components need to be allowed to breath and drain. Found an old non-Ford solenoid in the garage, it was quite rotted(from the inside) on the plate, no vent. Recall a few generic solenoids that were built flipped back in the 90s. Very annoying as you would mount it in the correct orientation and only note when wiring that the 'S' and 'I' terminals were flipped.
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