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12v Accessory Sockets Won't Power My Vehicle Air Compressor.
Both 12v sockets are hot and are able to power a 12v to usb adapter for my phone. Neither socket will power my old compressor. The compressor works. I plugged it into the 12v on my Ford and used that vehicle to top off the tires on the C450.
Any ideas? The compressor is at least 12yo and may be as old as 15 years. Will the plug config make a difference? The owners manual for the C450 claims that the 12v plugs will handle a load up to 15A and the compressor has a max draw of 12A so I should not be drawing too much current.
The phone requires much less power, thus low amp (usually 1A to 2A), to charge while the compressor requires the 12A (10x more than your phone). Your socket power is going somewhere else due to wiring issues (ground or hot wire draining power). I'd drop at the dealer for a quick check.
Your old compressor has probably very low internal resistance due to age based issues (especially when it's not turning). Consider this, at 12V and 12 Amps, your internal resistance will be 1 Ohm. If the resistance drops to even .8 Ohms your amperage draw will jump to 15A and it could be that the short peak in high amp load during startup is triggering a safety cutout inside the car to prevent overload. On an older car that has only fuse based protection the overload may be short enough not to blow your fuse and therefore the motor can start turning and resistance will pick up and settle.
If you want to keep that old compressor, I suggest you wire in a pair of alligator style battery clips and just hook it straight to the main battery terminals if you need to pump up your tires.
I suggest getting a viaair one off amazon for around 60-70. I forgot the model I got but it works flawlessly. Small footprint, extremely fast, and not too loud. Gets warm though.
^ Yes Viair are definitely a good option. Just be careful about compressor selection. Most are designed to be connected straight to the battery and not a cigarette lighter socket due to the higher current draws.
Here's a chart of I made ages ago so pricing is a tad out of date perhaps but it'll give you an idea of what is out there. Most of these are designed for full vehicle air systems but the Viair line is available as portable compressors as well.
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