Low voltage at power outlet

[boyse7en]

Hi all,
My 2007 Accord Tourer is giving me a headache.
Bought a mini compressor to blow up my paddleboard. Plugged it in to the power outlet in the boot and nothing worked. Thought it would be the fuse - nope, that seems fine. Checked for voltage at the plug (ie where the loom plugs into the back of the power outlet socket) and I'm getting 4v.
Bit stumped now. What could causing such a drop in voltage?

 

[F6HAD]

Bad earth possibly? Are you testing your ground from the outlet or chassis? And is the engine running when testing?

 

[boyse7en]

Both...
I tested using a multimeter with the engine on and engine off, using both the earth on the outlet and earned to the body (used the bootlid catch plate). I also tested the courtesy lamp alongside the outlet to make sure the earth was good, and that is showing 11.9v.

 

[Kaput!]

Those mini compressors are a huge power drain so if youve attempted to use it from car battery it would be unlikely to work and would give a low voltage reading from socket.
Even with engine running i have had these things noticeably drop revs given the ampage they suck

 

[boyse7en]

Those mini compressors are a huge power drain so if youve attempted to use it from car battery it would be unlikely to work and would give a low voltage reading from socket.
Even with engine running i have had these things noticeably drop revs given the ampage they suck

It worked fine from the power socket in the front of the car (kept the engine running while pumping), it was a bit awkward to do though so I'd like to get the one in the boot working properly.

 

[Kaput!]

It worked fine from the power socket in the front of the car (kept the engine running while pumping), it was a bit awkward to do though so I'd like to get the one in the boot working properly.

Yes i always use the socket in the tourers boot for tyre pump/travel kettle etc...access ideal.My front socket cluttered with nav/dab/phone cables and a little fiddly to get too.
Maybe wiring or back of your rear socket is damaged somewhere allowing a power drain or perhaps dampness somewhere within affecting voltage? Im no expert but it could be next thing to check