Ok, so why does it not work as insulator, the laws of physics have not been suspended. It turns out that not only isn't "vacuum hose" a suitable insulator for the application, it is rubber hose in general. But you will say rubber is an effective insulator, everyone knows that and yes it is, the issue is with hose and how it is manufactured and its compound.

Is if you take a piece of most rubber hose and a VOM meter and you check resistance from the inside of the hose to the outside you will find there is in fact and in-effect completely resistance,  i.e. isolation. Rubber is a fully effective insulator in that capacity.

Now try an experiment that I can pretty much guarantee virtually no one has tried and place one probe of your VOM at one end of the hose and the other at the opposite end, making sure you are inside to inside, or outside to outside and what you will find is a circuit exists from end to end.

Now if you wonder about this, and do some research it has mostly to do with the carbon that is used in rubber formulation, carbon is conductive and it is what makes rubber hose black.

If you read up, it turns out that GM discovered this back in the day when they had problems with some aluminum parts in their cooling systems getting eaten by stray current. Interesting read if you look it up. It turns out you can get rubber hose without carbon in formulation, but it is not readily available and is pretty expensive.

I discovered this phenomenon on my boat actually which has an aluminum saildrive which requires total electrical isolation from the engine itself. It turns out Volvo provides the OEM hose from the engine water pick-up in the sail drive to the engine water pump (yes I realize it is a stupid design to pull the cooling water thru the sail drive, but it cools the drive also), the OEM hose is special rubber formulation. Over time salt from the raw sea water it draws gets deposited on the interior walls of the hose and this creates a more conductive pathway. But that's another story.

Take away is rubber hose is basically conductive along it's length and current will pass along it, but not through it.

It is better to get a real one. You can buy them online in all the values ​​you want.



The advantage over a rubber hose is that there is a barcode on it from which you can deduce the resistance. I have yet to see the first rubber hose with such a code.

I hope you are not civil servants because this might look bad on your weekly report.