OK, if the VDO's TC has Red & Yellow insulation, it's a Type K.
You can use type K extension wire with little problem, and
negligible effect on the calibration (while another poster
expressed concern over the low potential generated, the current is
so miniscule, given typical input impedances, that loop resistance
is seldom a problem - certainly not for 10 feet or so). *However*
you will need to purchase either a pair of Type K TC plugs, OR a
Type K barrier strip for connecting the extension wire to the
probe leads - do *not* use any other type of connector (or you
'can' twist and solder if you wanna go cheap:-).

I've made, calibrated, and used several *thousands* of TC's over
the past 25 years, so I have a bit of experience here. Let me know
if you need more info (BTW, I have a couple of K female mini-plugs
laying around if you want one, then you'll just have to pick up
the male half).

Keith Hughes

> Date:    Sun, 28 Dec 2003 23:02:09 -0800
> From:    David Marshall <vanagon@VOLKSWAGEN.ORG>
> Subject: Re: What makes a pyrometer's cable so special? PT-II
>
> Wow!  I lot of response to my question.  This is great!
>
> The VDO gauge that I am using uses a thermocouple, so says the installation
> guide.  The resistance of it is under zero ohms.  The length of the cable
> that came with the kit is 12' and the additional cable that I bought is 14'
> Measuring resistance on the red wire, it is 1.2ohm and the yellow wire is
> 3.2ohm.
>
> The thermocouple end of the 12' that came with the VDO gauge is simply some
> inexpensive looking 18-22 ga 'eye' connectors crimped on the end of the
> wires.  Each wire is offset by about 1" so they can not touch each other.
> The VDO gauge end of this cable is just the two wires terminating into the
> 'open air'.  As in you have to crimp on your own female spade connectors to
> this end.  To attach the cable to the thermocouple they supply some small
> (M2ish) screws with nylock nuts to fasten the coupler to the cable.  The
> cable looks a lot like the cable you see used between a household furnace
> and the thermostat - i.e. nothing fancy other than a tough outer skin.
>
> David Marshall
>