I am taking my VDO temperature gauge reading off the same sensor that leads to the instrument cluster L to H sweep gauge. Would running these two off the same sensor make any difference to the GP sensor on the other side of the water flange?
I thought the glow plug sensor was an on or off thing. If warmer than x degrees then no relay kick in. Is that not true?
The thread on the sending unit for my aftermarket gauge (it's a VDO also) is 1/8 NPT, which looks very similar to M10 x 1, so you might want to double check on that.