VDO CHT question, increasing wire length Options

[type11969]

Yeah, I know, its crappy and not temp compensated but its what I got so . . .

VDO CHT comes with a short thermocouple which is then plugged into a long wire harness, would lengthening this harness by 6 or so inches make a difference in the reading at the gauge? Seems to me that it shouldn't, the error incurred at the thermocouple to copper wire junction should be the same regardless of the wire length, assuming the resistance of an extra 6 or so inches of wire is negligible. Is this wrong? Is the VDO gauge calibrated to the harness length?

Reason I ask is I recently installed an oil cooler in my bus, at the same time I increased the VDO CHT harness length to tidy up the wiring under my dash. Driving the bus the week I noticed the CHTs to be about 30 or so degrees cooler than usual. Can't imagine the oil cooler really having that effect on the heads. Could also be because it has been hotter recently so it is messing with the lack of temp compensation.

I know, I just need to pull the extra length out of the harness and see what the temp reads then but I'm curious to hear your opinions (and bored at work).

Thanks,

Chris

[purple]

ya know, I studied electrical engineering for 4 years and I think the answer to your question is sure. I think the gauge measures potential between the two sides (since voltage is a measure of potential) if the potential is decreased equally between both sides it should remain the same reading. I think that the shitty connector to the thermocouple would have more loss than 6 feet of 22 awg wire would. I seem to remember that voltage drop over a span of wire was negligable up to 200 feet. I could be wrong...i did switch to computer science (IMG:style_emoticons/default/wink.gif)

[Mark Henry]

Pretty sure you're OK as long as it's NOT the brown thermocouple wire that you be cutting.

[TravisNeff]

(IMG:style_emoticons/default/agree.gif) Well, that is what I heard and that is what I did - used an unmodified thermocouple and installed a pair of wires from the thermocouple to the guage.

[Dr Evil]

Yer fine. You can extend the regular wires without incident. Dont cut the thermocouple wires (you know, yer an engineer). You can buy another loom with a plug to extend it from VDO, or splice it yourself (IMG:style_emoticons/default/smile.gif)

[type11969]

Definitely not touching the thermocouple wires wrapped in that brown jacketing, just the copper wire harness that connects to them. I'm pretty sure it shouldn't make a difference too I just can't explain the reduced temps on the gauge . . . don't see the oil cooler doing it and the ambient temps haven't changed enough to mess with the "calibration" of the gauge that significantly. I'll have to investigate during my bus adventure this weekend down to exciting wilmington DE.

Thanks for the help

-Chris