<VV> Stewart Warner Head Gauge Question
FrankCB
frankcb at aol.com
Wed Aug 19 11:13:28 EDT 2009
Seth and Bob,
Good points, Seth. Except we should distinguish between the THERMOCOUPLE type of temp gauge that you describe and the THERMISTOR type that is used in stock Corvair Corsas. As you correctly describe, the non-stock thermocouple type functions by generating a small electrical charge from the junction of the two wires located in the hot area. In contrast, the thermistor sensor is a variable resistor whose resistance changes with temperature. An external 12 volt source sends electric current through this variable resistor and the measures the resulting current on the gauge in the dash. A higher temp produces a lower resistance resulting in a larger current flow giving a higher reading on the gauge. The stock setup uses only a single wire from the thermistor.
Incidentally, many years ago Stewart Warner also had a gauge-with-thermistor kit designed specifically for the Corvair. I installed this single unit in a number of my Corvairs and it was the first item I removed when I had to finally let the Corvairs go to that great big boneyard in the sky.
Frank "long memory" Burkhard
In a message dated 08/19/09 02:48:31 Eastern Daylight Time, Sethracer writes:
In a message dated 8/18/2009 8:10:31 P.M. Pacific Daylight Time,
bgilbert at redshift.bc.ca writes:
I assume they represent a connection to ground through the ring which I'm
guessing is a variable resistor that reacts to the heat. Is that correct?
Simple question - does the second wire need to be replaced?
Regards,
Bob
No, Bob. Because what you have there is a thermocouple. The two dissimilar
wires are crimped to the tab on that ring. Where the two wires meet, the
junction of the two materials create a small current, that is proportional
to the heat applied to the junction. The gage reads that small current and
displays it as the temperature of the junction. All you need to do is strip
both wires and crimp them onto another ring terminal. The gage should
function as it did before. Unless you really want to fool around with a ring
under a spark plug, you should crimp on a 3/8" ring terminal and, using a
short, socket-head screw, mount the ring terminal into the hole on the other
head that is normally occupied by the temp switch (on the 110/95). If you have
a 140, the hole may already be occupied by a switch or thermocouple for
the Corsa dash. Unless the original thermocouple is already broken (pretty
common) you should not try to remove it. I have about a 20% success rate.
Usually the outer shell breaks off, resulting in a lot of work. If it is
already broken? What the heck! The 110/95 heads have a coarse thread in this
hole, the 140 and 180 heads use a fine thread.
Seth Emerson
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