<VV> Cylinder head temp thermister

[Craig Nicol]

Dave asked:
<snip>Before my engine was rebuilt, the cylinder head temp gauge worked
(even
though the engine barely did). Now that the engine is rebuilt, the gauge no
longer works. I have tested good continuity from the disconnected gauge wire
under the dash back to the end disconnected from the thermister. However, I
get a full open from the thermister tip threads to ground (the head) while
cold. I haven?t pulled the thermister yet due to it?s location behind the
exhaust tube. What resistance should I expect between the thermister tip
threads and head when cold? Is there any reason why I shouldn?t run the
engine with the lower shroud off to warm up the head for another test? Can I
use my resister substitute box from the thermister wire to ground to test
the gauge? What resistance should I try? I don?t want to blow up my gauge.
Also, with the key off, I get about ? gauge reading, key on, zero. I don?t
remember what I got before the engine rebuild. I can?t find any testing
information in the green book.

Thanks in advance
Dave Thompson 63 Spyder <unsnip>

It sounds like your thermister hase gone TU. At room temperature, the
thermister should have about 5000 ohms between the top and the threaded
base. Likely, someone allowed the stud to rotate as the nut (usually rusted
on) was removed and the element is no longer in contact with the tip.

Be super cautious when removing the thermister. See if you can get PB
blaster or Kroil into the threads then work it back and forth as you unscrew
it. It's really easy to break-off the lower portion of the threads in the
head; much easier to wiggle it out when it's still intact.  Sorry to be the
bearer of bad news - let's hope it shows good for your retest!
Craig Nicol

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11:31 AM