[TR] TR6 temp gage issues

[dave n]

here is what I did today.  tried to document every detail.  looks to me like 
the sending unit is bad.  both???
btw - fuel gage seems to read fine

did I miss anything?

1 - replace the thermostat
2. started car with lots of choke; idling about 1500 rpm
3. gage starts out pinned left; after a couple minutes it starts to move 
right
4. infrared says temp of t stat housing is 112 and climbing
5. at 120 gage is vertical
6. turn off choke, rev engine; settles in at idle of 1200 or so, which is 
normal (engine is not stock!)
7. tstat housing temperature in the 125 to 130 range; gage is moving right
8. after 5 to 10 minutes, gage has settled just left of the red square under 
the letter H
9. temperature is now in the 150 to 160 range; gage has moved farther right. 
as the temperature passes 170 it [pins right
10. shut off car
11. set up secondary system - positive terminal to voltage regulator, vr is 
grounded as it should be, then vr to gage to sending unit
12.  it still pins right.  this is using separate gage, separate sending 
unit, and completely independent of the cars wiring system except the 
battery and chassis
13.  connected mulitmeter from positive terminal to t stat housing and to 
temperature switch threads.  both read over 12 volts
14.  old switch - which was in the car originally - I used the continuity 
tester - i get 0 when the two probes touch, 1 when one nothing is connected
15.  connecting through the old switch (cold) i get .588
16. swapped original sending unit back in; car was still pretty warm (off 
except for power)
17. temp gage moved to almost full hot
18. disconnected car wiring from sending unit; plugged in "external" temp 
gage system; also read way right
19. temp sensor which was in there - measures 5.6 or so on the continuity 
tester cold
20.  put it in boiling water - continuity tester reads .13