unreliable temp gauge test

[murray720]

i just got my temperature gauge working on a 63' 220s.

in my pile of parts i found what i thought was a good replacement but i wanted to test it before i took apart the instrument cluster. while holding the gauge portion i placed the capillary part in the head ...nothing. so rather than what i thought would be wasting my time, i scrapped the replacement and was in search of another. I found a second replacement and went through the same test ...still nothing. Primarily to change bulbs, i decided to take apart the instrument cluster and install it anyway ...THE GAUGE WORKED. my best guess is my test wasn't working because the gauge portion needs an enclosed space to prevent heat dissipation.

um, who knows

[300SDog]

Yep, I've seen 111 temp guages fail - happened to me when wire from sensor at cyl head got roasted from lack of insulation.

Did you hold the guage in your hand while it was wired to cylinder head sensor for testing? My guess is these guages are partially electric even on 111's, except maybe the oil pressure guage - so they need to be well grounded.

Later model 108, 114, 116's have circuit board type back on instrument clusters makin me think each guage has more complicated wiring than we realize.

[murray720]

yes, i was holding it in my hand while testing and as i recall with the first one i even tried testing it by placing the capillary in boiling water. it's strange how what looks to be a purely mechanical device would still need a ground.