What do I need to replace the parts where the thermometer goes through the windshield, on my 1978 Sundowner?
The parts book shows the following two pieces, where the thermometer mounts in the windshield:
169-420035-9 Boss, OAT, inside half
169-420035-11 Boss, OAT, outside half
The above parts appear to have been used on all the airframes that came factory-equipped with a windshield-mounted OAT thermometer.
Both of these parts show as being available from RAPID, at about $53 each plus tax, S&H (August 2004). It looks like they mount in the acrylic, then the thermometer slides down into them. I have never installed one, so I can’t vouch for what’s involved.
On the thermometer itself, there are two seals on the shaft where it passes through the mount/housing:
28-41 Seal, Temp Gauge
These are seals between the thermometer and the mount/housing, as opposed to between the housing and the windshield. They are available from RAPID for $3.67 each, and are shown as being in stock in the Dallas warehouse (August 2004).
Personally, I favor replacing the windshield-mounted thermometer with an STC’d Davtron digital OAT (or similar unit), whenever a windshield is being repaired or replaced. Ditto for any windshield-mounted compass. Never have been a big fan of deliberate holes in a windshield, aside from the perimeter mounting holes.