Option 9168 - Outside thermometer 60mm ºF part 644.741.601.07
Option 9169 - Outside thermometer 60mm °C part 644.741.602.06
Option 9170 - Outside thermometer 80mm ºF / °C part 902.741.601.01
The most common construction of a mechanical remote car thermometer consists of a sensor body filled with ether (diethyl ether, (C2H5)2O), which is connected to a pressure gauge by means of a capillary tube. The boiling point of the ether is very low (34.6 ° C) so that the vapor pressure of the boiling ether is already considerable at around 40 ° C. As long as there is still liquid ether in the system, an equilibrium vapor pressure is established at every temperature. This equilibrium is a physical property of the ether and the temperature is clearly described by the pressure. The pressure can be read on the display of the knife. Most conveniently, this pressure indicator is designed as a temperature scale so that the existing temperature can be read off directly.
The most common mistake is that the ether has evaporated, due to a break in the capillary tube or possibly other leaks. In particular, the tube is often twisted by the sensor in the cylinder cover if it is improperly removed and jumps off. A repair usually consists of replacing or soldering the capillary tube and refilling the system with ether.
Danger! Ether is volatile and extremely dangerous. The colorless vapors are much heavier than air and can "flow" for long distances, so it is ESSENTIAL to keep open flames, smoking and electrical sparks away.
The following are required for the repair: soldering iron (electric), tin solder, flux, desoldering pump (recommended), capillary tube or pipe section (when patching).
For the filling: ether (commercially available), a suitable mug with hot water, a ditto with ice water.
l. Remove remote thermometer. If the capillary tube is to be replaced, it can be divided if necessary to simplify removal. Make sure that the protective spiral or the protective braid is not damaged. Completely remove the pressure gauge, also from the combination instrument, if this is the case.
2. If the old capillary tube is not to be used again, unsolder the tube both on the feeler and on the scale. When the pipe will be patched together it is not strictly necessary to unsolder it. Sometimes it will but this makes it easier to mount the protective spiral.
The pipe comes with tin soldered. A soldering iron with around 150 W power is sufficient.
Exactly be careful not to let tin get into the small holes. At the best to use a desoldering pump.
3. When replacing the entire pipe: First solder the end to the sensor.
Make sure that no tin clogs the small pipe opening. Therefore the pipe
let it reach into the feeler a little. This also has the
Advantage, when filling the sensor, an air bubble over the ether
guarantee.
->picture one
4. Now the feeler should be filled with ether. Arrange two cups with ice water or hot water (tap warm water is sufficient, the ether boils at about 35 °).
Insert the free end of the capillary tube into the ether and hold it tight. Then immerse the probe in hot water. If after a while no more air bubbles can escape through the ether, immerse the sensor in the ice water. Ether is now sucked into the feeler. After a while, repeat the process until no more air bubbles escape. The feeler is now full.
->picture two
5. When soldering together, it is useful if possible to leave the sensor in the ice water and in any case never let the temperature of the sensor rise above about 30 ° so that the ether does not escape again.
When the entire capillary tube has been replaced, solder the tube end to the knife.
If the pipe is to be patched, slide a sleeve made of pipe with a slightly larger diameter on the pipe and then solder it together, taking care that no tin solder creeps into the capillaries (also keep a distance here). The pipe ends to be mended must be absolutely clean and not clogged. Check carefully that all soldering points are tight.
->picture 3
6. The repair is now complete. If necessary, restore the protective spiral or protective braid. If necessary, the remote thermometer can be calibrated in boiling water at 100 °. The needle on the knife can be carefully removed from its axis and reassembled in order to obtain the correct display. The latter should only be necessary if the thermometer was also mechanically damaged. Capillary rupture alone does not normally affect the calibration of the display.
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