User's Manual

7 Maintaining the product
21
2. Remove discharged batteries/rechargeable batteries and insert
new batteries/rechargeable batteries (4x 1.5 V, type AA,
Mignon, LR6) in the battery compartment. Observe the polarity!
3. Set on and close cover of the battery compartment (clip must
engage).
4. Switch the instrument on.
Changing the valve or valve stem shutoff
DO NOT ATTEMPT to change the valve stems. Changing the valve
stem shutoff or valves themselves will void the warranty.
Send the measuring instrument to Testo Customer Service.
Cleaning the vacuum probe
Contaminants such as oil may impair the accuracy of the vacuum
sensor.
CAUTION
Carrying out cleaning with the probe connected may result in
damage to the probe!
> Remove the vacuum probe from the testo 557!
CAUTION
Damage to the sensor due to sharp objects!
> Do not insert any sharp objects into the probe!
1. Remove the vacuum probe from the testo 557.
2. Put a few drops of rubbing alcohol into the sensor opening.
3. Seal the opening by placing your finger on it and shake the
vacuum probe briefly.
4. Remove all the alcohol from the probe.
5. Repeat this process at least twice.
6. Leave the probe to dry for at least 1 hour. To dry the sensor
faster, you can connect the probe directly to a vacuum pump
and draw vacuum.