SECTION VIII
8.0
FAULT FINDING
The following section covers only simple faults that may occur. No attempt has been made in
this section to cover highly technical faults.
PROBLEM NO. 1: Unit does not turn on when power “On/Off” switch is depressed.
PROCEDURE &
EXPLANATION:
If unit does not turn on at all, check battery voltage using a voltmeter. If
battery voltage is lower than 6.6 volts, the voltage is too low to illuminate
display. Replace battery. (See Section VII Paragraph 7.5). If battery is
okay, check power “On/Off” switch using an OHM meter with the battery
disconnected. Switch is a double pole, single throw (DPST) unit. Both
sections should normally show open circuits. When depressed, ohmmeter
reading should be less than 2 ohms. If switch is not OK, return to factory
or authorized service center for repair.
PROBLEM NO. 2: Unit stays on all the time, even though “On/Off” push-button is depressed.
PROCEDURE &
EXPLANATION:
This symptom is usually indicative of a faulty power “On/Off” push-
button switch. Check the switch with an Ohmmeter as explained in
Problem No. 1 above.
PROBLEM NO. 3: When turned on in normal air, unit does not read 20.9 ±0.2, and nothing
happens when the simple push button calibration procedure is followed.
PROCEDURE &
EXPLANATION:
If either the power “ON/OFF” switch or the display light switch has a
faulty contact, it will not be possible to perform the calibration. These
switches are both Double Pole Single Throw (DPST) switches, which can
be easily checked with an ohmmeter. Remove the battery when making
ohmmeter checks. Return to factory or authorized service center for repair.
PROBLEM NO. 4: When unit is turned on, in air, unit does not read 20.9
±
0.2. When simple
push button calibration is attempted several times, the readings are
random, and always too low (less than 20.9). LCD does not indicate low
battery voltage condition.
PROCEDURE &
EXPLANATION:
The above symptom indicates that the oxygen sensor within its barrel has
reached end of life and must be replaced. Follow replacement procedures
given under Section 6.0.
17
