T
HERMO
90 / 90 S
6FUNCTIONAL TESTS
6-1
6. Functional Tests
6.1 General
This section describes the on-vehicle and off-vehicle
testing of the heater to check for proper operation.
WARNING
The heater must not be operated, not even with timer, in
enclosed areas like garages or workshops not equipped
with an exhaust venting facility.
6.2 Adjustments
6.2.1 Adjustment of the CO2 Content
A change of the combustion air volume set by the
manufacturer may be performed by rotating the air set
screw.
Setting Procedure
Clockwise rotation: CO2 value decreases (prior to
measurement; heater must have been in operation for at
least 5 min).
Coarse setting: Rotate air set screw clockwise fully in
and then back one turn.
6.3 Components Testing
6.3.1 Temperature Sensor Resistance Check
During electrical testing of the temperature sensor using
a digital multi-meter, the following readings should be
obtained:
Resistance at 25 °C (77 °F): 990 … 1010 Ω
Test current: < 1 mA
6.3.2 Glow Pin Resistance Test
During electrical testing of the glow pin using a digital
multi-meter, the following readings should be obtained:
Glow pin: 12 Volt (red) 24 Volt (green)
Resistance at 25 °C: 0.324 … 0.360 1.3 … 1.44 Ω
(77 °F):
Test current: < 5 mA < 5 mA
6.3.3 Flame Sensor Resistance Test
During electrical testing of the flame sensor using a
digital multi-meter, the following readings should be
obtained:
Cold Test:
Resistance at 25 °C (77 °F): 2.6 … 3.4 Ω
Test current: < 5 mA
Hot test:
Resistance at 800 - 1000 °C: 12 … 15 Ω
(1472 - 1832 °F):
(ceramic rod red hot over a length of approx. 20 mm)
Test current: < 5 mA
6.3.4 Combustion Air Fan Test
The motor speed check must be performed with the
heater assembled and within the operating voltage
range. During the test, check for grinding noises.
NOTE:
For the motor speed check, the fan cover must be
removed. Prior to re-installation the gasket is to be
replaced.
CAUTION
Pay attention not to break off the locking cams, otherwise
replace cover and gasket.
Speed in control range min. 1800 rpm (±9%)
Speed in control range max. 6100 rpm (±9%)
In the event speed values are out of tolerance replace
combustion air fan (see 9.2.5).
NOTE:
On the Thermo 90 the function of the combustion air fan
can be checked with the diagnostic computer or the
components tester.
On the Thermo 90 S, the check is performed by means
of the PC heater diagnosis.
