Thermo Pride MODEL OPA - Manual (Page 61)

All installations and services must be performed by qualified service personnel.
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The operational condition of the flame sensor, or “cad cell”, can be checked by
depressing the reset button on the control module, while the burner is operating.
Count the number of flashes of the LED and compare them to the table below.
Number of flashes Cad Cell Resistance (in ohms)
Model R7184P Model R7997D
1 ......................................... Less than 625 Less than 300
2 ......................................... 625 to 1250 300 to 600
3 ......................................... 1250 to 2500 600 to 1200
4 ......................................... 2500 to 5000 1200 to 5000
If it is necessary to troubleshoot the flame sensor independently of the burner
primary, the following procedure may be used.
CAD CELL CHECKOUT PROCEDURE:
1. Stop burner and shutoff electrical power to the appliance.
2. Open burner junction box (on top of the burner blower) and remove the plug-
in portion of the cad cell by pulling it forward from and clear of the
receptacle. Connect an ohmmeter across cad cell pins. With the cell
exposed to direct room light, the measured resistance should be less than
2500 ohms (in fact, it may be less than 200 ohms).
3. Check the resistance across the cad cell pins with the cell covered
(protected from exposure to ambient light). The resistance should be greater
than 20,000 ohms.
4. If cell resistances are different from above, replace the plug-in portion of cell,
(Honeywell Part No. 130367).
5. Carefully reinsert the plug-in portion of the cad cell into the receptacle. If the
cad cell appears to be functioning correctly, troubleshoot the fan control
module and the safety and ignition control (primary control) module,
according to the Honeywell instructions covering the devices.
B. Cooling System:
NOTICE: Before troubleshooting, familiarize yourself with the Initial Startup
and the Cooling System Troubleshooting Flowchart.
If the air conditioning system will not operate, check the following points before
calling a qualified heating contractor.