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Robertshaw gas-valve troubleshooting starts with the exact appliance and control model—not a generic checklist. A standing pilot with a thermocouple or thermopile follows a different diagnostic path from an electronic intermittent-pilot system. Homeowners should limit checks to those allowed by their appliance’s instructions; gas-control testing and repair belong to qualified service personnel.
Identify the appliance and control before troubleshooting
Record the appliance type, fuel, gas-valve model or part number, ignition-control model, and the precise symptom. Find the appliance rating plate and read the label on the control itself. Then locate instructions for that exact appliance and control in Robertshaw’s document library.
Do not assume controls are interchangeable because they share the Robertshaw name. The 7000 family is used with standing-pilot, intermittent-pilot, direct-spark, and hot-surface ignition arrangements; 7200 controls are used in direct- or intermittent-pilot applications. Terminals, fuel/application compatibility, and diagnostic procedures vary. Robertshaw’s gas-valve product overview describes these families, but the appliance specifications and exact control manual govern a particular installation.
| What you observe | System or guide to identify | What the symptom can indicate |
|---|---|---|
| Pilot lights but will not stay lit | Standing-pilot control; Robertshaw 700 Series instructions apply only to covered models | Pilot operation, thermocouple/thermopile output, connections, or the automatic-pilot magnet |
| No spark and no pilot gas | Intermittent-pilot control; use the matching control guide, such as the 780U/DS20 guide when applicable | Power, transformer, thermostat/limit circuit, wiring, or ignition control |
| Spark but no pilot gas | Intermittent-pilot control | Gas supply/manual valve position, control voltage, wiring, or valve fault |
| Pilot flame but no main burner | Intermittent-pilot control | Flame proving, sensor or ground, wiring, ignition module, or valve coil |
| Main burner starts and stops repeatedly | Intermittent-pilot control | Use the exact model’s short-cycling troubleshooting path; several system and control causes are possible |
The 780U/DS20 guide separates these symptoms rather than treating them as one “bad valve” problem. Use it only for controls covered by that guide.
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Why does a standing-pilot flame keep going out?
For a control covered by Robertshaw’s 700 Series Gas Heating Controls manual, revision 1-120N dated 04/24, the listed possibilities include improper pilot operation, low thermocouple or thermopile output, and an inoperative automatic-pilot magnet. The manual’s diagnostic sequence is for trained service personnel; it is not a homeowner procedure.
What the technician checks
- Pilot operation: Check whether the pilot is operating as specified for the appliance and control. Do not adjust or dismantle the pilot based on instructions for a different model.
- Thermocouple output: The 700 Series manual specifies a closed-circuit test. For the covered controls, output below 8 millivolts calls for replacement with a Robertshaw 1970 or 1980 thermocouple. This threshold and replacement guidance are specific to the manual’s covered setup, not a universal Robertshaw specification.
- Connections and millivolt circuit: The manual specifies a 0–1000 mV meter range and distinct closed-circuit terminal arrangements for its valve-operator, thermostat, and thermopile/magnet checks. Its listed values are greater than 100 mV for the valve-operator system, less than 80 mV for the wall-thermostat check, and greater than 325 mV for the thermopile/magnet check. A technician should follow the manual’s exact terminals and procedure; the numbers are not interchangeable readings.
- Low or abnormal readings: Robertshaw directs the technician to clean and tighten connections and check pilot output when the thermopile/magnet reading is below 325 mV. A high thermostat-path reading can point to leads or connections, excessive wire length, wire gauge, or thermostat contacts.
- Automatic-pilot magnet: If the covered thermocouple test exceeds 8 mV but the pilot still will not remain lit, the manual describes a magnet check. If the magnet does not operate properly, it directs valve replacement rather than an improvised repair.
These checks involve the gas-control circuit and should be performed only by a qualified technician using the exact instructions for the installed control.
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- Normally closed solenoid
- Compact size with high flow rates
- Standard nema terminals
- Inlet filtered screen
- Various gas types: natural, manufactured, mixed, lp and lp/air mixtures
Intermittent pilot: pinpoint the step that fails
An intermittent-pilot system uses an ignition control and electronic flame sensing; it is not diagnosed like a standing pilot. Robertshaw’s 780U/DS20 troubleshooting guide (2024) organizes diagnosis by the failed stage. Its 24-volt checks are procedure specifications for that guide, not a general test for every gas valve.
“No spark, no pilot gas”
The guide’s diagnostic path considers upstream power and call-for-heat components—including transformer, thermostat, and limit circuit—as well as wiring and ignition control. A missing spark does not by itself establish that the gas valve has failed.
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“Have spark, no pilot gas flow”
The guide distinguishes gas supply and manual-valve position from control voltage, wiring, and valve faults. A qualified technician must determine which branch applies; do not open the valve or attempt to force gas flow.
“Have pilot flame, main burner will not turn on”
This symptom can involve flame sensing/proving, the sensor or its ground, wiring, ignition module, or valve coil. The pilot’s presence alone does not prove that the ignition control has accepted the flame signal.
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“Short cycling of main burner”
Repeated burner shutdown is a separate symptom in the guide. Follow the exact control’s troubleshooting sequence rather than replacing the valve based on cycling alone; the guide includes potential control, wiring, and system causes.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What a homeowner can safely check
Robertshaw’s Intermittent Pilot Ignition System Homeowner Operation Manual, revision 1-864 Rev C, 11/24 is specific to the system it covers. It says not to use a match or manually light the appliance. The limited checks it permits are:
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- Confirm the thermostat is calling for heat.
- Check that electrical power is present.
- Check that the manual gas valve or gas cock is on.
For the SP845 lockout model addressed by that guide, follow its documented reset instruction. If the system still does not start, Robertshaw says: “If the system does not start, call the installer of the system or a qualified servicing agency.” For any other appliance or control, follow its own homeowner instructions.
Quick Recap
When to stop and call for service
- Do not open, rebuild, force, or adjust a gas valve unless the exact manufacturer instructions call for a task that a qualified professional is authorized to perform.
- Robertshaw’s 700 Series manual says a control exposed to water must be replaced. Do not try to dry out or reuse a water-exposed gas control.
- Robertshaw’s 7200 product description states: “To prevent unsafe attempts at repair, screws requiring special drivers are used and replacement parts are not available.” Follow the manufacturer’s replacement guidance; do not seek an improvised internal repair.
- If a gas valve will not shut off, stop generic troubleshooting and follow the appliance/control manufacturer’s emergency instructions. Contact qualified service personnel; do not continue operating the appliance.
- Leave voltage, continuity, flame-sensing, pressure, and gas-control testing to qualified personnel using the exact model’s documentation.
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