Roberts Gorden 75 Manuel D’Utilisation

36 of 47

If problems persist, contact

Roberts-Gordon LLC at

www.rg-inc.com

Heater Operating

No

Trace fault in supervision 

system. See 

Troubleshooting

for Flame Supervision 

System section.

Yes

Is ignition control showing

a "2 flashes" LED code?

No

Is the flame current at

least 1 μAmp DC when

the flame ignites?

Ignition control faulty;

 replace.

See Ignition Control section.

Is ignition lead okay and 

connected?

Is spark electrode okay?

Yes

Replace valve.

Is the gas valve operating?

To test valve, See 

Troubleshooting for Gas 

Valves section.

No

Does the flame light?

No

Yes

Wait 30 - 40 seconds. 

Does ignition spark 

operate?

No

Yes

Flue blower faulty; 

replace

Burner control faulty or wiring 

connections faulty. Repair 

or replace as required

Check for too much vent/air inlet duct. Check for blockage in 
vent and combustion air circuit. Check for faulty air pressure
switch. Check pressure switch hoses for leaks or cracks. 
Do not attempt to circumvent pressure switch circuit to 
place unit in operation.See Pressure Switch section for details.

Does air pressure switch 

change over?

No

Yes

Is 120 V supply at fan 

connections? 

Does flue blower run?

No

Yes

Yes

No

Yes

Fan and limit switch are 

operating normally.

Replace temperature limit 

switch.

UHD 75: Press in reset 

button on manual reset limit 

switch. UHD 100 - 125: Wait 

10 - 15 minutes for limit 

switch to cool. Does fan 

stop running?

No

Is ignition control showing a 

"4 flashes" LED code?

Yes

No

Yes

Turn on controls.

Are external controls

(i.e. Thermostat) on?

No

Yes

Turn on supplies.

Are gas & electrical

supplies on?

Yes

No

 

For optimum heater performance, use only replacement parts sold and supplied by Roberts-Gordon LLC. 
Conduct start-up procedure as shown 

on Page 26, Section 11.