Girard gswh-2
What it is
Girard GSWH-2 (Lippert) tankless, 42,000 BTU, very common in towables. Needs 12V DC (under about 3 A). Fires on LP only. Also sold under other RV brand names, so check the label.
Key numbers (confirm against the manual)
Inlet gas: about 11 to 14 in W.C. running. Manifold: about 1.5 to 7.8 in W.C. Starts at about 0.70 GPM and keeps running down to about 0.60 GPM.
Temperature: adjustable about 95 to 124 F, factory default 115 F. ECO (high limit) opens at about 140 F. Trial for ignition about 7 seconds, 2 tries, then lockout.
Board LEDs
GREEN steady: 12V is good (about 10 to 17 V). RED: voltage under about 10 V, or a bad ground. AMBER: the heater is running.
Red LED with a good battery means look at the ground and the wire voltage drop first.
Fault codes
E0|Outlet water thermistor open or shorted|Reseat the sensor plug. Look for water or corrosion on it. Measure ohms: a good sensor gives a steady value that moves as it warms. Open or zero: replace it.
E1|Ignition failed or flame lost at start|Gas valve open, tank has LP, igniter gap and condition, debris on the burner, low gas pressure, air in the lines. Test with a manometer while it fires.
E2|Flame lost while running|Low gas pressure at high fire, poor flame sensor or ground, vent recirculation, wind, regulator.
E3|ECO (high-limit) switch is open|Meter on the blue wires at CN9 with power off. OPEN = the ECO is bad, replace it. CLOSED = the board is the likely fault. Also find out why it overheated.
E4|Inlet water thermistor open or shorted|Same as E0 but on the inlet side. Reseat, look for corrosion, measure ohms, replace.
E5|Blower fault|Check the blower plug at CN1, debris in the blower, and 12V and ground at the blower while it runs. Replace the blower if it is jammed or open.
E6|Outlet water over 140 F for 3 seconds|Hot water is entering the heater (bypass valve passing, recirculation), or the outlet thermistor reads wrong, or the flow is very low.
E7|Linear gas valve open circuit|Check the red and white valve wires and plug. Coil should read about 80 to 100 ohms. Open: replace the valve.
E8|Air pressure switch fault|Check the hose for cracks or water, the small pickup tube for blockage, then suck gently on the hose and listen for the switch click. Blocked vent also trips it.
E9|Flame sensed before ignition or a short|Residual gas flame, a sticking gas valve, or a shorted sensor lead. Check the gas solenoid and the flame sensor wiring.
Fd|Freeze protection is active|The freeze thermostat turns on near 38 F and off near 58 F. Normal in cold weather. Drain the heater for storage.
En|Run timer ended|The 20 minute run timer expired. Close and reopen the tap to restart.
Bench tests
12V at the board while firing (above about 11 V)
Gas solenoid (brown and black): about 12 V when open. Coil about 110 ohms
Linear valve (red and white) coil about 80 to 100 ohms
Blue wires on the control panel line: about 9 to 11 V
ECO continuity at CN9 blue wires (closed is good)
Inlet gas pressure while burning, 11 to 14 in W.C.
Gallon flow test: under about 1:25
Common field failures
Reversed hot and cold lines. Low flow from a pump or filter. Single-handle faucet or outside shower mixing. Old linear gas valve converters that fail. Wasp or spider nests in the intake or exhaust. Low 12V from thin wire. Hard-water scale on the flow wheel.
Codes can look the same across brands but mean different things. Check the label: this table is for Girard GSWH-2 only.