Troubleshooting guide
Suburban ST42 cold-inlet, winter-use, or not-hot-enough complaint
Use this when a Suburban ST42 or ST60 tankless water heater is not hot enough in cold inlet-water or winter conditions; Suburban's product overview says ST42 provides continuous water up to 120F where intake water is not less than 70F at 1.5 GPM, recommends ST60 below 70F or for winter RV use, and lists a 0.7 GPM minimum water flow.
Use this atlas to identify likely meaning and prepare for service. Shut off power, LP gas, fuel, or water when a listed appliance condition involves flame, gas smell, exhaust, generator shutdown, high temperature, moving jacks/slides, refrigerant, 120 VAC, control boards, repeated ignition failure, or a persistent lockout. Call the appliance maker, RV dealer, or a qualified RV technician for repair.
Owner-safe checklist
- Confirm whether the water heater label is ST42 or ST60 and record the set temperature and approximate incoming-water temperature.
- Open hot water enough to meet the ST manual minimum flow, then reduce flow or mix cold only after hot water stabilizes.
- Treat ST42 cold-inlet or winter underperformance as a model-capacity and service-planning issue, not an internal repair.
- Call Suburban, the RV manufacturer, or qualified service for repeated low temperature, LP supply, voltage protection, or installation concerns.