Raypak 106/156a Heater Parts Diagram

The Raypak 106A outputs 105,000 BTU and is designed for above-ground pools and smaller spas. The Raypak 156A outputs 150,000 BTU — roughly 50% more — making it a better fit for larger above-ground pools, spas, and smaller inground pools that need faster heat-up times. Both models share the same copper fin tube heat exchanger design, stainless steel tube sheets, and built-in automatic bypass, but the 156A adds an AFT digital control panel with a microprocessor-controlled thermostat and self-diagnostics, while the base 106A uses an analog dial thermostat.

This is one of the most common issues on the 106A and 156A. It typically means the control board is not detecting a flame signal after ignition. The most likely causes are a dirty or misaligned flame sensor or rod, a weak pilot flame not fully covering the thermocouple, gas pressure that drops below the required 11 inch WC during ignition, or a loose/corroded wire connection between the pilot assembly and the ignition control module. Clean the flame sensor, verify gas pressure holds steady during startup, and check all wiring connections before replacing the control board.

A Sensor Failure error on the Raypak 156A usually points to a problem with the thermistor (temperature sensor) or high limit sensor. Common causes include a loose connector, corroded wiring, or a failed sensor. If the display also reads -50 degrees F, this indicates an open circuit on the thermistor — meaning it is either disconnected or has failed. Try unplugging the sensor connector for a few minutes to reset the control board, then re-seat the connection. If the error persists, test the sensor resistance with a multimeter or replace the thermistor. Part number 009577F is the OEM replacement thermistor for these models.

Start by verifying 120V is reaching the unit and that the on/off switch is functioning. Next, check the transformer — it should output 24VAC on the secondary leads (blue and yellow wires). If you have 120V in but no 24V out, any open safety sensor (high limit, pressure switch, or thermal cut-off fuse) in the circuit will interrupt the 24V signal to the ignition module. The thermal cut-off fuse (part 005899F) is a frequently overlooked culprit — it is inexpensive and fails without any visible sign. If gas is present but the pilot won't light on a new installation, air trapped in the gas line is the most common cause and must be purged before the heater will ignite.

The Raypak 106A and 156A use a copper fin tube heat exchanger. If you have a leak or are losing pool water through the combustion chamber, a damaged or corroded tube bundle is usually the cause. The tube bundle (the copper coil assembly inside the exchanger) can be replaced on its own — the 106A uses part 014874F and the 156A uses part 014875F — without replacing the full heat exchanger assembly. A full exchanger replacement (014869F for the 106A) is only necessary if the header, tube sheets, or housing are also damaged. Replacing the tube bundle alone is significantly less expensive and is the recommended first repair for leaks.

Poor water chemistry is the leading cause of premature heat exchanger failure on gas pool heaters. Raypak recommends maintaining pH between 7.3 and 7.4, total alkalinity between 120 and 150 ppm, and calcium hardness between 200 and 300 ppm. Maximum salt concentration should not exceed 4,500 ppm and total dissolved solids should stay below 3,000 ppm. Water that is too acidic will corrode copper tubes, while high calcium causes scale buildup that reduces heat transfer efficiency and can crack tubes over time. Keeping chemistry balanced is the single best thing you can do to extend the life of your heater.

Both the 106A and 156A include a built-in automatic bypass valve that regulates water flow rate through the heat exchanger. This eliminates the need to manually adjust flow when pool pump speed changes. More importantly, the bypass helps prevent condensation inside the heater caused by cold water entering the exchanger too quickly, which can lead to sooting, scale buildup, and premature corrosion. If the bypass valve fails or sticks, you may notice the heater running inefficiently or producing excessive condensation. The bypass valve (006716F) and bypass dam/shaft kit (006717F) are both available as OEM replacement parts.

The interactive parts schematic on this page maps each component of the Raypak 106A and 156A to its labeled position on the heater (for example, 1C for the high limit sensor, 4H for the tube bundle, 1M for the pressure switch). Click any labeled part on the diagram to view the OEM part number, current stock availability, and pricing. You can then add it directly to your cart. If you know the part number from your owner's manual or a service technician, you can also use the search bar above the diagram to look it up by name, label, or part number.