Why Is My Infrared Sauna Not as Hot as It Used to Be? How to Test & Replace Infrared Sauna Heaters

If your infrared sauna has been in use for several years and no longer gets as hot as it used to, the control panel may not necessarily be the problem.

One possible cause in an older infrared sauna is a weak, damaged, or deteriorated heating element.

Some infrared sauna heaters can still produce heat even when their electrical performance has changed. This can create a confusing situation: every heater feels warm, but the sauna takes much longer to heat up or no longer reaches the temperature it once did.

Before purchasing a new infrared sauna heater replacement, sauna heating element, or replacement infrared heating tube, you can perform a basic resistance test with a multimeter.

Common Signs of an Infrared Sauna Heater Problem

• Infrared sauna is not getting hot enough
• Sauna takes much longer to heat than before
• One infrared heater is not working
• All heaters feel warm, but the sauna temperature is low
• One heater is noticeably weaker than the others
• The sauna no longer reaches its previous maximum temperature
• You are looking for an infrared sauna replacement heater because the original part is discontinued

How Does an Infrared Sauna Heating Element Work?

Most infrared sauna heaters are resistive heating elements. Their electrical performance is related to three basic values:

• Voltage
• Current
• Resistance

For example, suppose an infrared heating element is rated:

Therefore, a 120V 350W resistive heating element would be expected to measure somewhere near this value under comparable conditions.

Actual resistance can vary somewhat depending on heater construction, temperature, manufacturing tolerance, and the type of heating element. Always compare the measurement with the heater's original specifications whenever possible.

How to Test an Infrared Sauna Heater With a Multimeter

Step 1: Disconnect All Power

For the most accurate reading, disconnect the heating element from the sauna control system, or disconnect at least one heater lead so the control board and other electrical components do not affect the reading.

Step 2: Find the Heater Voltage and Wattage

Check the label on the infrared heater, heating tube, heating panel, or sauna specification plate.

You need to know:

• Voltage — for example, 120V or 240V
• Wattage — for example, 200W, 300W, 350W, 400W, or 500W

If the original heater label is missing, the specifications may sometimes be identified from the sauna model, total sauna wattage, control box information, or another identical heater that is still working.

Step 3: Calculate the Expected Resistance

Step 4: Measure the Heating Element

Set your multimeter to the resistance or Ω setting.

Place one meter probe on each of the heater's two power terminals or heating-element leads.

Do not use the ground wire as one of the two measurement points when checking the normal resistance of the heating element.

Compare the measured resistance with the calculated value.

How to Interpret the Multimeter Reading

Using our 120V 350W example, the calculated resistance is approximately 41Ω.

If the Reading Is Close to the Expected Resistance

A reading reasonably close to the calculated value generally indicates that the heating circuit is intact.

For example, readings such as 38Ω, 40Ω, 42Ω, or 45Ω may be reasonable for a heater with a nominal calculated resistance of approximately 41Ω, depending on heater construction and test conditions.

If the resistance appears normal but the heater does not produce heat, the problem may be elsewhere in the sauna.

• Failed relay
• Damaged control board
• Bad heater output
• Burned wiring
• Loose connector
• Temperature sensor problem
• Incorrect or missing supply voltage

If the Multimeter Shows OL

If your multimeter displays OL or an open circuit when measuring across the two heater terminals, the internal heating circuit is likely broken.

Current cannot flow through an open heating element, so the heater will not operate normally. In this situation, the heating element will usually need to be replaced.

If the Resistance Is Much Higher Than Expected

This is especially important when troubleshooting an older infrared sauna.

Suppose a 120V 350W heating element is expected to measure approximately 41Ω, but the actual measurement is 100Ω.

This is far below the original 350W rating.

A substantially higher-than-expected resistance reading can indicate deterioration, damaged internal connections, or another fault that is reducing the heater's effective output.

This is one reason an older infrared sauna heater may still feel warm while producing much less heat than it originally did.

Why Does My Old Infrared Sauna Still Heat but Not Get Hot Enough?

This is a very common complaint:

The important point is that a heater can produce some heat without necessarily operating at its original rated output.

For example, a normal 120V 350W heater may calculate to approximately 41Ω. If an abnormal condition causes that same heater to measure approximately 100Ω, its calculated resistive load at 120V would be only about 144W.

Both heaters may feel warm to your hand, but their actual heating performance can be dramatically different.

Multiple Weak Heaters Can Reduce the Total Sauna Output

Imagine an infrared sauna originally equipped with six 350W heaters:

If several heating elements are damaged or operating far below their intended output, the total heating capacity of the sauna can drop significantly.

The control panel may still work. The relays may still click. Every heater may still feel warm.

But the sauna may:

• Heat much more slowly
• Struggle to reach temperature
• Feel noticeably cooler than it did when new
• Perform especially poorly in a cold room or during winter

Test Each Infrared Sauna Heater Individually

If your sauna contains multiple heaters, test each one separately.

Check for a Heater-to-Ground Fault

After completely disconnecting the heater from power, you can also measure between:

• Heater power terminal 1 and ground or metal frame
• Heater power terminal 2 and ground or metal frame

The heating conductors normally should not have direct continuity to ground.

A standard multimeter will often display OL or a very high resistance.

If you measure significant continuity between a heater conductor and ground, stop using that heating element until the problem has been properly inspected.

What If All the Infrared Sauna Heaters Test Normally?

If every heating element measures reasonably close to its expected resistance but one or more heaters still do not work, the problem may be in the sauna control system.

• Failed control board
• Burned relay contacts
• Failed heater output port
• Damaged connector
• Loose or burned wiring
• Incorrect supply voltage
• Temperature sensor failure

A useful troubleshooting method is to connect a known-good heater to another heater output.

If the same heater works correctly on one output but does not work on another, the problem is more likely related to the controller, relay, power box, or wiring rather than the heating element.

Will Installing a Larger Sauna Controller Make My Sauna Hotter?

Usually, no.

If your original infrared sauna has approximately 2,000W of heating elements, replacing its controller with a 3,000W or 4,000W-capacity controller does not automatically increase the output of the existing heaters.

The wattage rating of the controller tells you how much electrical load the controller is designed to handle. It does not force a 350W heating element to become a 500W heating element.

Do Not Install Higher-Wattage Heaters Just to Make the Sauna Hotter

Some sauna owners consider replacing an original 350W heating tube with a 500W, 600W, or higher-wattage heater in an attempt to make the sauna heat faster.

An infrared sauna is a complete electrical system. The original manufacturer typically designs the system around a specific total electrical load.

This includes:

• Maximum controller capacity
• Relay current ratings
• Control board capacity
• Heater output connectors
• Internal wire gauge
• Power cord
• Plug and receptacle
• Fuse or circuit protection
• Branch circuit wiring
• Circuit breaker capacity

For example:

This is a major increase in electrical load.

If the controller, relay, wiring, plug, receptacle, and household branch circuit were designed for the original load, installing higher-wattage heaters may cause:

• Controller overload
• Relay overheating or failure
• Overheated wiring
• Burned connectors
• Damaged control boards
• Frequent circuit breaker trips
• Overheated plugs or receptacles
• Increased electrical and fire risk

The correct approach is normally to replace a failed heater with one that matches the original system's voltage, wattage, dimensions, and electrical requirements.

Where Can I Buy a Replacement Infrared Sauna Heater?

Finding replacement parts for an older infrared sauna can be difficult. Many manufacturers no longer produce their original heaters or replacement components.

Common replacement parts include:

• Infrared heating tubes
• Ceramic sauna heaters
• Carbon heating panels
• Far infrared heating elements
• Full-spectrum infrared heaters
• Quartz infrared heaters

In many cases, you do not need to replace the entire sauna just because the original heater is discontinued.

A replacement heater may be selected or manufactured based on the original heater's:

• Voltage
• Wattage
• Physical dimensions
• Mounting style
• Connector type
• Wire length

What Information Should You Send Us?

If you are trying to find a replacement infrared sauna heater but do not know the original part number, send us:

• Sauna brand and model
• Photo of the original heating element
• Photo of the heater label
• Voltage
• Wattage
• Overall dimensions
• Mounting dimensions
• Connector or wiring photos
• Photo of the sauna control panel
• Photo of the power/control box

If the original heater label is missing, photos of the sauna, control system, and remaining heaters may help identify a suitable replacement.

Infrared Sauna Heater Resistance Quick Reference

For our example 120V 350W heater:

Expected calculated resistance: approximately 41.1Ω

Important: 41Ω is only an example for a 120V 350W resistive heater. Different heater voltages and wattages will have different resistance values.

Final Thoughts: Repair or Replace Your Infrared Sauna Heater?

If your infrared sauna is several years old and is experiencing problems such as slow heating, reduced maximum temperature, weak heaters, a heater that does not work, or an OL reading on a multimeter, start by testing the heating elements before replacing major components.

1. Disconnect all power.
2. Find the heater voltage and wattage.
3. Calculate the expected resistance using R = V² ÷ P.
4. Disconnect the heating element from the control circuit.
5. Measure resistance across the heater's two power terminals.
6. Compare the actual reading with the calculated value.
7. Test each heater individually.
8. Check for possible heater-to-ground faults.
9. Replace failed heaters with properly matched parts.

Do not install a higher-wattage heater simply because you want the sauna to get hotter. The heater, controller, wiring, connectors, plug, receptacle, and household electrical circuit all need to be correctly matched.