Pentair Mastertemp 400 (System Error: HLS error)

[kenzo42]

Hi Everyone,
I turned on my heater for the first time in 2 years and it's giving me a "System Error" red light. Looking at the underside of the circuit board, HLS led is lit.
The heater won't turn on (stays in "System Error"). There is no noise or ignition or gurgling. However, once I jumped the HLS connectors, it started right up and the heat pool light turned yellow.
Is this as simple as changing out the HLS? In another thread I read, it was the bypass valve that gave an HLS error. Thanks.

 

[ajw22]

Pentair MasterTemp Heaters - Further Reading

www.troublefreepool.com

The High Limit Switch prevents the Heat Exchanger outlet temperature from exceeding 135°F (±8°F).

The High Limit Switch is located in the lowermost well of the Manifold Adapter under the Manifold Switch Cover. Mounted below the AGS Switch, it is black to differentiate it from the AGS Switch, which is marked with a red dot.

The HLS is often caused by lack of sufficient water flow through the heat exchanger. This can be due to several things:

• Thermal regulator not opening.
• External bypass open.
• Internal bypass broken.
• Pump too small or on too low rpm.
• Clogged filter.
• Scale in heat exchanger.

The High Limit Switch is p/n 42001-0063S

Start by checking the thermal regulator. As a test remove the thermal regulator and see if the heater runs.

 

[1poolman1]

Hi Everyone,
I turned on my heater for the first time in 2 years and it's giving me a "System Error" red light. Looking at the underside of the circuit board, HLS led is lit.
The heater won't turn on (stays in "System Error"). There is no noise or ignition or gurgling. However, once I jumped the HLS connectors, it started right up and the heat pool light turned yellow.
Is this as simple as changing out the HLS? In another thread I read, it was the bypass valve that gave an HLS error. Thanks.

If the HLS error occurred BEFORE the heater fired, it is likely bad.

 

[kenzo42]

If the HLS error occurred BEFORE the heater fired, it is likely bad.

Yes, error was before it fired. It won't heat at all unless HLS is jumpered.

 

[ajw22]

Test HLS with a multimeter. It should be closed when heater is off. If it is open then replace it.

The High Limit Switch is p/n 42001-0063S

 

[1poolman1]

Yes, error was before it fired. It won't heat at all unless HLS is jumpered.

Best thing to do is to replace both the HL switch and the AGS switch. They are both in the same water and when one goes the other usually isn't far behind.
This page on Amazon will show both parts. Be sure to put the correct part in the correct port.

Amazon.com

 

[kenzo42]

Test HLS with a multimeter. It should be closed when heater is off. If it is open then replace it.

The High Limit Switch is p/n 42001-0063S

It was open (no reading) when off. I'll replace it and report back. Thanks everyone.

 

[kenzo42]

I replaced the HLS and it's fixed and making warm water. Thanks everyone.
When I was troubleshooting the heater, I spun the pressure switch every which way and have no recollection where it was originally set. Can anything be damaged if this is set incorrectly? It's an inground pool.

 

[1poolman1]

I replaced the HLS and it's fixed and making warm water. Thanks everyone.
When I was troubleshooting the heater, I spun the pressure switch every which way and have no recollection where it was originally set. Can anything be damaged if this is set incorrectly? It's an inground pool.

Too tight and the worst is that the heater won't fire. Inconvenient but no damage. Too loose and heater could fire with too little flow, or none at all in the right circumstances. This picture is how they come from the factory and how yours was most likely set.

 

[kenzo42]

It was on pretty loose where the push button was fully pressed in. However, the heater was still off. Any idea why?

 

[1poolman1]

It was on pretty loose where the push button was fully pressed in. However, the heater was still off. Any idea why?

With the pump running, remove the wires from the pressure switch and check for continuity between the terminals. The center rod should be extended to actuate the micro switch.