My Pentair Max-e-Therm 400 spa heater will not fire. I am getting a heater service light and an AGS error code. I replaced the upper limit switch according to the troubleshooting guide. I do not smell gas during the start up sequence. I tested the igniter and it checks good. Any suggestions?
Max-e-Therm 400 heater will not fire
- Thread starter Van23
- Start date
- Jul 21, 2013
- 52,714
- Pool Size
- 35000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
Max-E-Therm is the same as a MasterTemp in different packaging.
From Pentair MasterTemp Heaters - Further Reading
AGS errors are usually caused by a bad internal bypass. Too much water is bypassing the heat exchanger internally. What water that is going through is coming out too hot and tripping the AGS switch in the manifold.
From Pentair MasterTemp Heaters - Further Reading
AGS errors are usually caused by a bad internal bypass. Too much water is bypassing the heat exchanger internally. What water that is going through is coming out too hot and tripping the AGS switch in the manifold.
- Remove the leads from the AGS sensor and connect them together. Temp only for the test.
- Then, check the continuity of the sensor. It should be closed.
- Start the heater. If the sensor opens, immediately turn off the heater.
- If the sensor opens, it might be a bad sensor or the water is overheating.
- To test the sensor, put it in hot water to see where it actually opens.
- If the sensor does not open and the heater shuts off with an AGS light, the board is bad.
- May 3, 2007
- 16,934
- Pool Size
- 20000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
Just to confirm, you do not hear the flames starting (i.e. usually a big woosh with heat out of the exhaust)? If not, then it is odd that the AGS error would show up. Sounds more like a board error.
If you don't smell gas, the main valve is not opening. OR, a gas shut off before the heater may be off (closed). Have seen that many, many times. Some pool owners don't even realize one is in the gas line somewhere (usually close to the heater but sometimes at the meter).
Even with proper ignition, there is always a small amount of gas that gets out the vent before the burner lights and you can smell it. AGS switch and error will happen when the system senses there is no ignition. Replacing safety sensors and switches that are doing their job is not the key.
The AGS sensor has nothing to do with sensing ignition.
The AGS Switch prevents the Heat Exchanger output from exceeding 140° F, ±8° F (60° C, ±3° C).
If the AGS circuit opens before the heater fires, the AGS sensor or wiring are bad.
If the AGS LED comes on when the AGS sensor is closed and the wires are good, then the board is bad.
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In actual use, the AGS circuit will also trip if there is no ignition sensed by the flame sense circuit. It may not be documented, but it happens on occasion. That's when troubleshooting gets confusing.
AGS = Automatic Gas Shutoff. The system does not allow uncontrolled gas to flow into the combustion chamber and out the exhaust.
Ignition detection is accomplished by a flame sensing control system known as flame rectification.
The Fenwal Ignition Control Module sends out an A/C voltage to the sensor.
When there is a call for heat and the burners ignite, flame hits this sensor creating a “path to ground through the flame” for the A/C voltage.
When this happens, a pulsating D/C signal, in the form of micro amps goes back to the Ignition Control Module.
The flame sensor is energized with AC voltage, which is rectified to DC in the presence of flame.
The DC current flow is measurable in micro amps (uA).
On gas furnaces, 3.7 uA is a typical measurement and measurements less than 0.5 uA result in interruption of the heating cycle.
On many models, the flame current may be read at the flame current pad built into the furnace control board.
The control board converts the uA measurement to DC voltage (1 uA = 1 volt DC,).
The LED light on the Fenwal box can indicate the following problems:
www.troublefreepool.com
The Fenwal Ignition Control Module sends out an A/C voltage to the sensor.
When there is a call for heat and the burners ignite, flame hits this sensor creating a “path to ground through the flame” for the A/C voltage.
When this happens, a pulsating D/C signal, in the form of micro amps goes back to the Ignition Control Module.
The flame sensor is energized with AC voltage, which is rectified to DC in the presence of flame.
The DC current flow is measurable in micro amps (uA).
On gas furnaces, 3.7 uA is a typical measurement and measurements less than 0.5 uA result in interruption of the heating cycle.
On many models, the flame current may be read at the flame current pad built into the furnace control board.
The control board converts the uA measurement to DC voltage (1 uA = 1 volt DC,).
The LED light on the Fenwal box can indicate the following problems:
- Steady on - Internal Control Failure
- One flash - Air Flow fault
- Two flashes indicates flame no call for heat, then the Fenwal is detecting a flame current when it shouldn't be
- Three flashes indicates no flame current being sensed and ignition locked out
Heater Flame Sensing - Further Reading
www.troublefreepool.com
Only anecdotal. I've worked on those heaters since they came out 25+ years ago. Believe me or don't, I'm too old too care. Pools and their attendant equipment are weird. I said occasionally, not regularly. Would on an occasion get an AGS error with the heater not firing. Had to check deeper and find that the main valve wasn't opening, no gas smell, yet AGS light. Sometimes it takes more than blind faith on what is written to actually find the issue with these computer-operated machines.
Some issues get back to the manufacturer when we speak with their reps and changes are made that aren't documented, you just find out the next time you work on a similar piece of equipment, or see a change in the installation instructions, which I read for every piece of equipment I install every time I do it.
That's why Master-Temp and Max-E Therm heaters are now able to be used on both 120V and 240V. So many of us complained that 120V only was not good enough as many pool pads were 240V only with no neutral. That could be done with the old millivolt heaters and the light switch somewhere else. Had to make an extra trip to the customer's property to survey what we could install, rather than what we might want to install. The manufacturer listened to those of us who actually work on this stuff. Pentair changed the way their Intelliflow pumps are programmed from starting with the "off" time on timer 8 and working backward to the much easier way it is done today. Their reasoning was that they really didn't want programs for speeds 1-4, but prefer times to be programmed on 5-8. Made no sense in the real world, but one day it was different.
If the system has an AGS error, then the heater won't even attempt to fire.
This might be due to a bad AGS sensor, bad wiring or a bad board.
However, I do not think that a lack of flame sense would trigger an AGS error.
Maybe you are correct, but it does not seem logical to me.
