Pentair MasterTemp 400 AFS Light on

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JamesW said:
If the blower is not running correctly, then you're going to have an air flow fault.

I would figure out why the blower isn't running correctly.

Go through the blower test procedures and check the capacitor.

Don't run the heater with damaged wires. Something can short out or spark, which is not safe with a gas heater.
Click to expand...

can it be something as simple as a bad air flow switch?
 
If the airflow switch is stuck closed, that might be making the circuit board conclude that the airflow switch is defective.

The circuit board looks for an open switch before the blower starts. If the switch reads as closed before the blower starts, the switch is bad.

Is the airflow switch open or closed with the blower off?

Does the airflow switch close when the blower starts?

Does the blower run at full speed when it's on?
 
JamesW said:
If the airflow switch is stuck closed, that might be making the circuit board conclude that the airflow switch is defective.

The circuit board looks for an open switch before the blower starts. If the switch reads as closed before the blower starts, the switch is bad.

Is the airflow switch open or closed with the blower off?

Does the airflow switch close when the blower starts?

Does the blower run at full speed when it's on?
Click to expand...

Is the airflow switch open or closed with the blower off? - I dont know - how do i tell?

Does the airflow switch close when the blower starts? I dont know this either

Does the blower run at full speed when it's on? The only time it goes on it when I jumped it and it didn't go full speed
 
With the wires removed from the airflow switch and the wires not connected together, measure the resistance from one terminal of the airflow switch to the other terminal.

Before the blower starts, the contacts should show as open. Use a digital multimeter set to ohms. The reading should be O.L (Open Line).

Once the blower starts, the contacts should show as closed. A digital multimeter should show 0 to 1 ohms. You might need to power the blower directly to check this.

You can get a digital multimeter at Lowe's, Home Depot etc.

Since the blower isn't running correctly, check the capacitor. If it looks bad, replace it.

You can get a multimeter that measures capacitance. Look for one that can measure up to 100 microfarads. Get a multimeter that says "True RMS".

Measure the capacitance of the capacitor to make sure that it matches the capacitance rating on the label of the capacitor.

Do the other tests as described in the other referenced thread.

Note: Don't do anything that you're not sure that you can do safely.
 
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JamesW said:
With the wires removed from the airflow switch and the wires not connected together, measure the resistance from one terminal of the airflow switch to the other terminal.

Before the blower starts, the contacts should show as open. Use a digital multimeter set to ohms. The reading should be O.L (Open Line).

Once the blower starts, the contacts should show as closed. A digital multimeter should show 0 to 1 ohms. You might need to power the blower directly to check this.

You can get a digital multimeter at Lowe's, Home Depot etc.

Since the blower isn't running correctly, check the capacitor. If it looks bad, replace it.

You can get a multimeter that measures capacitance. Look for one that can measure up to 100 microfarads. Get a multimeter that says "True RMS".

Measure the capacitance of the capacitor to make sure that it matches the capacitance rating on the label of the capacitor.

Do the other tests as described in the other referenced thread.

Note: Don't do anything that you're not sure that you can do safely.
Click to expand...

last question (i think) for you and AJW- if you had to buy another heater - which brand would you buy? this thing is old and if the service person can't fix it, im going to break down and get a new one.
 
I think heaters are a commodity. None of them stand out with reliability. They live in a harsh environment and get attacked by weather, critters, and chemicals. My MasterTemps have held up well over the years. I would get that or a Raypak.
 
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JamesW said:
With the wires removed from the airflow switch and the wires not connected together, measure the resistance from one terminal of the airflow switch to the other terminal.

Before the blower starts, the contacts should show as open. Use a digital multimeter set to ohms. The reading should be O.L (Open Line).

Once the blower starts, the contacts should show as closed. A digital multimeter should show 0 to 1 ohms. You might need to power the blower directly to check this.

You can get a digital multimeter at Lowe's, Home Depot etc.

Since the blower isn't running correctly, check the capacitor. If it looks bad, replace it.

You can get a multimeter that measures capacitance. Look for one that can measure up to 100 microfarads. Get a multimeter that says "True RMS".

Measure the capacitance of the capacitor to make sure that it matches the capacitance rating on the label of the capacitor.

Do the other tests as described in the other referenced thread.

Note: Don't do anything that you're not sure that you can do safely.
Click to expand...
look what I found -

Looks like two of the wires are completely chewed through. Could this be my problem?
 
Henry121083 said:
look what I found -

Looks like two of the wires are completely chewed through. Could this be my problem?
Click to expand...

Looks like some critters found their way into your heater. Check for what other wires may be chewed,

That is likely one of your problems They may have created other problems.
 

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Henry121083 said:
im wondering if this is why I have power to the heater, but not the blower
Click to expand...

Is the black power plug in your heater?

Is your heater connected to 120V or 240V?

You look at the picture in Figure 20 showing where the plug goes? The unused plug is usually left sitting in the electrical box.
 
ajw22 said:
Is the black power plug in your heater?

Is your heater connected to 120V or 240V?

You look at the picture in Figure 20 showing where the plug goes? The unused plug is usually left sitting in the electrical box.
Click to expand...

I looked at figure 20 on page 30.

I believe it's 240v since this is the plug that came out of it. I didn't see any other plug in there. I'd imagine when they installed the heater years ago they threw it out since it's a 240v system

On page 30 figure 22, that looks like the other side of this 12 pin connector. My guess is that since this has power running through it and two of these wires are severed while others aren't it makes sense why some parts of the heater are getting power (like the touch pad) and some aren't.
 
The BLACK plug is for 120 volts, the RED plug is for 240 volts.

If your plug is damaged, you need a new plug.

It can definitely cause the problems that you are having.

Turn off the power to the heater and check everything.

Replace any damaged pieces before restoring power.
 
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JamesW said:
NOTICE: Installing the black 120 volt plug in the control box and then connecting the heater to a 240 volt line will destroy the transformer, control broad, and ignition control module, and will void the
warranty.

If you install the red 240 volt plug and then connect the heater to a 120 volt line, the heater will not READ THE FOLLOWING CAREFULLY:

1. Check the line voltage to your heater. This heater will operate on either 120 Volts AC or 240 Volts AC.

2. Remove the covers and check the 12-pin plug in the back of the control box. The plug must match the voltage in the heater circuit.

3. If the 12-pin plug is not plugged into the back of the control box, select the correct plug from the bag in the control box and plug it in.

The BLACK plug is for 120 volts, the RED plug is for 240 volts.

If your plug is damaged, you need a new plug.
Click to expand...
plug is damaged - it's a 240v that came out and I'm getting a new 240v to go back in. I'm just speculating if this is my problem or not
 
Henry121083 said:
plug is damaged - it's a 240v that came out and I'm getting a new 240v to go back in. I'm just speculating if this is my problem or not
Click to expand...
It's definitely a problem.

It might be the only problem, but there's no way to tell for sure until you replace it.

Check thoroughly for any other damage and replace anything as needed.
 
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