Another.....Mastertemp 400 with AGS LED + Service Heater LED

JamesW

TFP Expert
Mar 2, 2011
17,457
Even if the AGS sensor is in series with the valve, the circuit board is still monitoring the AGS circuit.

The circuit board is reading the circuit as open when it's not open.

In my opinion, the circuit board logic is shutting down the heater due to a misreading of the AGS circuit.
 

setsailsoon

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Oct 25, 2015
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For this case Jame's logic is hard to question. I felt the same way when I was trouble-shooting my ignition module. Admittedly a different issue but everything in the trouble-shooting pointed to a bad module. The problem turned out to be a very slight leak to ground in the supply wires that interfered with flame sensing. Replacing the supply wire solved the problem. In this case the only thing I can think of is bad wiring as James pointed out earlier. Is there anything else that could explain this other than a bad board? I can't come up with anything other than a bad AGS and you've proven this not to be the case. Swamp's test could help improve the certainty so I'd try it. Don't see any downside... just my $.02

Chris
 

Kihon

Well-known member
Apr 14, 2008
47
Huntington Beach, CA
Well, this AM I tried @swamprat69 jumper test.
  1. Added a small wire(so I could add a jumper wire clip) inbetween the VAL wire and the VAL termal on the FENWAL.
  2. Immediately after the heater fired up, I jumped the TH terminal on the gas valve with the VAL connection wire I added. Left all other wires connected. (TH on gas valve etc)
  3. 1.25A fuse immediately blew just under the Fenwal LOL
On this test, was I supposed to disconnect the TH on the gas valve?

Added: I did check continuety between all of the FENWAL connections to the board. All good, no pins pushed out, etc.
 

JamesW

TFP Expert
Mar 2, 2011
17,457
If you want to start jumping things, you need to know exactly what you're doing or you're going to damage the system.

It's also not going to tell you anything if you're jumping out all safeties and powering the valve directly because it will just keep running no matter what.
 

Jimrahbe

Mod Squad
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LifeTime Supporter
Jul 7, 2014
15,884
Bedford, TX
K,

It the heater is still doing the same sequence that it was before you replaced the board, then I would still look at the HSI,,, See my original post #3.

Thanks,

Jim R.
 

JamesW

TFP Expert
Mar 2, 2011
17,457
What do you mean that it wasn't plug-n-play?

What was different?

When you jumped the wires earlier, did you put everything back together like it was?

Did you replace the fuse that failed?
 
Last edited:

Kihon

Well-known member
Apr 14, 2008
47
Huntington Beach, CA
K,

It the heater is still doing the same sequence that it was before you replaced the board, then I would still look at the HSI,,, See my original post #3.

Thanks,

Jim R.
No it isn't. Before i replaced it, the heater would fire up for a few secs with heat, then shut off on an AGS LED. Now it's not even firing up.

What do you mean that it wasn't plug-n-play?

What was different?

When you jumped the wires earlier, did you put everything back together like it was?

Did you replace the fuse that failed?
Not "Plug and Play" meaning that I plugged it in and it did NOT work.

Yes, everything is back together, nothing jumped. All sensors plugged in

Yep replaced the fuse that blew prior to install
 

JamesW

TFP Expert
Mar 2, 2011
17,457
The remote control connects to the fireman's switch. Just jumper the fireman's switch closed and see if that works.

Recheck the wiring connections to make sure that everything is lined up correctly.
 

JamesW

TFP Expert
Mar 2, 2011
17,457
When you turn it on at the automation, the heater goes through the startup and then goes off.

When it goes off, press the Spa On button to see what happens and then turn up the set temperature to 104°.
 

JamesW

TFP Expert
Mar 2, 2011
17,457


On the brown board in the center, it's labeled fireman's switch.

The red and green wires come from the automation.

When the automation wants the heater to come on, it connects the two wires together with a switch.

You can remove the red and green wires and jump the terminals directly.

Check the fireman's switch fuse while you're there.

Then, try the Pool On or Spa On button.
 
Last edited:

Kihon

Well-known member
Apr 14, 2008
47
Huntington Beach, CA


On the brown board in the center, it's labeled fireman's switch.

The red and green wires come from the automation.

When the automation wants the heater to come on, it connects the two wires together with a switch.

You can remove the red and green wires and jump the terminals directly.

Check the fireman's switch fuse while you're there.

Then, try the Pool On or Spa On button.
Yep just tried your idea. Removed my remote's wires, then jumped the terminals directly....didn't work. Nothing happens when I press any of the buttons. Board seems to power up initially (as in my last video), but doesn't seem to stay on tho. Turns right off.

Fuse has continuity through it. Removed it and put it back on.

One thing, the two boards physically looks different. The one hooked up is the new board, do you think this matters?

IMG_2938.JPG
IMG_2939.JPG
 

JamesW

TFP Expert
Mar 2, 2011
17,457
I suspect that they sent you a cheap generic board.

I would send it back and get the original equipment board.

Check all packaging and labels to see what the part really is.

Are there any labels on the board?

Make sure that all wiring is correct.
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
15,884
Bedford, TX
K,

I would put the old board back in and see if you still have the original problem.. If not, then you will know that something else besides the new board is wrong. The point being, if it will no longer fire up at all with the old board, then a new board is not going to fire up either.

Thanks,

Jim R.