I'm having problems with my 11 year old Mastertemp 400. I have read all threads I could find that were similar, as well as the MasterTemp "further reading" post.
The heater seems to be starting normally when the controller calls for heat. The blower spins up for 5-10seconds before the burner kicks on. However the instant the burner ignites, the SERVICE HEATER led lights up immediately. The burner continues to fire for 5-10seconds before the burner shuts off. The heater is firing - I can hear the whoosh, feel the exhaust heat up. The blower runs its cool down timer and shutoff. I found the AGS led is also lit up on the back of the control board.
I jumpered across the AGS switch, replaced the AGS switch, tested the AGS switch during the entirety of this cycle (it maintains electrical continuity), and tested both wires going to the board for continuity. I removed the header and replaced all other sensors plus the internal bypass valve and the thermal governer (because they were inexpensive, somewhat corroded, and because I ordered them before finding this web resource). I bought a NEW Board and Membrane, but swapping one or both did not fix the issue -- but oddly the brand new board does not fire up the heater at all, nor does it show AGS Error. It does power on and show the version number, but does not cycle the heater. My working diagnosis at this point is TWO bad boards. Wish I had access to a known working board in the Greater Los Angeles area, or even access to a working MT400 to try my board on....
The inside of the HX tubes have some visible corrosion, AND my reading of the Pentair MT400 Manual page 53 state: ERR AGS (or HLS): Verify water flow rate is above min (which I have with my flowmeter), Verify that inlet water temp is below 104F (it is cold water), Replace AGS or HLS (replaced both), If problem persists, verify proper operation of Internal Bypass Valve (looked fine but replaced), Thermal Governor (looked corroded, replaced) and check for Heat Exchanger Blockage. How do I check for Heat Exchanger Blockage? Perhaps I could remove the header again and try flushing water through each of the 12 pipes (seems like each right pipe pairs with a left, so maybe just test 6)? That seems easy enough, but I cannot understand how in the world the board would be able to sense a blockage immediately, especially without the AGS changing electrical state??
Would appreciate any assistance. I did call in a professional but they gave up after jumpering the AGS failed (they sent me to buy the new board, which does seem like a reasonable next step) but when that failed they referred me to Pentair's phone line, which has not got me up and running.
The heater seems to be starting normally when the controller calls for heat. The blower spins up for 5-10seconds before the burner kicks on. However the instant the burner ignites, the SERVICE HEATER led lights up immediately. The burner continues to fire for 5-10seconds before the burner shuts off. The heater is firing - I can hear the whoosh, feel the exhaust heat up. The blower runs its cool down timer and shutoff. I found the AGS led is also lit up on the back of the control board.
I jumpered across the AGS switch, replaced the AGS switch, tested the AGS switch during the entirety of this cycle (it maintains electrical continuity), and tested both wires going to the board for continuity. I removed the header and replaced all other sensors plus the internal bypass valve and the thermal governer (because they were inexpensive, somewhat corroded, and because I ordered them before finding this web resource). I bought a NEW Board and Membrane, but swapping one or both did not fix the issue -- but oddly the brand new board does not fire up the heater at all, nor does it show AGS Error. It does power on and show the version number, but does not cycle the heater. My working diagnosis at this point is TWO bad boards. Wish I had access to a known working board in the Greater Los Angeles area, or even access to a working MT400 to try my board on....
The inside of the HX tubes have some visible corrosion, AND my reading of the Pentair MT400 Manual page 53 state: ERR AGS (or HLS): Verify water flow rate is above min (which I have with my flowmeter), Verify that inlet water temp is below 104F (it is cold water), Replace AGS or HLS (replaced both), If problem persists, verify proper operation of Internal Bypass Valve (looked fine but replaced), Thermal Governor (looked corroded, replaced) and check for Heat Exchanger Blockage. How do I check for Heat Exchanger Blockage? Perhaps I could remove the header again and try flushing water through each of the 12 pipes (seems like each right pipe pairs with a left, so maybe just test 6)? That seems easy enough, but I cannot understand how in the world the board would be able to sense a blockage immediately, especially without the AGS changing electrical state??
Would appreciate any assistance. I did call in a professional but they gave up after jumpering the AGS failed (they sent me to buy the new board, which does seem like a reasonable next step) but when that failed they referred me to Pentair's phone line, which has not got me up and running.
