Paloma tankless water heater won't stay on during operation.

Has been shutting off recently during showers code C813 shows up. Any clue

Has been shutting off recently during showers code C813 shows up. Any clue

Same problem. Runs for about 90 seconds, then stops running with a C8 13 error code. We turn off the unit at the remote, turn it right back on again, and get another 90 seconds of hot water. Paloma model PTG-74PVP-2, installed in September 2006. Worked flawlessly until Oct. 2011, when it began to fail occasionally, with either a C7 13 or a C8 13 error code. Now it fails each time the hot water is run for 90 seconds, unless the plumber is present. The unit is "covered" by American Home Shield's "warranty". They have sent 4 different plumbers since last October (they 'rotate' plumbing companies) and each time they have had to call Rheem, the company that purchased the original manufacturer (Paloma). The first time, Rheem told the plumber that there was no such error code possible, so he left without fixing it because it worked perfectly while he was here. The second time, Rheem told the plumber it was a propane problem, and he left without fixing it, since it worked perfectly while he was here. The third time, Rheem said the propane supply line was too small, and needed to be replaced. We had a larger supply line installed (tore up the walls and ceiling in the garage), but it continued to fail, but much more frequently. They tested the pressure (11 inches of water column) and flow rate (199,999 BTUs/hour), so we called for a plumber for the 4th time. Rheem told this guy that the flex line was restricting the propane flow, so he replaced it with a one inch flex line. AHS refused to cover the service call and flex line, because the problem was caused by an "improper installation". Apparently, the installation decays and fails after 5 years of use? On each of the 4 service calls, I told the plumber that, based on my own knowledge of electronic control systems, that I believed the problem was most likely caused by a dirty or defective combustion sensor in the unit. Each time, the Rheem "expert" dismissed the possibility of a sensor malfunction, and told the plumber not to "waste his time" disassembling the unit to clean sensors. (The unit has several sensors: combustion detection, temperature, gas flow rate, water pressure and fuel mixture ratio). At this point, I'm thinking maybe a class action lawsuit, with the purchasers of this pile of junk as plaintiffs and Rheem as the defendant, might solve the problem (or at least compel Rheem to provide schematics, test points, diagnostic information and cleaning/repair/disassembly/reassembly instructions). I think that would be fair and reasonable. Same problem. Runs for about 90 seconds, then stops running with a C8 13 error code. We turn off the unit at the remote, turn it right back on again, and get another 90 seconds of hot water. Paloma model PTG-74PVP-2, installed in September 2006. Worked flawlessly until Oct. 2011, when it began to fail occasionally, with either a C7 13 or a C8 13 error code. Now it fails each time the hot water is run for 90 seconds, unless the plumber is present. The unit is "covered" by American Home Shield's "warranty". They have sent 4 different plumbers since last October (they 'rotate' plumbing companies) and each time they have had to call Rheem, the company that purchased the original manufacturer (Paloma). The first time, Rheem told the plumber that there was no such error code possible, so he left without fixing it because it worked perfectly while he was here. The second time, Rheem told the plumber it was a propane problem, and he left without fixing it, since it worked perfectly while he was here. The third time, Rheem said the propane supply line was too small, and needed to be replaced. We had a larger supply line installed (tore up the walls and ceiling in the garage), but it continued to fail, but much more frequently. They tested the pressure (11 inches of water column) and flow rate (199,999 BTUs/hour), so we called for a plumber for the 4th time. Rheem told this guy that the flex line was restricting the propane flow, so he replaced it with a one inch flex line. AHS refused to cover the service call and flex line, because the problem was caused by an "improper installation". Apparently, the installation decays and fails after 5 years of use? On each of the 4 service calls, I told the plumber that, based on my own knowledge of electronic control systems, that I believed the problem was most likely caused by a dirty or defective combustion sensor in the unit. Each time, the Rheem "expert" dismissed the possibility of a sensor malfunction, and told the plumber not to "waste his time" disassembling the unit to clean sensors. (The unit has several sensors: combustion detection, temperature, gas flow rate, water pressure and fuel mixture ratio). At this point, I'm thinking maybe a class action lawsuit, with the purchasers of this pile of junk as plaintiffs and Rheem as the defendant, might solve the problem (or at least compel Rheem to provide schematics, test points, diagnostic information and cleaning/repair/disassembly/reassembly instructions). I think that would be fair and reasonable.