Troubleshooting A Fogatti Tankless Water Heater That Won't Power On

Updated 04/23/2025 | Published 01/16/2023

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Digital Multimeter with 42" Long Test Leads - LED Display

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Question:

Fogatti tankless water heater has 12v power but nothing getting to the control panel any ideas

asked by: Ray

Expert Reply:

The Fogatti RV Tankless Water Heater # LSB64FR has a switch located inside the unit to the left of the exhaust vent. If this switch is off the unit will not operate. There's also a fuse right below it that you'll want to check before turning the unit on.

If the fuse is fine and the switch is on and the unit still isn't powering on then you'll need to test the power wire at the unit with a multimeter # PT89ZR to see if maybe you're not getting a full 12v to the unit. If you're getting less than 12v then either your power source (battery) is the issue or you're experiencing voltage drop and will need to increase the wire gauge running between the two.

You'll also want to check your ground wire and ensure that it's running to bare metal (preferably the chassis) and is secure.

If you've checked all this and still can't get it to turn on then let me know and we can keep troubleshooting.

expert reply by: Kevin C

Wire Diagram
(click to enlarge)

Fogatti On Off Switch
(click to enlarge)

Carolyn

2/26/2024

I have tried everything you suggested and I still can't get it to turn on ...help!

Kevin C.

3/5/2024

@Carolyn Is your wall controller turning on or giving you any kind of error codes? Did your previous water heater run off of 120v power and if so did you possibly connect to that same power wire? if the electrical side is fine then the next step is to check the water and gas but you'll typically get an error code on the wall controller if either is out of tolerance. Can you send some pictures of your controller and the face of the unit with the door open?

Kirsty

3/11/2024

@Carolyn We just had the same issue... we googled everything and also rang jayco. All we needed to do was press the button on the app.. and it worked straight away. It's the intellijay app and it controls everything Hope this helps Kirsty

Kevin C.

3/12/2024

@Kirsty In your case the power running to the unit was shut off by the power management system and you changing it in the app allowed power to flow to the unit. @Carolyn this could be the same issue you're facing and can be checked by testing the voltage running to unit with a multimeter # PT89ZR. If you have no power running to the unit then we know either a power management system isn't turning the power on or the power source isn't charged enough power the unit.

See All (9) Replies to Carolyn ∨

Eric

3/21/2024

Have done all these steps and still no hot water . And the control panel won’t light up

Kevin C.

3/29/2024

@Eric If your wall thermostat isn't lighting up then it's not receiving power. You can check the voltage at the thermostat with a multimeter # PT89ZR to see what it's getting. If you let the two thermostat wires touch while the main unit had power then it's most likely fried and you'll need to reach out to the manufacturer for replacement.

Kevin

4/5/2025

@WhatW what should the voltage b on thermostat wires coming off of the unit. My thermostat isn't coming on at so

Jerred H.

4/5/2025

@Kevin 12 volts. You can check it with a multimeter like item # PT89ZR. Do you have power running to the water heater? Have you checked your ground or looked for a blown fuse?

Sindy

4/29/2024

MY THERMOSTAT IS ON AND IT HOW THE DEGREE BUT IT WONT SHOW THE SHOWER SYMBOL .

Kevin C.

4/29/2024

@Sindy The shower symbol will only appear on the thermostat when water is running through the unit to point of use. You'll need to ensure that the unit has enough water pressure, gas pressure, and 12 volt service and can then open a shower faucet valve to activate the system.

Garrett

4/30/2024

I’m having trouble with my hot water heater. I have 12v/gas/water. I have no power to the controller when wired up. I have wired up two blue wires to the controller, black to positive and white to neutral. Ground wire I have on a screw on the backside of the frame. Any ideas?

Kevin C.

5/1/2024

@Garrett Use your multimeter # PT89ZR to test the voltage at the main unit. If you're not getting 12 volts on the black wire then you'll need to check for a blown fuse between the battery/DC distribution panel and the water heater. Next you can check the fuse in the main unit (pictured above) to see if it's blown and make sure your switch is in the on position. If you ever had power running to the unit and touched the two blue communication wires together that will fry the system unfortunately. If this isn't just a simple break in the power somewhere along the line then you'll most likely need to reach out to Fogatti for either a new control board or new wall thermostat.

Garrett

5/2/2024

@KevinC Thank you for responding. Once I turn on the unit I have a voltage drop from 12 to 8. The blue wires never came into contact to fry the controller. I’ve reached out to fogatti and they are not easy to work with.

Kevin C.

5/2/2024

@Garrett A voltage drop under a load means that you're getting a lot of resistance (ohms). You can measure the resistance with a multimeter # PT89ZR and should really only be getting about 1 ohm. If you're getting more than 1 ohm then I recommend increasing the gauge of the wire ran for the power wire.

Darren S.

6/21/2024

I have a no start situation brand new heater. I have 12 V going to the unit. The switch is on the fuse is good. The ground is good. I don’t know what else it could be.

Kevin C.

6/21/2024

@DarrenS If you've confirmed power is running to the unit, the switch is on, and the fuse isn't blown then the control board is likely defective and you would need to reach out to Fogatti for a replacement. If the communication wires for the wall thermostat touched while the unit was powered it will fry the control board and ruin the unit.

Steven

8/19/2024

@KevinC hey I may have hooked up to the 120v hook up from my old unit and blown the fuse. Is board fried is there any to test the board with multimeter

Kevin C.

8/20/2024

@Steven If you hooked up to 120v and fuse blew that may have protected to controller but you'll need to reinstall a new fuse in order for power to ever reach the controller. From there you could test the power wire running to the controller and the output to see if power is coming in and out but honestly if you install a new fuse and the unit isn't working then the controller is likely blown so I would wouldn't even bother testing the controller to see if there's power. I would reach out to Fogatti and see what they can do to help replace the controller if needed.

See All (9) Replies to Darren S. ∨

Bruce A.

10/11/2024

I have power to remote I think it not sensing water flow . No codes .

Kevin C.

10/14/2024

@BruceA You could potentially have a bad water flow sensor. This is located just above the drain tube. You'll need to reach out to Fogatti though because this isn't a part that we currently offer a replacement for. It's a little odd that you're getting no error codes though so you might have a control board issue instead. Either way I would start by contacting Fogatti to get the ball rolling for a warranty repair/replacement.

Thomas

12/24/2024

Hello, ok I have black to + and red to - and 2 blue wires to controller i went right to battery i have power to control er but it won't come on please help

Kevin C.

12/26/2024

@Thomas You have your positive and negative wires backwards. The red needs to be your power and the black needs to be your neutral/ground. I've attached a diagram above showing this. You'll probably be fine but you might have blown the fuse as well since you had the polarity reversed. Swap those wires over and let me know if it doesn't start functioning.

Thomas

12/26/2024

@Kevin on the back of the water heater it show black + and red - should I still do it red to red

Kevin C.

12/27/2024

@Thomas No, if you have actual confirmation that the black is your positive then there's no reason to do anything different. I would check that your ground is going directly to the trailer/motorhome's frame. In your other comments you stated you have 12v power when touching the blue wires and black wire, but when you test the black and red you get nothing. This tells me the ground your unit is connected to might not be the best.

See All (4) Replies to Thomas ∨

Thomas

12/26/2024

Ok hello, on my unit the black wire is + and the red wire in - , it is a FS08B1 fogatti, any ideas?

Kevin C.

12/27/2024

@Thomas For that model the manual lists that the black wire is positive and that you should have a white wire for your negative. I've run into this a few times with Fogatti where the factory doesn't follow the wire color scheme that the manual states. I would leave your blue wires connected to the thermostat and then disconnect the red and black and flip them to see if that solves the issue.

Thomas

12/27/2024

Well you were right, even tho the back tells you to put black on+ and the red on - they are wrong, I put the red + and the black to - and it works now thank you for the help.

Kevin C.

12/27/2024

@Thomas No problem, Fogatti should have labeled correctly to begin with so that the end user can actually install themselves.

Thomas

12/27/2024

@KevinC yes so pass it on to everyone 5hanks again

Zack

2/25/2025

@KevinC hey man I just bought and installed the fogatti instashower 8 plus. Mine came with a black and white power wires. My 12v supply is yellow + white - and I hooked it up yellow to black and white to white. It powers on and the controller lights up but thats it. no icons on the bottom of the control panel. tech said I needed minimum 50 psi that can't be true. I have 40 psi at my current spicket and around 2.3 gallons a minute out of my hot side. being the wires are black and white in what world would white be positive. Will it still click when you switch it on and the controller light up with reversed polarity?

Kevin C.

3/3/2025

@Zack The manual I'm seeing online is showing that the 8 can accept a range of water pressure from 14.5psi to 150psi so I doubt that you'd need 50psi just to get it to work. 50psi would definitely be preferred but the water heater should still run at a slightly lower capacity at 40psi. The manual also states that the black wire should be your positive and the white would be your negative. If you reversed the polarity it should blow the internal fuse to protect the unit so you wouldn't be able to flip the wires and see if it would work. I would double check that the plug was removed from the water inlet. I've seen some units where the plug is fully inside of the inlet without a portion sticking out so if you weren't paying close attention it's easy to not see it and still hook up to the water line. From there I would double check the gas pressure to cover your bases. If it still isn't kicking on and giving you the shower or heating symbol when faucet is on there might be an issue with the sensor at the water inlet, which would require reaching back out to Fogatti to get a replacement.

See All (5) Replies to Thomas ∨

Hey H.

2/12/2025

Hey Kevin, I have a fogatti tank less water heater and can't get the thermostat to turn on. I have 12v at the fuse, the outside switch is on, I do not have propane but shouldn't it still light up?

Kevin C.

2/14/2025

@HeyH It would still light up and give you an error that it's not getting propane so you're losing power somewhere in the wiring or the thermostat is faulty. Is this a new install or has this been in use and is now having an issue? Did you touch the two blue communication wires together while connecting it to the unit? If so it will fry the circuit board for the thermostat.

Christina

3/17/2025

Hi there, I’m having trouble with my control panel. I can get the physical control panel to start up and show the temperature, but I can’t get any of the bottom row of symbols to show up. The fan won’t kick in so the fan image won’t appear, and it’s not showing the shower on the system either when I have the shower going at full blast. I’ve checked the gas line, water line, and reset the breaker on it, and I don’t get any error codes. What else do you think it could be?