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Old 09-29-2023, 12:32 AM   #1
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Brand: Thor Motor Coach
Model: Chateau 24F
State: New Hampshire
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Chateau 24F, Hot Water heater not working on 110V.

The Dometic hot water heater should work on both LPG or 110 Vac. It works fine on the LPG but it does not seem to work on 110V. There are two switches on the control panel for the water heater, LPG & 110V. They can be both on or just one on. I have no indication that the 110V is working at all. Does anyone have an idea about this?
Thanks,
Jim

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Old 09-29-2023, 12:45 AM   #2
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Originally Posted by Jim Handyman View Post
The Dometic hot water heater should work on both LPG or 110 Vac. It works fine on the LPG but it does not seem to work on 110V. There are two switches on the control panel for the water heater, LPG & 110V. They can be both on or just one on. I have no indication that the 110V is working at all. Does anyone have an idea about this?
Thanks,
Jim
One of the common issues with the electric side of the water heater is the element burned out because the water heater was turned on (electric) with no water in the tank.

Also some water heaters have a switch on the water heater itself that must also be turned on.

Yes the water heater can be operated on electric and gas at the same time to shorten the time to heat water.
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Old 09-29-2023, 01:06 AM   #3
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The only indication you will get for 110vac operation is a slight buzzing near the water heater and in 15 minutes you will have hot water. I know in my 24F I can hear the buzzing when I turn the switch on.

If not, check the water heater breaker in the distribution center and make sure it hasn’t tripped. Thor doesn’t always label the breaker for reasons unknown. It is the bottom breaker on my 24F.
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Old 09-29-2023, 01:42 AM   #4
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If the breaker isn't tripped, I'm going with what EA37TS said about the burned out element. If it worked recently... that you knew for sure... have you ever turned the electric heater on with no water in the heater? If so, there's your issue.
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Old 09-29-2023, 10:13 AM   #5
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Originally Posted by Chateau_Nomad View Post
If the breaker isn't tripped, I'm going with what EA37TS said about the burned out element. If it worked recently... that you knew for sure... have you ever turned the electric heater on with no water in the heater? If so, there's your issue.
In addition to what others have mentioned be sure and check any wire nuts or other connections in the 110 VAC supply lines. It is common for a bad connection on the electric side to overheat and prevent the water heater from working on electric. If you know how to use an ohm meter you can turn off the 110 VAC power to the water heater and check if the element is open. If it is good it should have a low value of resistance about 5 to 20 ohms.
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Old 09-29-2023, 03:37 PM   #6
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My coach had the relay at the inside, back of the water fry. It looked like there was an arc at one of the spade lugs. MHSRV replaced a section of the 12 AWG hot wire and the relay during the two day PDI in the delivery barn. I replace the magnetic circuit breaker with a combination arc fault circuit breaker because I don't want a recurrence. I try to avoid the smell and smoke of burning insulation.
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Old 09-29-2023, 04:41 PM   #7
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Originally Posted by Beau388 View Post
My coach had the relay at the inside, back of the water fry. It looked like there was an arc at one of the spade lugs. MHSRV replaced a section of the 12 AWG hot wire and the relay during the two day PDI in the delivery barn. I replace the magnetic circuit breaker with a combination arc fault circuit breaker because I don't want a recurrence. I try to avoid the smell and smoke of burning insulation.
Beau, when convenient could you post a few pics of what you replaced and location, etc.? I'm thinking those are some essential parts I should add to my parts bag!
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Old 09-29-2023, 06:56 PM   #8
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Originally Posted by Chateau_Nomad View Post
Beau, when convenient could you post a few pics of what you replaced and location, etc.? I'm thinking those are some essential parts I should add to my parts bag!
The Bowden bought by Atwood, bought by Dometic water heater is a GC-6-AA. The access to the rear of the water heater is under the bedroom vanity via an access panel. Removal of the panel is required access the three quarter turn water valves to winterize the coach. On the very bottom of the back side of the water heater is the connection to the heating unit and a small, rectangular, black, plastic electrical box containing the relay for the heating element. There are 6 spade lugs: 12 volt power and ground from the coach's master control panel and 120 volt power and ground from the 15 amp CB in the coach's power center. The last two spade lugs are the output to the heating element.
Wiring instructions are on the upper left.
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Old 09-29-2023, 10:39 PM   #9
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Thanks for the instructions and pic! I'll have to look at mine to see the instructions/diagram. I hadn't noticed those before. Nice to have a heads up and be prepared!
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Old 10-04-2023, 07:03 PM   #10
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The only items that would allow the unit to run on propane but not 110V would be the element, the relay, and the 110V fuse supplying the relay. With the water heater full, turn on the unit in 110V only, check the voltage at the element. You should have close to 110V. If none, check at the incoming of the relay, if none, check your circuit breaker supplying the water heater. As another poster has mentioned, you could have high resistance in some of the connections. This would manifest itself as a lower voltage at one of these points under load.

There is also the very unlikely possibility that the 12V control wire to the relay is bad (supposed to be a yellow wire per my service manual). If you can't find the problem from the previous paragraph then check to see if you have 12V coming to the relay to pull it in. You could jumper 12V to the relay coil to test the relay.
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Old 10-04-2023, 07:08 PM   #11
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Originally Posted by PreCambrian View Post
The only items that would allow the unit to run on propane but not 110V would be the element, the relay, and the 110V fuse supplying the relay. With the water heater full, turn on the unit in 110V only, check the voltage at the element. You should have close to 110V. If none, check at the incoming of the relay, if none, check your circuit breaker supplying the water heater. As another poster has mentioned, you could have high resistance in some of the connections. This would manifest itself as a lower voltage at one of these points under load.

There is also the very unlikely possibility that the 12V control wire to the relay is bad (supposed to be a yellow wire per my service manual). If you can't find the problem from the previous paragraph then check to see if you have 12V coming to the relay to pull it in. You could jumper 12V to the relay coil to test the relay.

Actually, the most likely culprit is the control circuit board. It is a poorly made Chinese item with a very poor track record. I’ve had so many “go bad” over the years that I carry a high quality replacement from Dinosaur in my spare bag.
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Old 10-04-2023, 07:24 PM   #12
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Originally Posted by Pete'sMH View Post
Actually, the most likely culprit is the control circuit board. It is a poorly made Chinese item with a very poor track record. I’ve had so many “go bad” over the years that I carry a high quality replacement from Dinosaur in my spare bag.
The control board works with propane. So it is receiving and responding to the below cutoff temp. I would assume (although I can't verify because I don't have the board design) that the same logic for the #4 red wire to the gas solenoid would control the #2 yellow wire (with the addition of "ANDING" the white #2 white electric run input). But that is another possibility, the signal for the electric run isn't getting to the white #2 terminal.

I haven't had any problems with my igniter control board. But of course the board itself could be bad. I just feel that it is less likely since the igniter control board works on propane. I have had problems with the ECO switch but that only affects propane operation.
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Old 10-05-2023, 03:01 AM   #13
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Brand: Thor Motor Coach
Model: Chateau 24F
State: New Hampshire
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THOR #29956
Quote:
Originally Posted by PreCambrian View Post
The only items that would allow the unit to run on propane but not 110V would be the element, the relay, and the 110V fuse supplying the relay. With the water heater full, turn on the unit in 110V only, check the voltage at the element. You should have close to 110V. If none, check at the incoming of the relay, if none, check your circuit breaker supplying the water heater. As another poster has mentioned, you could have high resistance in some of the connections. This would manifest itself as a lower voltage at one of these points under load.

There is also the very unlikely possibility that the 12V control wire to the relay is bad (supposed to be a yellow wire per my service manual). If you can't find the problem from the previous paragraph then check to see if you have 12V coming to the relay to pull it in. You could jumper 12V to the relay coil to test the relay.
Thank you for your correct diagnosis. The relay was bad. I was able to home in on this myself but your astute observation is noted and appreciated. I was able to order the relay from Amazon and had it in one day!
Thank you for taking the time to analyze this issue.
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