Water Heater Control


Old 04-18-04, 10:25 PM
Thread Starter
Join Date: Apr 2004
Posts: 31
Water Heater Control

When I fire up the gas water heater in our Travel Trailer with the tempreture selector set at low the burner lites as it should but if I slide the tempreture selector over to the middle or hot side the burner shuts off but the pilot remains on. With it set at it lowest setting the water is very very hot.

I checked the owners manual and it says the lever set at left is low and set at right is high. If someone could explain this I would appreciate it.

It is an Atwood with a White Rogers control and the unit is gas only not electric.
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Old 04-19-04, 01:09 PM
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Location: The Shake and Bake State USA
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Hello: mandlay and Welcome to the Do It Yourself Web Site.

Before suspecting the problem is the control, lets start a simple diagnostic process first.

Turn off the entire heater at the control knob. Rotate it to off. Allow the water temp time to drop back the ambient temp.

Once that happens, usually a day or so later, relight pilot with temp control in the in low temp range setting. Allow several hours to pass allowing time to recoop water to selected temp.

When the selected temp is reached and the burner has cycled off, check water temp. Turn the temp select dial to highest selectable temp. Note if burner turns on or not.

If the burner fails to fire up and the water temp is very hot, over 160 + degrees or so, temp control is likely defective.

If the burner does fire up, allow it to remain on. Check water temp at a faucet at this time. Use thermometer if possible. Should be approz 110 -120 range. Note the water temp at this point.

Than allow burner to cycle off at the new temp highest setting. Test water temp. Should not exceed 140 - 160. Some temp loss may occur based on the distance to faucet, etc.

The test is to help determine if the control is defective or not. Would be of no benefit to replace a functioning control which is not the direct cause of the problem.

The manuals explaination of the selection settings are based upon a properly working control. The problem description provided may or is likely to indicate the burner is shutting off on the high limit safety device.

Test above is intended to determine the exact cause. Once you have completed the testing, use the reply button to add the updated final results of the testing. Further help can be provided.
Old 04-21-04, 03:52 PM
Thread Starter
Join Date: Apr 2004
Posts: 31
Gas water heater control

First I would like to thank you for taking the time to share your experience on diagnosing the problem. I have preformed the following test and results noted:

Turned and left unit off for 3 days before running the following tests.

1. Relighted pilot and set temp control in the low range setting, took 45 minutes and unit shut off, checked water tempreture and it was 140 degrees.

2. Turned temp selector to highest selectable setting and burner did not turn on, also tried lever in mid point and burner did not turn on.

3. Ran hot water at the faucet to displace water in tank with cold water and burner would only turn on with lever in the lowest selectable setting, Checked water tempreture after burner turned itself off and tempreture was 140 degrees.

Are there additional test which I can preform or have I diagnosed that the Temp Control is defective.
Old 04-21-04, 04:40 PM
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Join Date: Feb 1998
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Thumbs up Congratulations

Hello: Mandlay

Helping is not a problem, it is a pleasure...

Thank you for following the diagnostic testing procedure to a "T"
And for a well explained and described reply indicating the final results.
Amazing what a good exchange of information in a communication can make.

Based on the test results, 3 possibilities come to mind and may exist.

#1 Possibility)
The control is set internally to not allow any temperature above 140 to be reached. (Internally, may be the temp set tab behind the control knob.)

Behind every control knob is a tab on which the control knob is attached.

That tab is adjustable but not even a pro dares to attempt setting or resetting it. That would be a calibration. Which is not done by anyone I am aware of for liability reasons and time consumption. >>>Not adviseable nor recommendable to attempt any adjustment to the tab.<<<

Water temp max setting done so (set by the mfg) for personal safety and burn protection. Regardless of what is indicated on the control dial. Mass produced with a slight modification for the specific operating condition in which the water heater is used in.

An RV. Not subjected to long runs of piping where water temp is subjected to much cooling off during the travel in the pipes, etc.

#2 Possibility)
The control is defective. Which means incapable of obtaining a higher temp. Regardless of selector setting. (>Possible But Not Likely<)

#3 Possibility)
Somewhere in the system or the tank is or may be, a safety device which limits water temp. (>See Above, The Control Pre-setting<)

As water temp rises, so does expansion and pressure. At a higher temp the pressure or expansion may pop off the pressure temp relief valve or cause a leak to develope some where or pop a fitting in the plumbing system, etc.

If the burner and pilot remain on, (when the burner cycles off normally) and the water temp is 140 degrees at a faucet, no problem is likely to exist.

If the pilot shuts off, water heater is cycling off (shutting down) on high limit or the temperature selection control is defective. Most tanks have an internal high limit safety device. May not be so in RV water heaters.

Side Note:
Above not always so on electric water heaters used on boats. They have or may have a dual heating system. Electric coils and engine heat transfer tubes inside the tank. This option allows tank water to be heated while engine is running and or heat the water using dockside electric power.

Obtaining 140 degree water temp at a faucet, pilot remains on and burner cycles off after 45 minute recovery time (in the test results) to a water temp of 140, all is well. Indicates normal operation regradless of dial temp selection.

Based upon test results:
Your testing was done correctly. Control not defective.
Normal and proper operation. No problem exists. No defective part or parts.


Last edited by Sharp Advice; 04-21-04 at 04:52 PM.

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