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Emt269 · Dec 15, 2007, 08:27 AM

Have a Intertherm furnace in my mobile home that is about 10 years old and has worked fine until last year. It will cycle the blower off and on a couple times during the warming cycle until it reaches a certain temp in the house. If it is above a certain temp in the house it runs fine and works normal. I was told to replace the fan limit switch which I did with one of the same number and limits and it then was worse than before so put original back on. Have tried a couple different fan limit switches just to make sure all the times with the same results. Any help would be appreciated. Thanks.

hvac1000 · Dec 15, 2007, 12:14 PM

The fan blower control is out of calibration. Not the limit switch but the control switch that turns the blower on and off at predetermined temperatures.

Emt269 · Dec 15, 2007, 02:07 PM

OK thanks for the answer now can you tell me where to find info on how to do this adjustment? Thanks again

hvac1000 · Dec 15, 2007, 02:22 PM

It is a fixed disc and has to be replaced. It looses calibration and since it is a disc cannot be adjusted. A sfar as location intertherm usually has a metal cover that has the transformer ETC in it. Usually they are located in that box. I would refer to the wiring diagram to see which disc it is because there could be two of them and they look alike.

GrayWolf45 · Dec 15, 2007, 07:27 PM

As far as I know from my Intertherm there are three switches. One tells want temp the blower comes on and shuts off, preset at 90/130. Second one preset at 140 this is a safe guard in case fan doesn`t start will recycle the furnace. Third is located on to of the heat chamber next to the fan blower this shuts the furnace down so it dosn`t over heat, preset at 180. Also to help might want to set the themostat heat anticipator to a shorter heat cycle, meaning your furnace will run 3/4 times an hour instead of 1, your house will feel warmer ,while using the same gas usage. I also put a White Rogers fan limit switch in, there ajustable .

I have no training in this field but have had problems and had a tech out to fix mine

hvac1000 · Dec 16, 2007, 12:10 AM

Since you are in a mobile home please do not use a adjustable fan and limit switch. It voids the listing on the appliance. Mobile home furnace manufactures are controlled by HUD. Your fixed limit control temperature is set by standards the manufacturer has to be followed in order to maintain the compliance with the HUD program and for your safety

Many items on a mobile home furnace are different from a standard stick built home and that is why you will find that a standard stick built furnace is not allowed to be installed in a mobile home. This also holds true for many of the parts and any limit controls etc.

There are many reasons for this strict stand by HUD. It all has to do with UL/CSA approval agencies and the combustible type materials that surround the mobile home. To high a limit temperature in a mobile home can cause a fire since the vinyl/plastic/wood components are very close to the furnace since there is very little clearance to combustibles the way the mobile home furnaces are wedged into the cubby hole provided.

Many other parts can be used like transformers/thermocouples/motors etc. from a regular furnace. But safety devices must never be because they have a different/lower setting for a mobie home and usually have a reset button because closing off registers and dirty filters cause them to trip very easily as a safety feature.

GrayWolf45 · Dec 16, 2007, 06:11 AM

I`m not saying to exceed the manufacture settings, never do that . But at the same time the heating tech that fixed mine is specialized in mobile home furnaces.There was a period of years that Intertherm maufactured furnaces that had problems that can`t be fixed, other then buying a new unit. There is a change in air flow that causes the furanes to cycle on /off. All the above limit switch temps I mentioned are manufactured standards that come with the furanes, all the tech did was set the fan limit to come on at 115/85.
Also checked the co, which was zero in the home and 10/12 parts at the stack. I also have a new furanes ordered to install this spring.

hvac1000 · Dec 16, 2007, 06:45 AM

LSI Home,Intertherm,and Nordyne are all the same company over the years. The reason for not using the adjustable control is because it allows the customer to play with it and creating a bad situation.
The statement below is from Emt269

((ok thanks for the answer now can you tell me where to find info on how to do this adjustment?))

As you can see the first thing a person wants to do is adjust the control to see if that will make it work. This is why no adjustable controls are allowed on mobile units unless they come that way from the factory.

Will the adjustable controls work YES are they safe to use NO. That is all that I was saying.

BTW the biggest problem these furnaces have is overcoming the restricted duct system in the mobile homes. Some owners of these homes close of one or two of the registers creating more resistance in a already very restricted duct system causing heat exchanger and control failures. The cure to all of this is to keep the air filter clean,keep the A/C coil clean,open all registers, and add a larger blower motor to move more air and lessen all restrictions in the system.

Try to keep your old furnace as long as you can. The new ones do save a bit on fuel but will cost you $$$ because they have a very high failure rate. Coleman units are the worst for this. 200.00 circuit boards and 175.00 draft inducers is almost a every other year affair and you use more than the $$$ you saved on fuel just to buy the parts to keep them running. The funny part is that the restrictive duct system causes more problems with the newer furnaces that with the old.

My experience is somewhat restricted to 76 units that sit down in a camp area I own. My oldest son is in charge of the camp and does all the customer maintenance as requested. He sees many furnace problems especially with new replacement units. The Coleman rep has been out to the camp to look at some of the new installs that have problems and there is really no cure. We have stopped using Coleman for replacement and went to Nordyne which do not have near the problems of the Coleman units.

geoffscott · Nov 17, 2010, 11:09 AM

A few intertherm furnaces came from the factory around 10 years or 15 years ago with the high temperature safety shut down and the fan control thermo switches reversed. They sit side by side in the connection box and look identical. If you remove the blower, you can look down and see inside one has a shield over it. You need to change them around. The wiring is long enough to do this. Takes about 5 minutes work with a screw driver.