Home heating problem


I have a problem with my home heating system. The heat works fine when it decides to come on. I have a digital thermostat that is set for different temps throughout the day. At times the system works great and at other times it fails to come on when the house temperature drops below the minimum temperature the thermostat is set to. I've tried to manually turn the fan on the heater to the "on" position but it won't come on that way either. The heating system is close enough to the thermostat that I can hear the fan attempting to come on but it doesn't seem to be successful. I've replaced the thermostat thinking that it might be a problem with that. Also, the heater seems more likely to come on after it has been off for a while. Any help or knowledge would be greatly appreciated.
-Jason
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I'd have a pro check it all out. Furnaces can be complex and finicky. Already you've replaced a thermostat and have that expense.
(No, I'm not in the business ! Two things I can't do, furnaces and soldering that doesn't look like it was done by someone with Parkinson's)
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jasone wrote:

Perhaps the bearings on the blower motor are sometimes freezing up, especially when running has heated them up and caused some expansion. A little lubrication might help.
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Digital thermostats are computers. Read your manual and you will be amazed about the modes they offer.
If that does not do it, you need a service call.
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Gas? Oil? Could even be an almost clogged air filter ... learned that when I did a lot of dusty work in the basement last winter. Gas furnace "tried" to fire up, but wouldn't. Clogged air filter ... an easy fix. Also on the new furnace installation, one worked fine, the other not always. After lots of replacement parts were thrown at it ... under warranty ... one tech notices ... this wiring harness should be shielded ... checked against the other furnace ... sure enough ... there had been an upgrade that my failing furnace did not have. So electrical noise from the furnace was tripping it into a fail mode. And that's been my experience with failing gas furnaces.
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start with the manufacturer's manual and then work your way thru these links:
http://www.arnoldservice.com/Troubleshooting_Heating_Problems.htm
http://www.misterfix-it.com/Solutions/5Air.html
http://toad.net/~jsmeenen/wiring.html
jasone wrote:

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