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Tapping on fan relay starts cycle of furnace. Do I need a new relay?

I've had three HVAC's to test my furnace. Furnace often will not come on. It sometimes will run correctly after tapping on fan relay switch. One HVAC said I need a new sequencer. Another said to replace the fan relay switch, since it heats and runs after getting it going. I'm aty a loss, both money and patience. Who is right???

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Seems the relay would be the cheaper of the two ideas to try. You should be a ble to check the relay more easily with a small light bulb and see if ti is working

Posted on Feb 17, 2012

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Posted on Jan 02, 2017

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SOURCE: furnace will not turn on in Auto mode thermostat

It sounds like you T-Stat is messed up. Look in your manual to see if there is set up instructions. If not I would change the T-Stat.

Posted on Jan 03, 2009

solveditnow
  • 39 Answers

SOURCE: (HVAC) Furnace Not Igniting Quickly

Make sure a back draft in the flue is not happening. Wind can blow it out until the flue heats up. The flame sensor may not be close enough to the burner flame. It may be weak and need to be replaced or if its an optical one it may be dirty and not see the flame very well. Its not wasting much gas but it puts extra wear and tear on the gas controls, is noisy, and, as you said, blows cold drafty air. A gas control system that has issues of any kind is not real safe. It needs to get fixed.

Posted on Jan 08, 2009

Sea Breeze
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SOURCE: troubleshooting intertherm feh-015ha (FROM FREEZING FAMILY)

Having changed the fuse and breaker tell me there is a major short in you furnace. 240 volts is a lot of amperage and a very delicate job to attempt to help you directly. I have found that any intertherm dealer near you will be happy to help solve your problem. Yes, the sequencers are possible reason but 50 amps at 240 volts is what concerns me. Did your transformer burn out also?
Let me know what you think and if you would like, I will locate the correct source of help. Thanks, JT

Posted on Feb 03, 2009

james3751
  • 614 Answers

SOURCE: Intertherm furnace/AC, fan on the furnace won't shut off.

How old is the intertherm. The old ones have fan limit switch and sometimes they stick. The new ones have a fan baord or time delay relay. They go bad from moisture and they just go bad sometimes. It sounds like you just have a shorted relay. If you think you can replace it you can get a relay at any parts store. Need the model number of unit. If not just call a service tech for free estimate. Russ

Posted on Jul 24, 2009

  • 288 Answers

SOURCE: sequencers keep breaking down on RUUD heat pump

the control voltage for the sequencer should be 24 volts. that needs to be checked. also the sequencer is a switch that allows current to pass through them and are rated at particular volts and amps. If you are having and overcurrent situation, then it may burn them up. this one is tricky because and overcurrent should burn up the fusable links at your heating elements first. I would have these voltages checked and make sure only one sequencer per heating element. the low voltage side may be wired in series but the line voltage should be parallel or not sharing the 240 volts

Posted on Dec 15, 2009

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Gas furnace short cycles 2 minutes or less. Multiple troubleshoot steps and replaced components - no help. Any advice?


I did not see that your indoor fan motor started. Near your indoor fan motor there is a temperature switch that is called the fan delay relay. On a temperature rise the relay shuts a contact that turns on the indoor fan motor. If the contact does not close the high temperature limit will shut the gas controls off like your getting. A fan delay relay also allows the fan to run a minute or so to carry away the remaining heat in the furnace and help cool the furnace down. The fan delay relay is normally mounted in a recessed area in the fire wall of the furnace plate. I have also seen them on the top of the furnace heat exchanger. Anyway, the fan delay relay will probably not be available on a sunday, so temporarily until parts are available, try turning the thermostat fan from auto to on and try the furnace again. By turning on the fan to on the high temp limit will not shut you down again.

I have had high temp limit change there trip points, but you said you bypassed it and did the same thing.

Another cause could be using the wrong type of air filter. The new pleated filters sold block to much air flow. If air mass flow rate drops the difference in temperatur go up and when the difference in temperature go up, it gets nearer the high limit and causes it to trip. All pleated filters drop normal air flow through ducts by at least 35%. To make your air duct system work properly use the what is called throw away filters which cost about 1/3 the cost of the pleated filter. Remember to either clean or change the throw away filter monthly to reduce dirt being drawn into your duct system.
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Low speed is controlled solely by the furnace itself. Depending on the age and brand of the furnace it is either brought on by time or temperature.

From your description of "tapping the relay of the limit switch" I assume you have an older furnace with a combination fan/limit control. The most common of these were a grey box with a removeable rectangular lid. In some cases there was a (commonly white) switch poking through this cover which you could manually turn low speed on if you pushed it in, make sure it is pulled out.
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....After your thermostat has been satisfied and the flame shuts down...you can physically watch that dial move clockwise and hopefully reach the setting of around 105, unlesss that setting is set below the temperature of the room the furnace is in (try setting this setting higher to see if it helps).
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How old is the intertherm. The old ones have fan limit switch and sometimes they stick. The new ones have a fan baord or time delay relay. They go bad from moisture and they just go bad sometimes. It sounds like you just have a shorted relay. If you think you can replace it you can get a relay at any parts store. Need the model number of unit. If not just call a service tech for free estimate. Russ

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