Fan Blower Relay or Fan Limit Control?

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  #1  
Old 10-02-04, 11:35 AM
Josh G
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Old Furnace, Blower won't stop

I have a furnace that is the original. Our house was built in 1978. The blower stays on regarduless of the heat setting being set to off. I mentioned it in here at the end of last winter, and got the advice to hit the side and see if it would stop, and it did! This website was in many conversations that week. Anyway, it seems the magic has come to an end. We just fired it up again for this winter, and now the fan stays on, and the old "hit me with your best shot" does not work anymore. I remember one of the moderators saying it was a temporary fix, but I can't remember what the problem was and if it is fixable. could you remind me what I need to do to fix it. the info on the unit is below,

BDP company (emblem on the front says PAYNE)
model number- 518A030CC
Product Number- 518A00O3OOOOAAAA

Thanks for your help!
 
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  #2  
Old 10-02-04, 05:52 PM
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Hello: Josh

I may have been that moderator which suggested you slap the side of the furnace and the fan blower would shut off. A trick often used to help determine if the fan blower relay and or temp switch is stuck closed.

Doing that side slapping jars the fan relays internal contacts, which allows them to open, breaking the electrical current flow to the fan blower. The internal contacts used in fan temp on/off switches (relays) becomce pitted over the years of usage.

The pitting is normal wear and often causes the contacts to stick together. The slap simply jars them loose but does not solve the problem. Replacing the fan on/off switch (relay) resolves the problem.

To accomplish removal, unplug the heater or turn off the electrical power to it. Locate the relay (fan on/off switch) and remove it. Usually only two screws secure it once the cover plate is removed.

Two wires are usually but not always attached to the switch. Note which wire goes where prior to removal. Take that part along with the brand name, model and serial numbers to any local appliance store and or heating parts retailer to obtain a new replacement part.

Install the new switch exactly as the current one is or according to the manufacturers instructions included with the new part. Be sure every step is completed during the re install prior to plugging the unit back in to the power source or turning on the circuit breaker.
 
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Old 10-04-04, 02:04 PM
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Not sure just what control you have there . Check out the schematic there on the unit 78 you could still have a fan limit control there in the unit and not a board. if you do just get a new one like it If so just kill the power to the furnace put the new one in . set it to the same fan limit ### just like the old one.

ED
 
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Old 10-04-04, 11:41 PM
Josh G
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What am I looking for???

Sorry for the simpicity of this question. This is all a little new to me. I opened up the furnace, and found three things that could be the relay. One is outside of the main electrical box and has two wires connected. (one black, one white) it has a dial/button that is accessible from the outside of the housing, and there is a sticker next to it that says "Aulillary limit control- to reset push button on the control firmly. If failure continues call a service man." Then inside of the box that the control wires from the thermostat hooks to is basically two components. One has five wires connected to it, and it looks like some kind of coil. In fact it says "coil" on the tag on the front. Then there is one more component that has 4 wires connected, and it simply has some voltages printed on it. There are a few other items, but they don't look like they are switches. Are any of those I described in the ballpark of what I am looking for??
Thanks again,

JOSH
 
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Old 10-12-04, 09:28 AM
Josh G
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Fan Blower Relay or Fan Limit Control?

I posted here a few weeks ago about my blower running continously, and I got two responses, So I finally got around to looking into my furnace, and I found that the two responders were talking about two different parts. One said to replace the Fan Blower Relay, and the other said to replace the Fan Limit Control. I assumed they were talking about the same thing, but according to the parts guy, they are two seperate things. Is there a way to test either of them to see which one it is?? Thanks for your time.
 
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Old 10-12-04, 10:15 AM
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Need info info here just what do you have there for heat and cool .Electric, GAS, LP, OIL. How old is it ? When you talked to the parts guy didnt he know what was not working.

 
  #7  
Old 10-13-04, 09:40 AM
Josh G
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more info...

Sorry about that, It is original to the house (bulit in the late 70's). It is a gas furnace. The brand is Payne. It has a "control box" that has three components in it. One has a coil, about 4 wires. I believe it is the relay. There is one that has two wires and a reset button. It looks like it could be the limit control. The other component has 4 wires, and they are not removeable. Parts guy wasn't much help in troubleshooting. He simply told me what he had for my machine.
 
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Old 10-13-04, 10:28 AM
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Hello: Josh

I found the original first post you made on the subject and combind the two into this single thread. Doing so keeps all replies and communications together for easier reading and following along.

Some furnaces use a combination of seperate controls, sensors and or switches combind into one part. Some furnaces do not combind parts. Each is a seperate part.

Different terms are used to describe any one of them as a seperate unit or a combined part. Some call them componets when used as a combination of parts or componets when seperate parts are used. All of which only adds to the confusion but that is the way it is in the entire industry.

When I read your latest new post yesterday and the mentioning that someone posted how to stop the fan from running continously, I figured it was me. Sure enough it was me.

I used the term relay and or temp on/off switches because of the part term confusion. Some use relay and some use fan switch. If I caused the confusion or part of the confusion, kindly excuse me.

Whichever part is used on that furnace, it is very likely to be the cause of the problem. And for the reason noted. If the contacts on the part of the switch that extends into the firebox become pitted with usage and age, they tend to stick together. Slapping the furnace oftens jars them loose.

But that slapping on the furnace is not a cure. Only a temporary solution. The part (by whichever name or term is used to describe it) must be replaced. Once the contacts are pitted they cannot be fixed.

Best way to determine where that part is, is to follow the fan motor wires from the motor up to the part. Turn off lectrical power or unplug the heater and remove the part the wires are connect to.

With part in hand and brand name, model and serial numbers, go to any local parts store and buy the new part. (Piece, componet or whatever it is or called by name) Install it exactly as the existing one is and problem should be resolved.

Suggestion:
Make a hand drawing of how each wire is now connected to existing part. Install the new replacement according to the wiring diagram you made or those provided by the mfg, whichever applies.

If the furnace is still the original, the exact part may not be available but a replacement generic type is. Install per mfg instructions. Generic types come in several varieties to yet further add to the confusions.

Most generics are called time delay relays. These types do not respond to temperatures inside the firebox. They do not even have probes extending into the firebox. They turn on based on a time delay upon t-stat activation.

How is all that for confusions? You are not alone in all these confusions either. Happens all the time and daily here to. The calls coming here about part terms and part names from techs as well as customers never stops...
 
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