AC Attic Blower/Blower Relay Switch

tstexJuly 21, 2014

Hello to All,

I have a Payne Unit that was installed in 2002. When I turned up the t-stat, the condensing unit went off as normal, but the attic blower continued even way past the time-delay seting.

The t-stat was set on Auto, so the attic fan/blower was supposed to turn and never did, so I pulled the breaker to the AC unit. Inside, the blower was off now. In 30 minutes, I turned breaker back on, blower in attic unit was was back on again. Turned breakers off again and left off for 2-3 hrs. Turned breakers back on, blower was on again.

So, went into the attic and found the place where the blower was in the Unit and knocked the unit and on the 5th time, the blower turned-off. From what I have read, this is the fan relay switch and the contacts are either oxidized, pitted, etc and were stuck. The jarring of the unit caused the contacts to release. The t-stat was in the auto position which means the blower was set to off if not cycling.

In 2-3 hrs later, I turned the t-stat down and the unit performed as normal and cycled itself properly. However, since this happened 1-2 yrs ago, I think it is time the relay switch is replaced.

I am going to pull the fan relay switch in the attic unit and trace the wires back to the fan motor. Of course I am going to turn-off all of the breakers to the AC/heating Unit which there are 2 of them. I found the part for $14, but just wanted to see if anyone has any advice that can make the fan relay switch installation a 100% success. I am going to take pictures of all and then draw the schematics as well. I have all of the original AC documentation/op's manuals from the installation date.

Any and all advice is appreciated. Thanks in advance.


This post was edited by tstex on Mon, Jul 21, 14 at 14:01

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What kind of relay switch you have only cost $14 ?

    Bookmark   July 21, 2014 at 5:26PM
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Here you go:

    Bookmark   July 21, 2014 at 5:54PM
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Looks fine, I did not know it is so cheap. I got one 7 or 8 years ago, cost me $50.

    Bookmark   July 22, 2014 at 11:32AM
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Thanks pfoley.

I actually queried this subject matter over the weekend on my iphone when I was at my ranch house and read a thread where you helped someone w this same topic...this is how I learned about posting on this site.

On pricing, my speculation is there are many more internet-based businesses that do not have to pay for the brick & mortar storefront, thus driving down the prices. If you combine that w great information resources like this website and others like it, you do not have to be held bondage to paying for a part tied along with the technical service.

I recently replaced a capacitor on my 5 ton condensing unit and the total drive out was $38 bucks. Since we have two 5-ton units, this compares to paying $165.00 to have the previous one replaced by a tech. I can negate having to use my dif-calculus to work the math on this one.

Thanks again,

    Bookmark   July 22, 2014 at 5:04PM
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A picture or 2 isn't a bad idea. And draw a simple diagram. Pull off wires. Unscrew relay. Replace wires. Biggest part is taking the cover off the enclosure.
I replaced one, after a "Pro" told me the system needed more return ducts! Unfortunately AC service is one of the trades with a lot of rip offs. There are a lot of honest shops out there, but a lot of the other ones also.
It's also a business where there are a lot of "Pros" that don't know what they are doing.

    Bookmark   July 22, 2014 at 7:07PM
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I agree O-40. It's hard fiding someone that always does the right thing in his business. Most of the time the resident has no clue and cannot refute the tech's claim. This really irks me when it happens to an older person w limited income.

Yes, drawings are imperative. W the advent of smart phones, pictures are great too, but sometimes they do not get all the details.

Thanks again,

    Bookmark   July 23, 2014 at 9:32AM
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Wanted to provide an update....

I am made an assumption on the fan-relay switch part and it was an error - my apologies. It was based on an older unit.

My unit has all computer boards, but there is a fan-relay part that screws into the c-board. I have to mark all of the wiring, remove 4 screws and remove the fan-relay module, then re-attach all of the wires, then screw back onto the computer board. Cost is $45-$55 bucks for the part.

Unless your unit is an older mode/style, more of the components are all computer boards now. At least this is a modular set-up to where I do not have to replace the entire board. The replacement piece does have the contacts, so this is consistent to when i slapped the plenum that housed the attic fan, it shut off when the contacts finally separated, broke the circuit and the fan stopped.

thanks to all that helped, and I really like this board..lots of good experience


    Bookmark   July 31, 2014 at 12:07PM
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I am surprised you can buy a replacement relay switch for the control board. I suppose it is a common switch that is easy to find.

You are never going to find a tech who is going to repair a board. The repair would be replace the board or the whole air handler!

    Bookmark   July 31, 2014 at 1:28PM
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over40 said "Unfortunately AC service is one of the trades with a lot of rip offs. There are a lot of honest shops out there, but a lot of the other ones also.
It's also a business where there are a lot of "Pros" that don't know what they are doing."
To which Klem replied, you can say that again! Unfortunatly AC service is,,,,,,,,,,,,,,,,,,,,,,,,, LOL
Sorry but I must find something to laugh about or else I might just take to cursing and crying over the truth in what you are saying. An all too common sight is two techs show up on a service call. #1 carries the tools from truck then watches as #2 pulls the britches off unit and pokes around inside. #2 returns to truck and talks on cell a while before returning to help #1 stare at unit. 20 minutes later #3 arrives in a secound truck and hits the ground quick stepping around house and kneels by unit while #1 & #2 look over his shoulder. #2 & #3 go to 2's truck where 3 removes one or more parts,hands them to 2,gives 2 some instructions and leaves in a hurry. 2 installs the part and unit springs to life. The dirty condenser coil and air handeler filter are overlooked,customer gets the bill and off 1 & 2 go on the way to next call. #1 just started work in the trade last week and is learning the ropes from #2. #2 got his own truck last month after watching another tech for 2 months. #3 is actually a seasoned compitent tech that is assighned service calls plus do as he did in this case,bail out the rookies as required and let the boss know how they are coming along. All three have their time billed to customer at same hourly rate but are of course paid different hourly rate by contractor. And that's part of why the bill always seems three times what it should be.

    Bookmark   August 1, 2014 at 12:19AM
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