Forced Air Furnace: Fan relay failure

25 to 30 year old forced air furnace with air conditioning. Last week discovered that during A/C usage, after several minutes the fan's electric motor would stop running. Sometimes accompanied by loud "bumping" noise.
My first thoughts was the electronic thermostat, which was not the problem as the original (standard mercury analog) thermostat duplicated the problem for a test.
The problem seems to be with a power relay that is controlled by one of the wires from the thermostat and a neutral wire. My guess is the contacts for the high current relay are burned out. Several years ago I measured the fan draw at about 10 or 11 amps. (borrowed a clip around amp meter.)
-Is this relay a common DIY part readily available at a BORG, or does each maker of forced air furnace use a unique relay? -Is this relay sold only to Mechanical contractors? -Will I be on a hopeless search for finding a replacement part for a 30 year old furnace?
With the cost of gas for my car, I really cannot afford the cost of replacing the furnace and central A/C.
Please help me NOT to buy a new Furnace right now.
Phil
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Get the numbers off the relay. Check places like electrical supply houses or www.grainger.com for an equivalent. Should be easy to find something that will work.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

YOu may be able to go to a local store that sells air and furnace parts. I had some bearings go out on an old furnace and took one by the parts store and they sold me the bearings. It may help to have the part with you so they can match it up with something that will work. If they will not sell you one, then you should be able to go to a place that repairs rurnace and go through them. They may or may not charge you double the price of the part. That seems to be the standard in some places. Still beats the service call and the part.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Phil Again wrote:

Do not worry. A 30 year old furace parts are alot cheaper than a new furace parts.
--
Moe Jones
http://www.MoeJones.info
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Relays such as used in furnace aren't a DIY job. Unless you have a lot of electrical know how. There are a very few HVAC companies who will service older equipment. Make a few phone calls, see what you can find.
--
Christopher A. Young
Learn more about Jesus
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I suggest you post this to www.allexperts.com Free Advice..Hava look.
My old Coleman A/C/"electric furnace" wouldn't run when it was cold.. Ran fine in AC mode but not heat: got a horrible MOANING sound and motor wouldnt turn..smellof HOT plastic in the middle of the night. Two service guys said I needed a new motor @ $ 200 plus labor.
"All Experts" helped me replace the "start capacitor" my self for a grand total of $ 2.57 ..The original was made in the USA and lasted 16 years. The replacement at 2.50 was from China..WTH, I bought TWO. Motor is fine months later.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Thanks to all who replied.
No, the local Heating / Cooling supply house would not sell to me, or talk to me. Local contractor, who listed themselfs as Mechanical Contractors, had Yellow pages add that claimed "Well Stocked Parts Department"
Relay cost about $55.00 USD, but I am very positive is I was a H &C guy, the part would cost no more than $32.50. Maybe even less. But such is life I guess. Aside: The older guy behind the counter took one look, and pulled the replacement part off the shelf with very little hunting or glancing at the shelf labels. He called it a 90-113, and sold me an equillivant. (24013). He seemed to have several on the shelf.
Part included 4x4 mounting plate, 120VAC to low voltage (24Vac?) transformer, thermostate and load connections screw down plate, and high current relay. Easy install, exept for my sore knees. Oh, and one of the new wire nuts, yellow, from a bag of assortment of Wire Nuts, had no insides; just the plastic outside bit.
Phil
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Site Timeline

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.