furnace blower stuck running

I've a gas furnace of unknown make, model and have an AC installed as well. It connects to a thermostat through a four wire configuration. The whole setup is about 13 years old. The thermostat have three settings like the average thermostat. A/C(Red, yellow and green shorted), heat(red, white and green shorted) and there's a switch labeled auto/on that let's you turn on the blower manually(red and green shorted).
Every once in a while, furnace blower keeps running after turning off after using fan only and only when I use fan only. I thought it was a problem in the thermostat, so I pulled it out of the socket. Fan continued to whir.
I measured the voltage across green and red and read 24V as the fan continued to run, so it's clear that there isn't a short in control wiring.
To shut it off, I'll have to short red and green a few times with a paperclip at the thermostat socket and fan eventually turns off.
If I don't do this, it contiues to run forever. I can also do the same shorting technique to get the blower stuck running. My assumption is that pulsating the control terminals turns it off by jiggling the stuck terminals apart.
Is there anything I should suspect beside the mechanical relay?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
If there's a relay to control the fan motor, then that's the problem. Sometimes the control is solid state, but in any case, that's where the problem is.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

You should suspect that we can't tell you anything about your system without seeing it. Make/model/serial numbers help, but still not enough information. You shou should also suspect that you will find a local, *competent*, licensed, professionally trained, HVAC technician in your Yellow Pages.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
X-No-Archive: Yes
Noon-Air wrote:

If my intention was to make someone else rich, I would have already done so. Thanks for your pointless advise.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

You wanted advice, you got advice, you didn't like advice, too bad... The reason you got that advice is from your post the problem is obvious and it should already be fixed. since you apparently can't see that; you should put down the meter and call a tech like he said. This is not a slam it is meant to help. some of the things you can destroy playing with it like a toy could cost substantially more.
Joseph <'//><
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I guess he failed to read my sig file
--
Steve @ Noon-Air Heating and A/C
snipped-for-privacy@comcast.net
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Oh, bright one, tell me how in the hell that the fan/limit control is going to fix this guys problem.
Be very specific, so we can tell how it's related to the relay that is likely going BAD!
Oh, you can't tell us.........eh? Then STFU!!
Goodbye. :-)
-- kjpro _-~-_>_-~-_>_-~-_>_-~-_>_-~-_>_-~-_>_-~-_>_-~-_>_-~-_>_-~-_>_-~-_>
( kjpro @ starband . net ) remove spaces to e-mail
Want it done yesterday? Or done right today, to save money tomorrow!!
_>_>_>_>_>_>_>_>_>_>_>_>_>_>_>_>_>_>_>_>_>_>_>_>_>_>_>
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Yet another:
"I second that!" STFU!!
wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I didn't say what he did was smart, I was just commenting on your childish response.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Consider this "drivel", *anybody* that messes with a safety limit switch that obviously doesn't know what it is or what it does, needs to get his head examined.... because now not only has he voided *any* warrenty that might be on his furnce, but has also voided his homeowners insurance. You must have been blessed at birth to be able to take chances like that with your home and your family's lives.
The advice I gave is correct, and I still stand by it. If you choose to ignore it, then the consequences are on you.
--
Steve @ Noon-Air Heating and A/C
snipped-for-privacy@comcast.net
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I'm gonna have to agree with Mike...why would the mortgage company require the insurance if it didn't protect them against owner's stupidity? Also, how would the investigator be able to tell an adjustment wasn't made by a "local, *competent*, licensed, professionally trained, HVAC technician in your Yellow Pages".

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Just as an aside....how many auto policy claims would be paid if "stupidity" was a legitimate exclusion?? ;-))
ms

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Could be a couple of things. You need a meter. If no meter call a tech.
TAB Dude
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

In favor of the OP.
Read the post again.........he measured the 24v across the stat wires. So, I believe he'd have to have a meter. :-)
-- kjpro _-~-_>_-~-_>_-~-_>_-~-_>_-~-_>_-~-_>_-~-_>_-~-_>_-~-_>_-~-_>_-~-_>
( kjpro @ starband . net ) remove spaces to e-mail
Want it done yesterday? Or done right today, to save money tomorrow!!
_>_>_>_>_>_>_>_>_>_>_>_>_>_>_>_>_>_>_>_>_>_>_>_>_>_>_>
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Your right... A Good multi meter. The conditions you describe is indeed a control issue, but most likely not your t-stat. you will need a meter that will do milli amps. At best you will isolate the fault, see a burnt contact and say "Oh!". More likely you will narrow the problem down to two possible issues. At this point you will call atech or change parts. If you have a $10.00 analoge meter from Sears, it will not do. Happy hunting!
TAB Dude
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
.Clueless garbage about an unknown unit snipped.

Let your fingers do the walking and locate someone in your area that knows what in hell he is doing?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Sorry for the snips and dip.
In respnose to THIS:
If my intention was to make someone else rich, I would have already done so. Thanks for your pointless advise.

start already.

Sounds old already, most AC units have thermostat wire running to the equipment. We are still working on wireless stats.

So you saying you have a dead short between R-Y-G standard circuit for cooling? If it was short then it would be off, hence "short".

shorting..I hate short's, how bout you?

Oh yeah , thats what I would have done...

transformers..uh....24VAC
Oh yeah, Thats would I would have done.....

That the best diagnosis I have heard all week. Nothing Pulsates, jiggles, or sticks, if you have well maintained equipment. Someone answered you're question:
Noon-Air wrote:

If my intention was to make someone else rich, I would have already done so. Thanks for your pointless advise.

No you need to call someone in the phone book under"A", for Air Conditioning. Or what I should do is tell you what's wrong and let you spend twice the amount of money at Radio Shack and Home Depot?
Have a nice Day? Oval
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    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.