A DIY & home improvement forum. DIYbanter

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » DIYbanter forum » Do - it - Yourself » Home Repair
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

Home Repair (alt.home.repair) For all homeowners and DIYers with many experienced tradesmen. Solve your toughest home fix-it problems.

How do I know if furnace thermocouple is bad?



 
 
LinkBack Thread Tools Display Modes
  #1  
Old October 31st 06, 05:37 PM posted to alt.home.repair
external usenet poster
 
Posts: 7
Default How do I know if furnace thermocouple is bad?

My heat went out last year, and the HVAC company came and replaced the
thermocouple. It was cracked.

I noticed this morning that the furnace wasn't working. I don't get
that "click" when I raise the thermostat.

I checked the thermocouple. There's no obvious visible problem.

What else can I check? I really don't want to pay for a service call.
Ads
  #2  
Old October 31st 06, 06:02 PM posted to alt.home.repair
external usenet poster
 
Posts: 7
Default How do I know if furnace thermocouple is bad?

BTW, the furnace is an Amana Air Command 95. I have a digital
thermostat and replaced the batteries. No effect. No breakers are
thrown.
  #3  
Old October 31st 06, 06:06 PM posted to alt.home.repair
external usenet poster
 
Posts: 6,757
Default How do I know if furnace thermocouple is bad?

" wrote:

My heat went out last year, and the HVAC company came and replaced the
thermocouple. It was cracked.

I noticed this morning that the furnace wasn't working. I don't get
that "click" when I raise the thermostat.

I checked the thermocouple. There's no obvious visible problem.

What else can I check? I really don't want to pay for a service call.


Click from where, the furnace or the thermostat? Could be a lot of
things like a bad thermostat, a bad transformer, broken wire, bad relay,
etc.

Pay for a service call or pay for a class or two at the local tech
school to learn how to troubleshoot all the possibilities and the basic
tools needed for that troubleshooting.

Pete C.
  #5  
Old October 31st 06, 07:03 PM posted to alt.home.repair
external usenet poster
 
Posts: 26
Default How do I know if furnace thermocouple is bad?

On Tue, 31 Oct 2006 16:37:27 GMT, "
wrote:

My heat went out last year, and the HVAC company came and replaced the
thermocouple. It was cracked.

I noticed this morning that the furnace wasn't working. I don't get
that "click" when I raise the thermostat.

I checked the thermocouple. There's no obvious visible problem.

What else can I check? I really don't want to pay for a service call.

Caveat first:
I'm not a tech. I don't keep up with the latest developments.

That said, the themostats that I have used essentially connect the two
wires together that come from the boiler in order to turn the boiler
on (i.e. "call for heat"). If his happened in my house I would
disconnect the thermostat and connect those two wires to each other
directly. If the boiler came on properly then I would suspect that the
thermostat was bad or improperly set. If the boiler didn't come on I
would know the thermostat was NOT the problem. I might then check some
of the obvious things like the water feed before I called a
serviceman. I don't fix gas appliances.

Greg Guarino
  #6  
Old October 31st 06, 07:25 PM posted to alt.home.repair
external usenet poster
 
Posts: 6,757
Default How do I know if furnace thermocouple is bad?

" wrote:

Click from where, the furnace or the thermostat?


I don't get the click from the thermostat.


So take your meter and see if you have control voltage from the furnace
wires to the thermostat.

On a digital thermostat the batteries only serve to run the thermostat
electronics and maintain it's program memory, the control voltage
provided from the furnace is what operates the relay in the thermostat.

The control transformers on furnaces sometimes fail, sometimes just the
wiring from the furnace to the thermostat fails, sometimes the
thermostat itself fails. The fact that the display on a digital
thermostat seems to be working ok is no guarantee that the thermostat
has not failed.

If you get control voltage on the wiring to the thermostat (you should
be able to measure on the sub plate with the thermostat removed) it is
possible to manually short the appropriate connections to test the
furnace since this is all the thermostat does.

The wiring colors can be all over the place so if you have the manual
for the thermostat you should be able to find a diagram showing it's
connections with more descriptive language. In a simple heat only setup
there might be only two wires, a control voltage common and a heat wire.
For a heat / cool forced air setup a control voltage common, a fan wire,
a heat wire and a cool wire would be expected. It doesn't get
complicated unless you have a heat pump with reversing valves or
similar.

This link: http://home.howstuffworks.com/home-thermostat.htm has a
pretty good description on how a thermostat works and includes the
following description of the normal connections to a thermostat:

RH - This wire comes from the 24VAC transformer on the heating system.
RC - This wire comes from the 24VAC transformer on the air-conditioning
system.
W - This wire comes from the relay that turns on the heating system.
Y - This wire comes from the relay that turns on the cooling system.
G - This wire comes from the relay that turns on the fan.

If you measure between say RH and W with a meter you should read 24VAC
or close to it. If you jumper from RH to G the fan should come on,
jumper from RH to W and the furnace should come on (you should have the
fan on first). If these tests work the problem is in the thermostat, if
not the problem is further down the line.

Pete C.
  #8  
Old October 31st 06, 07:48 PM posted to alt.home.repair
external usenet poster
 
Posts: 6,757
Default How do I know if furnace thermocouple is bad?

" wrote:

Buss fuse. Woohoo!


Fuses rarely fail on their own, they are usually an indicator of a
problem elsewhere.

Pete C.
  #9  
Old October 31st 06, 09:10 PM posted to alt.home.repair
external usenet poster
 
Posts: 7
Default How do I know if furnace thermocouple is bad?


Fuses rarely fail on their own, they are usually an indicator of a
problem elsewhere.


We had some warm weather over the weekend, so I turned the thermostat
off. I asked my son to turn it back on, and I noticed that the fan
switch was set to "On" instead of "Auto."

Would the blower running continuously for a day or two be reason
enough to blow the fuse?
  #10  
Old October 31st 06, 10:05 PM posted to alt.home.repair
external usenet poster
 
Posts: 6,757
Default How do I know if furnace thermocouple is bad?

" wrote:

Fuses rarely fail on their own, they are usually an indicator of a
problem elsewhere.


We had some warm weather over the weekend, so I turned the thermostat
off. I asked my son to turn it back on, and I noticed that the fan
switch was set to "On" instead of "Auto."

Would the blower running continuously for a day or two be reason
enough to blow the fuse?


Even without knowing which fuse it was, it's highly unlikely. Any fuse
in the system should be sized for continuous operation.

Pete C.
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Purchasing Furnace - 2-Stage Variable vs. Standard pipco Home Repair 21 January 27th 06 02:48 PM
Help. Furnace improperly installed? Chuck Home Repair 11 November 2nd 04 03:26 AM
Clueless Inspector Faults Furnace Install Hell Toupee Home Repair 3 October 8th 04 07:47 PM
Furnace problems - repair, replace or ???? Paul Home Repair 11 March 24th 04 01:59 AM


All times are GMT +1. The time now is 09:24 AM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.SEO by vBSEO ©2010, Crawlability, Inc.
Copyright 2004-2014 DIYbanter.
The comments are property of their posters.