Real post: Rheem heater fan won't shut off, need advice

I have been having an intermittent Rheem air conditioner/ heater problem. The blower won't shut off unless I cut the main power. The furnace shuts off fine. Switching off the fan or anything on the thermostat won't shut it off. The technician says that they won't repair it unless they find it dead. By the time the technician arrives the AC is working again because it usually fails at around 1-4AM then resumes working again at 5AM.
I am now deciding to replace the parts myself but need some help. I'm not certain but I think the symptoms point to the blower relay D7 or the fan cycle control switch F7 on this schematic diagram
http://www.freewebs.com/acrepairs/RHEEM.jpg .
Where is the fan cycle control switch is located in the Rheem heater - is it inside the furnace?
Thanks Tim
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
http://r1.bloodwars.interia.pl/r.php?ra200
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Mordred9 wrote:

Spew: http://groups.google.com/groups/search?enc_author=QZeh5hgAAAAapPVIiht1O8nWYb99WDrgfTNsojGn4glfauzClCMSmQ&scoring=d&filter=0&num 0
mailto: snipped-for-privacy@telekomunikacja.pl abuse@ telekomunikacja.pl
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Tim Zeifer wrote:

Don't know the Rheem brand but usually it's the fan/limit module either being set too low for the shut-off temp or the module is broken. Considering that it's cold this time of the year the chance that it's broken is high. This link seem sto explain it pretty well:
http://toad.net/~jsmeenen/blower.html
--
Regards, Joerg

http://www.analogconsultants.com /
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Do you mean the fan that circulates the air through the house, assuming it is a forced hot-air, cold air furnace?
There is a switch that controls when the blower is on, in the heating cycle, that keeps the blower running until the plenum temperature goes below a certain level so that as much heat as ppossible is extractred. If that switch contact is physically sticking, the blower will run continuously. But you indicate turning the main power switch off and then back on fixes the problem, so unless there is mechanical vibration when you cycle the power, there is something else going on.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
hr(bob) snipped-for-privacy@att.net wrote:

IIUC some of those fan/limit controls have an internal pre-heater and then it can happen that the contacts finally let go when that pre-heat has vanished because the power was cut.
--
Regards, Joerg

http://www.analogconsultants.com /
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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.