7100 fan and over-ride switch not working during a hot fire

[79twins]

I have a 7100FP and replaced the snap disk last season. Even with the new disc, the fan comes on as it should when the firebox is heated. However, if the fire gets real hot the fan shuts down, and the manual override switch will not actifate the fan. I found that if I open the doors and use the screen, the firebox cools a little, and the fan comes back on. Any idea why the override would not work?

 

[begreen]

Snap disks come in many configurations. Maybe the new snap disk is normally closed instead of normally open. Normally closed will open when it hits a set temperature. Normally open will close when it hits a set temperaure.

 

[79twins]

The snap disc works fine on a regular fire. Comes on when the firebox is heated and goes off when cooled. But during a hotter than usual fire, the fan shuts off AND the override switch will not re-energize the fan unless the fire cools a little. I do not know if the fans have hi limit shutoffs.

 

[begreen]

That's a good question. First, check all connections to make sure every connector is firmly plugged in and not making intermittent contact.

 

[makermna74]

Yes, Quadra Fire 7100.
Thanks
Matt

 

[begreen]

As a test, I would bypass all wiring and temporarily wire the blower directly to a cord to plug it in. I am betting that it will work fine. What I suspect is happening is that there is a break in the wiring that is making an intermittent connection. This could be right at a spade lug connector, or actually in a wire, underneath the insulation. A multimeter could be used to test continuity on the 7100's wiring with the breaker turned off. Clip on the start and end of a wire segment and wiggle it to see if continuity is interrupted. That may be more work than some techs want to bother with. In that case, if the blower works fine directly wired then the wiring harness should be replaced.