I found the little top overtemp breaker tripped and I reset it. Then called for heat and all worekd well for a minute. The flames were going nicely into yhe heat exchanger and then the house circulation blower came on , but this caused the flames to be pushed back into the box and sure enough it got hot and tripped the top breaker again... The air from the house blower should not be gtting in here, I suppose...
What am I facing here fellas?
Thanks ini advance
Dennis

Most likely, the heat exchanger has failed. When the combustion inducer runs, the inside of the heat exchanger is in a slight vacuum. When the blower starts, the outside of the heat exchanger becomes somewhat pressurized. Cracks or holes will allow air to leak in, disrupting the induced combustion draft. This is a potentially dangerous situation. The heat exchanger warranty should be 20 years on a GMPN - if you can locate & post the serial #, it will reveal the manufacturing date. Notice the cracks near the middle ring in the pic. In some cases the rings pop off & the clamshell halves separate, allowing air to leak in. Probably time to call in a pro.