we have a carrier furnace with an electric pilot about 10 years old. i turned on the thermostadt the other day and there was a loud boom from the basement - when we went down, there was a strong gas smell but the blower was running and all seemed fine. about an hour later, we realized there was cold air blowing, so we shut the breaker off, turned off the furnace, let it sit and tried to restart it. as soon as we turned the breaker on the blower started running and we can't get it to stop - we tried to restart the furnace, but it still blows cold air - any ideas?