I have a Intertherm Nordyne Model#MMBB-056ABHR-06 gas fired furnace with "NO HEAT". It was manufactured 12/96. The electronic control board is blinking 3 times. Also the pre-blower seems to work right and the board clicks I believe properly. What could be the problem?

You might look on the back/inside of cover for a list of what codes are indicating, when it starts through the steps it should be 1 st preblower(inducer motor,, 2nd igniter ( did you see it glow?) 3RD if igniter doesn`t come on the gas valve won`t open and burners won`t fire up,, after heat exchanger get to correct temp. then the blower fan will come on,, let us know when sequence stops

No Glow. The blower motor is always running while the furnace is "cycling". It'll run for a minute and then stop. Wait a few seconds and then run again for another minute before it shuts down again. It'll do this until I start checking the "vacuum" lines, condensation drain lines and wiggle the wiring and then it'll start up and run fine for days.
When I pull off the drain line that goes to the condensation pump, I hear a pretty strong suction coming from the part of the furnace the drain line connects to. I don't understand why it does this if this is the "drain". Is this OK?