I have a Lennox Pulse furnace. It's making a

high limit switch, no proof of flame.

Limit switch. Call a technician :)

Check the circuit board to see if the little 1 amp car fuse is blown, if it is replace it, if not, check to make sure the furnace is on and the door switch is engaged. if that doesn't work call a proffesional to come diagnose the furnace.

What is the model number? I have an SLP98 (installed on 11/29/2011).... and if I take the cover off the front of the furnace the panel that has the fancy "Lennox" badge on it) you will see two clear round windows about the size of a half dollar (one high on the furnace box and one lower on the blower box.) If you look downward into the window on the blower box you can see a red LED display that will sometimes flash error codes like E228 (one character at a time). If your model has something like this, let me know. I've done some DIY fixes recently out of necessity....and their easy.....and several technicians confessed they didn't know much, if anything, about the newer high effieciency Lennox gas furnaces.

you will need to verify voltage from the board to the inducer. If you have the installtion manual there is a flow chart for the sequence of operation of the furnace.
The basic sequence is:
1. thermostat calls for heat
2. inducer motor starts and runs for a pre-set amount of time
3. the pressure switch closes and allows for ignition trial
4. ignition is proved back to the board allowing the system to operate.

Verify 120VAC to the inducer motor upon call for heat from stat, if you have 120 at the leads that connect to the inducer and it does not start , the motor is faulty. If the inducer starts use a voltmeter across the pressure switch terminals, a voltage reading of 0 VAC will verify contact closure and ignition should occur.

The pulse furnace was under a factory recall due to breaches in the heat exchanger, unfortunately for you, the Lennox Corp. has ended the program that allowed for an allowance / furnace for replacement. To test the heat exchanger a special kit is required from lennox that will verify integrity of the heat exchanger. (If the heat exchanger seal has been comrimised the pressure switch will not prove and the igniton sequence will be interupted and cause the system to go into "lock-out" mode).I know this is probably not what you wanted to hear. Hope this helps, please list as "very helpful" if it did

If this is a high eff model, check to make sure the intake vent is not plugged.

MAYBE the module. If you call for help be sure they know how to work on a Pulse or they're likely to just tell you to replace the furnace (try to find a company that was a Lennox dealer at least 10 years ago). The Pulse is a very different animal that many in my industry don't understand and are quick to fault - the Edsel of the heating industry.

Make sure to check and see if you do not have any bare wires touch ground or if you have any wires pinched causing a short to ground. Safety first so turn of power before checking. Also check to see if any wires on unit are touching one another. Hope this helps you.

when you tighted it it very well could have done damage to the motor or you could have it off kilter 1 of the 2