I'm working on an American Standard furnace model # TA02224C17581605AP, I have replaced the high limit switch and the furnace works for a couple days then it stops heating and the fan just keeps running. The people try to run the house on 90 thinking it will warm up quicker. Can you help ?

You will have to follow the Voltage and see where it is open, maybe a bad high limit.

Why was the high limit replaced? Was this a problem before replacement, and did replacement have any impact on system operation? If the previous limit failed & the current one is acting up, the unit is overheating. Replacing the limit control is treating the symptom, but not solving the problem. Check for an airflow restriction of some type (clogged air filter, clogged a/c coil, etc.).

Thank you for your help, I found the problem. The switch was shorting out on the furnace housing and blowing the fuse on the control board.I will have to go back and clean and service the furnace, that might help it run too.