My furnace will not light due to an open pressure swith or limit control switch.
How do I check this switch and remedy the problem.

You are asking professional how to bypass designed safety switches. I suggest that you contact your heating technician. Sorry, good intentions only go so far. One of my grizzly duties is forensic studies of heating systems gone bad. It's sad what people have rigged up to try and get by for a night and not calling a professional. Most never woke up!

Just a homeowner here.

I had a similar problem and found that if I jumped them with wire, then I could use that to narrow down which was open. Back to what therinnaiguy said, it was very tempting to just leave the swicthed jumped "just for the night" so my family could get some sleep, but those control points are there for a reason.

I found that blowing/sucking into the pressure switches a) helped me confirm the switch worked and b) unstuck the stuck one (at least for a while).