Help!

[hardingj]

I just bought a house that as a pool, the pump is on the side of the house. There are three handles that I assume control the jets, skimmer, the suction for the Barracuda but I don't know which one controls which. The pressure on the pump registers 20 psi but there is not enough suction to get the barracuda moving and the jets don't put out much pressure either. If I unplug the barracuda and put my hand over the intake under the water it builds up enough suction that I can plug the barracuda in and it will run for a few seconds before it stops. I am guessing that something may be clogging one of the pipes going from the pool to the pump. Is it ok to run a "snake" through the pipes to try to unclog any blockage? How can I tell which of the three handles control what?