A/C Cycling and noise under dash

My A/C compressor is cycling about every 5 seconds and when the compressor kicks on there is an audible thump coming from under the dash in the vacinity of the evaporator/blower motor. Low side pressure is 55 when compressor is off and about 38 when running. Anyone seen this problem before???

 

What's the high side? I think your pressures are jacked up for whatever reason. Fix the pressures and I think the noise under the dash will go away. Check any relays or pressure switches in the system and make sure they are functioning properly...

 

I do not have the complete set of guages, so i do not know what the Hi side is doing. I might have to bite the bullet and take it in for a proper diagnosis. I just hate to spend coin on stuff that I know that I can fix once the defective part/parts are identified.