Ac problem,vacuumed my system to neg 28,its holding that..now I need to recharge

On off cycling every 7 seconds,no oil added,a/c retro fitted from r12 to 134a fittings only ,,I don't know what a strut tower is!,,symptoms are blowing warm air and cycling constantly..I did make one mistake while recharging,using my gauges,I left the high side knob open.

So you are not using a machine to charge the system , but are trying to charge it with the store-bought cans? Kinda sounds like it's not charged enough , but without seeing it in person , I'm obviously only guessing.-----***------4/10.......was that it raytucker?

Did you evacuate the system?

Found my compressor is no good,thanks everyone.