Originally Posted by doogee
Sounds like the system needs more bleeding to me...
+1, if it is the heat that is going on and off, and the blower remains constant.
If the blower is turning on/off or weak at lower fan speeds and blows hard on high then its likely your final stage unit.
If it is intermittent, even on full, and you have a digital climate unit, you may need to replace a resistor inside.
If those two fail then you may need a new blower. You can test the blower directly using the plug to your final stage unit. Research the pinout; I diagnosed a final stage unit failure by jumping the terminals. You should be able to test every speed of the unit. Don't leave it jumped too long, it takes a lot of amperage so the wires/jumpers will get hot quick.