I have a goodman 5 ton ac unit. Everything seems to be running except the blower fan motor. The motor seems to be pulsating like the voltage is pulsating. Any idea what may cause this?

if no voltage from control board check safety circuit if ok bad control board

On your control card for your furnace check the fan motor taps for power supply with a multimeter for having the proper voltage. Most control cards have two wires to control fan speed in heat mode and another speed for cool mode operation. You can locate the normal wire colors on the control schematic (electrical drawing) to see if the wires are connected properly.

If your motor has been wired improperly you may have already damaged the windings in the motor and you will need to replace the motor. It only takes about a minute at the wrong voltage to burn a motor up.

You may have a bad capacitor. Most fan blower motors operate at different speeds in heat mode than cool mode and get their voltage applied to different windings in the motor to get different speeds. Most windings need a capacitor to get current and voltage back in phase to increase efficiency, but if the capacitor is bad the motor can run in one mode and can even reverse direction in another mode.

Sounds like I just figured out your problem, get a new capacitor.

Is it the original size motor? It sounds like it could be to many CFM for the size of the duct causing back pressure when the blower goes into high.

check your themostat fan mode switch to see if it in on or auto. It should be in auto. If this does not stop indoor fan motor, (it may take up to 2 minutes for the fan to stop, preprogrammed shutoff in the thermostat and fan control cards may make you think the fan has not stopped ) If this does not stop the fan the fan control board in your air handler has a green wire shorting to 24 volt signal in the theromostat wire or the contact on the blower control card is stuck and will need replaced.

check for proper voltage from the transformer to the blower to see if blower is recieving voltage. check continuity on motor windings.....open loop indicates windings are shot

This is a 2.5 ton unit. The 30 in the model # stands for 30K btu's which equals 2.5 tons. How many square feet is your house and is it insulated?

That does not sound normal at all, I have a Goodman Heatpump and the Fan on the Evaporator (outside unit) should run as soon as it starts up!
The only delay you should be seeing is when the unit starts, the fan in the AHU starts 5 seconds after and runs for about 1.5 minutes after shutdown.

they would need to change the coil indoors to a 3 ton. If the blower speed can be increased it should be fine.

Motor, wiring and/or capacitor. If the sticker on the side of the motor isn't burned off you can get the motor info off that. Model numbers from the motor do little for locating the motor but my help. Best thing to do is get the AC motor specs and look up online (cheapest) or go to a motor shop. The specs you need would be as follows.
Horsepower-Such as 1/4 or 1/3
Voltage-Most likely 240/1 (240vac single phase)
Rotation-CW/CCW looking at the shaft end of the motor
Amps
Frame size

You have a voltage bleed somewhere or a short, whatever you want to call it. Do you have a control board on this unit where the relays are integrated into it or do you have the old type where the relay is separate? Anyway, you need to take a meter and take voltage readings to the motor when it's acting up and when it's running right. I have had the same problem with a Goodman unit before and it turned out to be the tstat! What I would do is remove the cover off the tstat and take a small jumper wire and touch the r terminal to the y terminal. If the motor starts right up, you know it's the tstat. If you have the same problem, then the only thing it can be is a low voltage short to the unit from the tstat, bad control board if you have one, or a bad relay. But if the unit is working fine in heat, it's probably not the relay. I hope this helps.