On a 30A air cooled spool gun, why is the wire feed motor not turning?

If the wire feed on your Hobart 251 MIG welder won't stop when you turn it on, there could be a few possible causes. Here are a few things to check:

1. Check the trigger on the MIG gun: Make sure that the trigger on the MIG gun is not stuck or damaged. If the trigger is stuck in the "on" position, it will cause the wire to continuously feed.
2. Check the wire feed motor: The wire feed motor could be faulty or jammed, causing the wire to feed continuously. Try disconnecting the wire feed motor from the welder and see if the wire still feeds. If it does not, then the motor is likely the problem.
3. Check the wire spool: Make sure that the wire spool is installed correctly and is not jammed or tangled. If the wire is not feeding smoothly from the spool, it could cause the wire to feed continuously.
4. Check the wire feed control settings: Ensure that the wire feed control settings are set correctly. If the wire feed speed is set too high, it could cause the wire to feed continuously.

If none of these solutions resolve the issue, it may be best to contact a qualified technician or the manufacturer for further assistance.

The only things that come to mind after your checks are a spool not set in completely, a stripped spool or a spool drive shaft failure of some kind.
so...make surenthe spool is not stripped, its seated all the way and if so is the drive shaft for the spool and/or feeder pulleys all moving. If nothing is moving anywhere but you hear the actuator motors turning inside you have a warranty issue.

Had the same problem with mine but mine isn't miller and don't know if your's is built the same but if you access the inside of the machine there's there's a large copper spool inside and that wire feed handle is powered through it. The connection heats up over time and becomes a short. I re spliced mine then soldered it and then cut piece of copper tubing and crimped it around the connection and soldered that as well.
Corrected the problem and I tried pretty much all listed solutions other then this first. Tried the new liner in the torch, the new tip and clamping the wire feed assembly with a clamp instead of the tensioner. All failed. I stumbled on to the fix accidentally when I was trying to install a more heavy duty fan. Hope this helps. Good luck.

Could be the welder, the gun motor, the wiring, ect. Does the drive roll turn without any pressure?

do you have the right size tip ?

the spool gun is a 12volt motor, i usely hook it to the power feed for the feed motor in the welder. it is also 12 volt . i have heard of some welders that have 110 volt feed motors but have not seen one yet but just to be save i would test the power feed to the feed motor before i made the connection.

The control box for the spool gun it's just an adapter to feed the right voltage to the wire feed motor, the heat (voltage) must be adjusted from the three knobs:
1) Process Contactor knob must be dial on wire feeder CV using remote.
2) Polarity Must be set on DC
3) Voltage, depends on thickness of your work piece and wire gage, but 20 volts must be enough for up to 1/4" thickness and 035 4043 aluminum.

I never heard of a 50A spool gun, probably you meant 30A.

If your voltage it's erratic check the following:

Clean and tighten connections both inside and outside unit.

Check and secure lead connections to remote control.

Be sure connection to work piece is clean and tight.
Remove excessive coils from weld cables.

If continues to be too high (hot) and can't control it, then you should send your machine to be checked that's probably a problem with the PC1 or PC2.

If this was useful to you please vote. Thank you and good luck.

Sounds like the wire driver circuit, or drive or motor is faulty. Probably a blow driver transistor or chip. But may be a motor brushes if it has any?

Take the spool off of the machine and see if the feed wheels turn. If they do, you probably have the wire stuck in the tip or the line leading to it -- replace as necessary. If they don't turn, there is something jammed at the feed rollers or the motor that turns them. My bet would be that there is something stuck in the lead to the gun or the tip. The whine noise is probably the rollers slipping on the wire. Since the wirewill not feed, the spool doesn't turn.