Wire feed motor stop working. When trigger is pressed motor attempts to turn but does so in short choppy intervals. Removed the wire from feed and motor does the same thing.

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.

Could be a shorted output rectifier (diode). This would cause a lot of current pull, and therefore voltage drop (fan slowing down). The electrolytic capacitors are for dc voltage, and will blow with wrong polarity, which means ac voltage would be the wrong polarity half the time.

The contactor that controls the power to the tip (the heavy one) may be fused closed This interupts power to the primary winding if tip goes live without wire feeding.
. It may also be a shorted SCR on the control board if wire is feeding or it can also be a fused feed motor contactor- the small one.

Does it feed with the trigger plug removed from the machine? If so, then it is a circuit board. If no, then wires shorted somewhere in the gun.

relay blown in side it will be in the main unit not the wire feed if it is digatal circut bord

Check the voltage at the wire feed motor while the trigger is pulled. If there's no voltage, it's pretty safe that it's not the drive motor.
Also, with the unit unplugged, check the big power (stud) diodes for shorts.
I had a wire feed motor stop because 2 of the big diodes were shorted.

Check the voltage at the wire feed motor when the trigger is pulled.

I had a Weld Pak 100 that with 0 volts at the wire feed motor, and the problem wound up being that 2 of the big power (stud) diodes were shorted.

Try to short the trigger wire back closer to the unit or better still inside the panel somewhere. There is often a relay that is operated that allows gas to flow and power to the wire feed motor. Check where the trigger wire goes it may give you some idea. If you can identify the part you can source one and see if it worthwile repairing. Cheers

Either the trigger mechanism in the gun is bad, the servo that turns the feed wheel is bad, or you have too much tension on the adjustable tensioner knob. Take the wire out of the feed wheel, plug unit in and see if you can get the wheel to turn. If not, it is the trigger or the servo. If it turns, the tensioner was too tight.

check for power to drive motor,if power is there when you pull gun trigger then motor is bad.if no power look for bad wire connections then relay.