cooler terminal plug on 325ext??

[Rambozo]

Another option is to just use a computer/monitor extension cable. Either locally at a good computer shop, or from online source. That way you get a nice molded plug and either make your cooler with the appropriate jack, or just cut off the end and wire it right to your cooler/switch. Amazon has a ton of options here is a link to them from 1 foot to 15 feet.

http://www.amazon.com/gp/product/B000067RRX

Also I understand your not wanting to trip a breaker, but having a cooler switch kinda defeats the purpose of having the cooler plugged into the welder. Sure they would go off together, but the big problem is forgetting to turn the cooler on, not forgetting to turn it off. That is a quick way to smoke a torch power cable in short order. I know for me it would just be a matter of time. I would try a new breaker. Nuisance tripping a 50 amp breaker doesn't seem right, even with inrush current. Breakers are made to handle short periods like that, but at the price they now sell them, I would bet that QC on them can't be very good, so try another new one and see if that helps.

[performance]

You know, I was thinking...and it dawned on me what you are doing. Don't do it.
The outlet on the back of our machines is not designed for anything but our coolers. The wires running to the outlet are very small and designed for very light amperage draw of our coolers. Using something that draws more than a couple amps 220V can pose a real hazard. That is one reason we use the plug that we do, so people don't try to plug in something they shouldn't.

[WhitsonMetal]

How many amps is safe? The motor I have is 2.5 amps at 220V. I actually did find a monitor extension cable, chopped the end off and completed the wiring. Tested everything and had no issues. Also, I have a lighted switch built onto the front of my welding cart, the process would be welder on, switch on- switch off, welder off. It's no more inconvenient than reaching around for the switch on the back of the machine.

[Rambozo]

How many amps is safe? The motor I have is 2.5 amps at 220V. I actually did find a monitor extension cable, chopped the end off and completed the wiring. Tested everything and had no issues.

From the Everlast Power Cool W300 page:
Specifications

Input Amps: 1.1
Input Voltage: 240V
Input Frequency: 50/60Hz

So you would be over double the current. If you want to play it safe, you could use a relay to switch the cooler. As a bonus, you could use a time delay relay so it doesn't come on exactly when the welder starts, but slightly later.