Lincoln 175HD not welding

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Hi, im new to this site so let me know if im in the wrong place.  I have a Lincoln 175 HD and the other day i was welding and i went to strike an arc, nothing happens but the normal relay click from when you pull the trigger.  Wire roller doent feed and it will not strike an arc.  The fan is running like normal and everything.  Well i took the cover off to see if anything was wrong but didnt so i put it back together and it started working again.  So i welded for another hour or so and it did it again but this time it wont start working again.  I bought it in Sept of 08 so i think its still under manufacture warranty but not sure.  I using .35 mig wire with argon gas mix.  Thanks for reading.  Im not super technical with welders but im not an idiot either so any help would be great!
Reply:There is only a 30% duty cycle on those units. You are probably tripping the thermostat switch on the diode heat sink. 035 wire @ 18 volts = about 135 amps. If the welder starts working again after 5 to 6 minuets with the fan running. you over heated it.This is not a factory defect covered by your warranty.If you can get a clamp amp meter. measure the weld current while welding. See if you can weld at 130 amps for 3 minuets straight. If so nothing is wrong. Now give it seven minuets to cool with the fan on before welding again. Think of your duty cycle this way. Weld for one minuet and give it 2.33 minuets rest.This Adds up to 3 on 7 off.
Reply:I just went out to piddle on it a little more and it still wouldnt weld, so i turned my amp switch and it started working again.  Could my amp switch be going bad?  I dont have a clamp amp meter nor do i know where to get one either.
Reply:Could be. Does your machine have a 6 position switch or a potentiometer to control the weld voltage? . (current) .  The pot is  5000 ohms. speed and  voltage controls are the same.The 6 position switches do go bad. Some times they can be cleaned, but most of the time they have to be replaced. You will need a very large soldering iron or a propane torch to replace the switch. Test a pot with an ohmmeter. You want the meter to change smoothly from 0 to 5k. and not jump around. The switch just remove the cover. get a flash light and look real close. If you had posted the code number I would know how your welder was built.Always unplug a welder if you remove the cover for cleaning and inspections.