Poor weld quality Millermatic210

[Taw Paw]

Ok guys, round #3

I have been fighting with this machine for several month on and off. Story is I purchased it new several years ago new. It worked fine for a long time. I am a weekend welder, as stated earlier in previous post the ground was getting hot. It had poor weld quality and poor penetration. I changed out the ground clamp and wire to it. Ground is not getting hot any more. But weld quality was not much better............. Then I noticed the contacts on the contactor were shot. Got a new contactor and problem got a little better. Today was welding with it and again poor weld quality with no penetration was very frustrating. So I opened the cabinet and watched the contact engage a few times. I saw a spark or two as they made contact. It also looked like the seating surfaces may be getting pitted. Is this normal for a new contactor? Does anyone have a place to start looking for the problem?

[Taw Paw]

I have attached images on the contact points on the new contactor I just had replaced. Do these marks look normal for a contactor that has less than 5lb of wire run through it? When it was replaced a few weeks ago the machine welded fine then it started doing the same thing it was doing before we replaced the contactor and the ground clamp and ground wire.

Any thoughts?

[1997CST]

I imagine it was a few more years ago than several. My tech manual for that book starts in 2001. You need to check every connection inside the machine to make sure everything is tight and not arcing. Most cables are held in place with nut and bolt. make sure the capacitors are secure to the mount. They come loose and arc and you can't see it because the screws are facing the middle plate. Check the bridge for an open diode. Check your plug on the welder to make sure it is tight and you getting the full 230. If all this is good, it maybe your gun. Does it look good? New liner? Drive motor not cranked down too hard?
When you say poor quality weld is it because it cold? Full power a bad weld? Gas problems?
Good luck