Problem with Miller Challenger 172

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I have been working with a Miller Challenger 172.  I was working yesterday and then all of the sudden, the welder stopped feeding wire.  I figured that I had blown the drive motor fuse so I unhooked it and checked and it turns out that someone had gotten in there and replaced the fuse with a 15 A circuit breaker (which by the way had not been tripped).  I buttoned it back up and let the fan run for 30 mins or so and still would not get anything but a click-click from the relay closing and opening a second later.  I still have juice because it will spark still, just not feed and the gas comes through fine as well.  As a side note, I have been suspecting a problem with the drive mechanism because it would be slow to start feeding at lower wire speeds.  Am I going to have to replace the drive motor on this thing or is there something else that might be causing the problem?  Where is the best place to get the parts to fix it -- someplace online or should I just take it to a local shop to get fixed?  Thanks,Chris
Reply:There are many Miller dealers, check your yellow pages. It is easier and much faster to either call them or the Miller help line to find out your issue. Take this from me, who has done computer repair for 16 years and I still get the occassional call that someone expects me to fix their computer, with a hardware issue,  magically over the phone.

Miller phone - 920-734-9821John -  fabricator extraordinaire, car nut!-  bleeding Miller blue!

http://www.weldfabzone.com


Reply:

Originally Posted by chdorseyI have been working with a Miller Challenger 172.  I was working yesterday and then all of the sudden, the welder stopped feeding wire.  I still have juice because it will spark still, just not feed and the gas comes through fine as well.  As a side note, I have been suspecting a problem with the drive mechanism because it would be slow to start feeding at lower wire speeds.  Am I going to have to replace the drive motor on this thing or is there something else that might be causing the problem?  Where is the best place to get the parts to fix it -- someplace online or should I just take it to a local shop to get fixed?  Thanks,Chris
Reply:Chris, you should give Miller a call at the phone number that Micro posted, 920-734-9821. I called them on Monday and a very nice lady answered the phone who then transferred me to Tech Support. I spoke with an extremely knowledgable man by the name of Doug. I explained the problem in detail and what checks I had made to determine that the problem was not with the wire feed motor. He told me the first thing to check was the heat selector knob, to make sure it was on one of the numbers and not halfway between them. With that being done, he then told me to check the "Contactor" assembly located directly under where the printed circuit control board is mounted. He stated that this part will wear out over time and is considered a "consumable". I looked at the contactor on my 172 and noticed there was carbon deposits on the contact points. Making sure my 172 power cord was UNPLUGGED, I cleaned the contact points using a can of professional grade electrical contact cleaner, then used a small, thin flat tip screwdriver to knock the carbon deposits off the contacts. The type of electrical contact cleaner that I used DOES NOT contain any form of lubricant and when it drys it leaves no residue behind. DO NOT use TV tuner contact cleaner as it contains a lubricant, which could cause problems in your welder. In my case, the contacts were not arched or pitted, so replacement at this time was not warranted. I then proceeded to use an air nozzle to blow the debris from the contactor assembly, then reinstall the cover, plug the unit's power cord back in and turn it on. My Challenger 172 was then back in business and working just as good as the first time I used it after purchasing it brand spanking new. Had the problem not been with the contactor assembly, Doug told me how to check the heat control switch and what to jump to verify that the heat control switch needed replacement. I did not go that far as that procedure was not needed. I will not repeat here what that procedure is, instead suggesting that anyone who has a problem with their 172, call Doug at Miller Tech Support and speak with him. He will then guide you through the procedure. If anyone has a problem with their "contactor" assembly in their 172, a replacement is available for about $63.00, Miller part number 108358. I plan on ordering this part in the not so distant future just to have on hand in case my contactor assembly's contact points do get pitted from use and fail. I don't like having to stop fabrication work because of welder down time and I always keep extra gas and welding supplies on hand, so it makes sense to keep a replacement part around for the most common wear out item in the welder. Hope this helps.Chris, I strongly suggest that you remove that "circuit breaker" from the printed circuit controller board and reinstall the fuse holder and the proper rated fuse that came with the welder. In the event of a short or an overload, that circuit breaker will keep resetting itself and could possibly cause damage to your welder and or start a fire. I know you didn't install that yourself, but whomever did should be reprimanded for doing something very foolish that is also very unsafe. If a properly rated fuse mounted on that control board kept on blowing, then there's a reason why that is happening and it should be addressed. Ask Miller Tech Support what could cause a fuse on the 172's controller board to keep blowing and I'm sure they will be able to help you.CJLast edited by 172madness; 11-29-2006 at 02:53 PM.
Reply:When mine stopped working I feared the worst until I found this thread. I carefully took the bowties out and lightly sanded and cleaned the contacts with brake and contact cleaner and my 172 is working like new again!Thanks for the info gentlemen!Mark

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Reply:Unless those guys are like me after 5-1/2 yrs I think they may have found a solution to the issue


Reply:Yep those guys had definitely found the solution.  My post just showed what the problem looks like. I find that posts without photos are useless.  Now at least anybody who is not Miller technician and is looking for a solution as to why their Challenger is not working can see what Miller part no. 108358 looks like. I thought it helped.  Thanks!  I think.cheers!
Reply:These were good posts.  I have a Challenger 172 also and so far so good.  It does not see heavy use.  I printed out these posts for future reference though.I don't know how many of these units were sold, but I see very few posts about any problems with them.  I hope that indicates a well built machine.Wayne
Reply:i to have a miller 172 that is not working, i will have to check the fuse and the points and go from there.
Reply:thanks for the info, took points out and cleaned them up and it is back to working again.


Reply:Here we go digging up an old thread to revive it again!I've got many of the same symptoms as above, only its intermittent. Here's a video I took. Should help I think. Bear with my meager cinematographic skillsOne observation I made was when the feeder was not working and the trigger is held down, the rheostat for the wfs started smoking.


the contacts are a little dirty, but not carbines up. I'll pull them apart to clean them

The relay seems in good shape

The feeder board had no obvious signs of burned components. Sent from my dumb smartphoneTeach Ag Mech - Mike At Home:Lincoln Electric AC225Miller Challenger 172Gas AxeWork:eclectic bunch of 90's vintage blue boxes
Reply:I love when you post a problem, then dig deeper and find out what's wrong. We'll use this for education. The contractor was fine, though I cleaned them anyway

Then I pulled apart the relay and found this

May not be able to see, but there's practically no clearance between the points and some buildup closed the gap keeping that side of the relay locked up to both poles. Surprised something didn't get really toasted, but I got lucky. Put it all back together and walah, it works again. Sent from my dumb smartphoneTeach Ag Mech - Mike At Home:Lincoln Electric AC225Miller Challenger 172Gas AxeWork:eclectic bunch of 90's vintage blue boxes
Reply:My Miller Challenger 172 has had intermittent feed problems for years.  I chased the problem swapping liners, guns, and wondering what the heck I was doing wrong.  Never fixed the problem- been acting up for about the last 5 out of the 20 years I have owned it.Yesterday that problem finally developed enough that it rendered the machine unusable.  Got on Google and found this thread.  A few minutes later I had it diagnosed down to that Midtex DPDT form "C" contact relay.  I know this thread is over a decade old, but I wanted to leave a tidbit.  On the Challenger 172 they used a double pole double throw relay (that Midtex 157-32Q200), but only used on set of the contacts (one pole).  The other set of contacts on the relay is not used for a thing!  So- I have ordered up a new relay for about $30 from McMaster-Carr 7266K47 (but it does not have the ear for the mounting screw, but hopefully better quality than the Midtex) but for the time being I just moved 3 wires over to the other set of contacts and my welder is up and running again!Thanks to the forum for existing - and if you run into the same problem with the same machine maybe swapping contacts will help you get up and running again for free.At your own risk.Obviously unplug the welder and use lock out tag out if you desire...Carefully remove the clear green Midtex brand relay and position it so you can clearly see the tiny terminal numbers in the black plastic base.Remove the "11A" wire from terminal 7 and place it on terminal 9Remove the "10A" wire from terminal 4 and place it on terminal 6Remove the "34A" and "34B" wires from terminal 1 and place them on terminal 3Leave the existing wires alone on terminals A and BMount the relay back in the original spot.See what happens...
Reply:I'm also having this wire feed issue. Bought this welder used 4 years ago and felt like I had wire feeding issues back then, but didn't know enough. Brought it out in the last few days to clean it up, feed in new wire, and get welding. I fed in new wire, and started feeding it through the gun. Midway through feeding in the new wire, the drive motor will no longer push out wire when I hit the trigger. I hear the relays and see the relays moving. Same as the last few posts. My contact points look dirty, but I have no idea how to remove the "bowties" safely. Any tips on how to take the thing apart to clean it?Last edited by yurtdweller; 01-17-2021 at 06:45 PM.
Reply:Welp, I didn't know enough to look at Fuse #1! I blew my fuse by (likely) over-tignening the stop brake for the welding wire. Bought a new slo-blo 5A fuse at Lowes and it's feeding wire again.Now to figure out why my welds look so bad! Beginner woes