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Miller Dialarc Power Issue

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  • Miller Dialarc Power Issue

    Miller Dialarc HF w/ Power Factor. Ser. # JG097521 which I bought new in about 1986 / 87........Primary use TIG , Water cooled with a Bernard cooler and WP-20 torch. Built many Race Cars with it and just started another Project after it being Idle for about 3-4 years other than just a few minutes here or there.

    My eyes have suffered some since the last build and was having some issues seeing the puddle and then installed a 2.0 power cheater in the hat which helped allot...........Been practice welding mild steel CR 1/4" plate to .125" plate using 3/32" tungsten and 1/16 or 3/32" filler rod and not doing to bad but continued to think perhaps the machine was low on output in the middle heat position which is 40-190 even with the fine adjustment Amperage rheostat set a 90-100. As I continued to work on the basics like Argon flow ( 15-20 cf) and different filler materials er70s2 and s6 and 309 stainless getting comfortable under the hood again I continued to feel as though I needed way to much pedal or near 190 Amps to create a puddle just to get started , but then of course once welding it was hard to manage even after I throttled back some as at that setting it would tend to undercut the 1/8" material and the welds just looked washed out with to much heat..........I tried speeding up some but that didn't work either. My feeling was I should only need perhaps 125-140 amps for 1/4 to 1/8" material. I talked with a couple of guys st the store who pointed me towards the RFC-23a foot Pedal which I took apart & cleaned the square 4" tall resistor face some with a stainless brush added a little pressure to the brush assembly and even went back in and reversed the resistor end to end while also changing the white & black wire accommodate that..........which all seemed to help......

    Today just when things were looking real good I went back out in the shop just to practice some more and while set in the 40-190 position with the rheostat set at about 70 and the pedal buried , it would not even create a puddle........I increased the rheostat to 100 but still no Joy! Had a weak arc that would not melt the metal. I Switched the lever to High range 125-310 and set the rheostat to 30 and it welded fine , great puddle and great looking welds more like I'm used to. I never really tried the low 40 amp range other than it did have a small arc.

    So is there a High / Low Transformer or coil that's out? Is there some more testing I should do to better figure out whats wrong? Could it be the contacts on the levers that went Bye Bye? .................................What say you?


  • #2
    I've never seen an Idealarc inside, but from your description and looking at the diagram (thanks for the serial number!), I would first suspect the contacts on the range switch. In general, switch contacts are FAR more likely to fail than a transformer winding (my long ago time in life as a reliability engineer is showing). Transformers do fail, but it is certainly not a very common occurrence compared to other things, especially moving parts. If it's just corrosion from sitting so long, you may solve the problem by simply moving the range switch through is positions a couple of dozen times. Do not move it while welding.

    Much Less likely, since it welds on the higher setting, but it could also be bad contacts on the weld contactor labeled "W". You can see its location on page 1 of the parts list in the manual

    Wouldn't hurt to clean those contacts anyway after the machine sat so long.
    Last edited by Aeronca41; 08-04-2016, 05:42 AM. Reason: Added info about contactor.


    • #3
      Change the contactor


      • #4
        Originally posted by cruizer View Post
        Change the contactor
        There's the word from the guy who knows. Just do it. He knows his stuff.


        • #5
          Thanks Aero & to add to the mystery yesterday afternoon I disconnected the Power and pulled the sheet metal covers.......The copper blades looked good , they did have some old green grease on them which I assume was factory...........I cleaned them with a rag first and then wire brushed , checked all the terminals going to that block with an Ohm meter on all positions and while there also pulled the single copper blade tap going to the mid-range 40-190........short of the normal witness marks on the copper from sliding back and forth over each other for 30 years there was no grooves or corrosion to speak of................coming from that same tap there is a short cable that connects to two large copper wires that come out of the winding's on the transformers.....the three were clamped together......looking around and inside the clamp there was some indication of dis-coloring and corrosion. I cut the metal clamp off and then proceeded to clean the two large wires and also wrapped the stranded end of the cable tighter and soldered so it would remain firm........then took a standard electrical Copper ground clamp and clamped together all three leads................turned the machine back on and the Middle range was still DOA...........with just a small arch I assume coming from the HF and then switched it to the High side which the day before was working and now the high side was on a death spiral down to a much lower power. Tried different ranges in the large amperage Rheostat but no difference.................

          So when you say change the Contactor are you taking about the 3 copper blades as I mentioned above? and / or the Contact assembly # 032-786 which is one in the same?? I did use some di-electric grease on them when I re-assembled...........but ran the leads from the OHM meter across the connections...........There is also two parts to that that moves with the switch handle and the other that is stationary on a bracket.......

          so what say you?


          • #6
            Sounds like good steps so far, even if it went downhill after. I'm confused by "the 3 copper blades as I mentioned above? and / or the Contact assembly # 032-786 which is one in the same??". From earlier in the post I thought you were referring to the polarity switch when you talked about copper blades. The contactor assy 032786 is the "W" weld contactor and is not part of the polarity switch. I may be misinterpreting what you are saying there. That 032786 is the contactor Cruizer thinks is bad. Have you tested wth the STD/REMOTE switch in STD to take remote right out of the circuit?If you flip that switch back and forth can you hear and see the contactor energize and de energize? Does it look and sound the same in remote when you hit the pedal?


            • #7
              Areo...........Sorry about the confusion , Yes I was confused by the term Contactor and in my mind I was thinking and seeing the bladed copper Contacts as an issue? loose pages in my manual were not in order so I now see what you folks are talking about............a switch / Contactor "W" 60 Amp 3 pole 600 volts #032786 ...........never looked , seen or checked that..........I believe that is down in the bottom of the the coil #035-837 mentioned on the line below that in the parts list part of the Contactor? Do they come as an assembly and need to both be replaced?

              So my question is now this: In the first instance the 40-190 tap failed first , but in the next moment I switched to the 125-310 tap and it welded fine...........then the next day the 125-310 tap also went downhill............if the Contactor was at fault why did it weld OK on the High tap but not the Mid tap and why did it later fail?......................I would have thought that if the Contactor failed would it not have just failed across the board on all Ranges at the same time?

              I am away from the shop today so cannot check the remote........when I last tried on Wednesday on the High tap it would strike and arc but had very little power to make a puddle.

              I appreciate all the help..........Thanks Again


              • #8
                And while were on the subject of Dialarc welders of which mine is the Power factor version.............I have heard that there is some benefit in having this either dis-connected or re-wired..........not sure how to do that.

                What is your opinion on that?


                • #9
                  Merely disconnect the power factor caps, unless your using the machine 12 hours a day, the PF's are useless. As for why your machine worked for a short time, the contactor points are worn, then over heat adding to loss of power in 1 or more of the legs, 99% of the time its a failed contactor in the Dialarcs, ie, why I mentioned it. Not a big deal, though, Its a rather inexpensive fix anyways, so why not replace it.
                  Last edited by cruizer; 08-05-2016, 04:09 PM.


                  • #10
                    Thanks where do I find the Contactor , I have been looking on line without much success.......using the part number mentioned above. And is the Contactor connected to the coil as an assembly or do I replace them both?



                    • #11
                      Originally posted by tarry99 View Post
                      Thanks where do I find the Contactor , I have been looking on line without much success.......using the part number mentioned above. And is the Contactor connected to the coil as an assembly or do I replace them both?

                      Have you tried these guys...??


                      The more you know, The better you know, How little you know

                      “The bitterness of poor quality remains long after the sweetness of low price is forgotten”

                      Buy the best tools you can afford.. Learn to use them to the best of your ability.. and take care of them...

                      My Blue Stuff:
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                      TONS of Non-Blue Equip, plus CNC Mill, Lathes & a Plasmacam w/ PowerMax-1000


                      • #12
                        H80N , Yes and they did not have it listed..........although I just found out the part number has been up-dated so I need to go back and look again.........has anyone bought any parts from this company in Texas called Weld Mart on Line? they seem to have the hottest prices on these parts.


                        • #13
                          If you can get the Miller version, that would be better as it has the space for the 2 brass lugs, however you can always modify the cable type by shaving and bending the brass lugs All your after is a 60 amp 120Vac definate purpose 3 pole contactor Goes up to a #252907, pretty pricy for a contactor, that I can get jobber for under $40 I generally use "TopLine".

                          There is a GE 60amp definite purpose 3 pole with 120 vac coil on that will suit you nicely.
                          Last edited by cruizer; 08-05-2016, 04:23 PM.


                          • #14
                            Thanks Again Cruizer and others...........when I get the parts I'll report back in.


                            • #15
                              Just to follow up on my Problem with my Dialarc 250 HF ............Cruzier was correct the Contactor was in fact defective........I did although remove the original Contactor from the machine and removed the 6 point contacts that engage and distribute the power within........most showed some pitting and also some blackness from not making very good contact...........while waiting to buy a new one I took a stone and dressed up the 6 individual points and reassembled the Contactor and re-installed it..........Walla Worked I'm not suggesting this as a fix all or that anyone should try this. I merely did this as a method to trouble shoot the need? ..............Finding a replacement Contactor is perhaps not that easy as the old Contactor is quite large vs the replacements are quite a bit smaller...........As Cruizer mentioned the part is pretty basic and used in allot of applications beyond welders........and can vary in price from $40 bucks to $300. I did find one that I liked and was able to use the existing mount by just adding a few new holes.......the copper bus bar had to be replaced with a smaller version........but all and all the old machine now works fine again.

                              I would like to Thank all of you here that helped in the process........the group of folks here is truly outstanding!

                              To follow up...........I've had the Dialarc since new and it still looks new..........But, I never quite liked the sine wave for welding aluminum and decided to invest in a new Miller Dynasty 280 DX which I am now enjoying all the new tricks that it can do................My son-in-law is buying my old welder so life moves on..........glad it's still in the family!