I've got this new to me 1979 miller airco big40. I went to use it today and had the auto idle on but it didn't kick in when I tried to weld. It wouldn't even make a spark at low idle. I ended up switching to high idle and it was fine. It was working fine last week, I changed the electric temp gage to a manual one and left the old one hooked up behind the panel just so the wires would be in place. I accidentally left the key on when I unhooked the wires and one of them sparked on something. I'm thinking this screwed up whatever makes the engine kick in to high idle. The high idle switch still works and has four wires going to it. Two of them are hooked to a spiral looking thing that tied to the ground leg going to the lead ground terminal. One is a ground and the other goes to the solinoid that makes it rev up. It's got the red seal continental engine with points. No mag.I need to know what could be wrong if anyone has any answers, thanks.Miller trailblazer301gLincoln sa200Miller251Miller spectrum 625Victor oxy-acc2002 Chevy duramax 3500 dually 4x4
Reply:At low idle you should have voltage at the weld terminals and you should get a spark.When the electrode touches work this allow current to flow. this current is picked up by the sensor and tells the welder to go to high idle. 15 seconds or so after welding is stopped. the idle control will send the engine to low idle. If switch is set in low idle and you start the welder. Does it run at high idle then go to low? The sensor detects current in the weld and on most welders the Aux power circuit. sends a signal to the idle control. There is about 6 different type of big 40 welder and a couple of different versions each of those. So can't go into detail with out a serial number and full model name.
Reply:Serial # HK232981Miller trailblazer301gLincoln sa200Miller251Miller spectrum 625Victor oxy-acc2002 Chevy duramax 3500 dually 4x4
Reply:When the switch is on low idle and I strike the rod to the work it does not make a spark. The engine does not respond. When the switch is on high idle it will weld fine. Same goes for aux power except it will barely make a grinder turn at low idle but will not idle up like it should. Works fine as long as the switch is on high idle.Miller trailblazer301gLincoln sa200Miller251Miller spectrum 625Victor oxy-acc2002 Chevy duramax 3500 dually 4x4
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I'm thinking this spiral thing is what tells the solenoid to engage. Miller trailblazer301gLincoln sa200Miller251Miller spectrum 625Victor oxy-acc2002 Chevy duramax 3500 dually 4x4
Reply: Miller trailblazer301gLincoln sa200Miller251Miller spectrum 625Victor oxy-acc2002 Chevy duramax 3500 dually 4x4
Reply:You have the older system uses a reed switch and the vacuum control in the last picture. Bottom right corner. I think you have a low idle output problem, more than a idle timer problem. Your low idle engine speed may be to low or the excitation circuit may have a problem. check rheostat and slip rings and ect. your welder at low idle has to produce enough power to activate the reed switch and cause the valve in the timer to operate. Place a strong magnet near the reed switch and see if the idle speed changes. Yes it is the tube inside the coil bolted to the output terminal.
Reply:Thanks! I did adjust the carb before I started having this trouble. Maybe it's just adjusted to low. I'll have to see. Thanks again!Miller trailblazer301gLincoln sa200Miller251Miller spectrum 625Victor oxy-acc2002 Chevy duramax 3500 dually 4x4
Reply:Well I got my dad to adjust the vacuum screw and it works perfect now. Thanks ccawgc!Miller trailblazer301gLincoln sa200Miller251Miller spectrum 625Victor oxy-acc2002 Chevy duramax 3500 dually 4x4
Reply:Thanks for this Oldie But Goodie thread! 1974 Big 40 Red Seal engine. Wouldn't auto idle up. I thought it was SURELY the reed switch. After reading THIS thread I used a magnet and found it to be good. Problem was idle speed too low and vacuum screw setting adjustment. (FYI screw facing out on intake inside of a cap turn CCW for less uptime)Back Story: Over heated a few years ago after bottom radiator hose ruptured and I couldn't get to it in time ... ( I was up on another level from it)After head work and reassembly I had inadvertently set the idle too low. Would do just fine on locked-in position but had to hold the rod down till it revved up and you had to be a VERY very V.E.R.Y. fast Arc striker to beat the idle down 🤣.So I just had been using it in locked-in position till now. Anyways , great thread reading and very informative! Cheers.
发表于 2021-12-31 15:51:19