Miller Gold Star 602 Welding Machine Technical Query

[Frankie]

We procured about 30 brand new 602 welding machines and we stored some of them at room temperature at about 26oC from where we pulled, tested and used for fabrication work in the tropics. Currently 20 of them are continually in use in the workshop.
However, recently we decided to bring pull from our stock of brand new 602 machines, and while testing we discovered that two new welding machines remained perpetually on alarm(fault mode)" HIGH TEMPERATURE SHUTDOWN LIGHT" on the panel while the cooling fans were not running.
We have opened and inspected for connection and everything looked good, consequently, we tested the NC thermostat on disconnected mode and it looked ok,

Again the Circuit Board has been interchanged with a functional board and the fault remained. Please has anyone experienced this fault and if yes, what was done to resolve that? Should I consider this a factory fault?. Kindly share your thoughts, experience, suggestions, contacts or proven solution(s)
or refer me to previous discussions around this.


Thank you
Frankie

[LoganpClayton]

Hello Frankie,

Logan here, I'm a certified service technician for both Lincoln and Miller, I also am fluent in thermal dynamics, themal arc, esab, hypertherm, pretty much anything from the Home Depot unit up to the Powerwave (automated) welders, I can handle. I was perusing the forums to sharpen my skills and happen to find this post.

Firstly, we need some clarification on exactly what thermal protector you tested, as this machine is looking to have 6 thermal protectors total!! (see attached picture, 4 of the T.P.'s are in the transformer itself, and the remaining two is on the rectifier bridge. I would go over each Thermal Protector, you are looking for one that is open. If all 6 show to be closed and continuous then we move on from there with a look at CR 5.

P.S. Serial numbers are key for me being able to get into the exact diagram for that Machine, to better help you, help me with supplying that serial number, thanks!

- LPC