Lorch HT 180 AC DC : Fault code E3

[Weldoradoo]

@eddy49 and all:
I reconnected the plug at X7 of the "Mapro" and as expected the fault E3 was back. Then I did the "Closed circuit test" with a small piece of cable between the X7 connectors. And the result of that was that the fault was gone.
Also I measured the resistance at the plug that goes into the X7 socket with 2 Multimeters: 0 Ohm in both cases.

 

[eddie49]

Those two test results, where the E3 error code is gone when the current-measuring shunt is replaced by either an open-circuit or a short-circuit implies that the POST does perform an exact measurement of the resistance of the shunt, but the program has no sanity-checks ( limit values ). The test does not expect the shunt to go OC, nor to short completely.

Attempting to check the shunt resistance with a digital meter seems to prove that they typically are not accurate for resistances below 1 Ohm.

 

[Weldoradoo]

Ok, so my Multimeters are inadequate?

"but the program has no sanity-checks ( limit values ). The test does not expect the shunt to go OC, nor to short completely."

Yeah, thats a bit strange. The "brain" of this machine should recognize OC or CC.

How should I proceed? What next step do you suggest?

 

[Weldoradoo]

I think that the Mapro is ok. And that is the most expensive part of the whole welder .

 

[Munkul]

Have you understood it correctly?
to my understanding, the machine is looking for a voltage drop across the shunt. The shunt resistance is fixed, but it will be very low. X7 will measure voltage with respect to something else on both wires, and work out the differential.
When you go open circuit or close circuit it will not see a voltage.
When powered up, what is the voltage at the shunt? It should be very low, next to nothing.

 

[Weldoradoo]

The machine "blew up" after switching to stick welding. Well a pop and some smoke. No visible damage anywhere. Will check the prints that are not directly visible for damage.

 

[Weldoradoo]

I dont dare to switch it on again until I know what happened/ whats broken after the "pop sound" and the small plume of smoke.