Airco 300 Heliwelder IV Continuous Post Flow

[Sprint9n]

I have an Airco Heliwelder IV, 300 AMP; serial #MG912011 that is exhibiting continuous post flow regardless of the post flow or other panel settings. I have tested with and without the remote, no change. After review of the troubleshooting guide in the owner’s manual, I replaced the post flow potentiometer (w/ Honeywell Clarostat RV4NAYSD105A) which did not cure the issue. It appears the potentiometer may have been changed previously and I’m suspect of the timer as well ((#CLF-41-30060) 24v). I can't see any movement of the contact - they to stay in the middle position. Can anyone provide insight into curing this problem? I can provide further details related to the current installed components as well as photos.

[bvd1940]

I have been hunting for a manual on the 300 Heliwelder and was wondering if there is a possibility of getting a copy of yours???
You can email me at [email protected] if you are so inclined.
Thanks in advance.
Bill

[Aeronca41]

Best thing would be if you could post a readable copy if the schematic from your book.

Miller made a lot of the Airco welders, but not all. Couldn't find anything under those numbers on their site. Might be Esab?

[Burnt hands]

Here is schematic of my Heliwelder IV - 1341-0176

[Aeronca41]

Unfortunately with the (lack of) ability to post photos to this forum with any degree of success, it is unreadable when enlarged above postage stamp size. Thanks for the attempt.

[fcanaan]

Have you tested the solenoid that controls the gas flow? Its quite possible that its stuck open. Try to determine the solenoid valve coil voltage, apply it and see if anything happens.

[Burnt hands]

Resized photo of schemetic - hope it is useable. -

[fcanaan]

Are you getting preflow? Do you have preflow on? Is the torch outputting gas as soon as you turn on the bottle or only after you stomp the pedal?

[Aeronca41]

Are you getting preflow? Do you have preflow on? Is the torch outputting gas as soon as you turn on the bottle or only after you stomp the pedal?

Good question. Please provide more detail of exactly what happens fron power on through attempts to weld. Was able to print out a readable copy of the schematic.