Welcome to the forum day101
I can't believe it hasn't got a control on the front panel but if not then it must auto adjust the speed as you adjust the voltage. There may be a pot on the PCB you can adjust
What machine is it and can you post a pic of the front of it just for reference?
Oh dear that's not a good thing. I'm going to have to stop defending SIP if they are going to come up with this sort of thing.
For the wire speed, many welders automatically adjust wire speed with power setting. But all have knobs for the wire speed as it does need to be adjusted for different welding positions.
Can you send it back as not fit for purpose? Or broken?
I can't think of much good advice. If it were me I'd try them for a refund on the basis it doesn't work right. You'll have lost £15 quid petrol and the time. But SIP-Direct will most likely have you come over, decide it does work and send you home. Though they might be honerable. Try the things in my first post above first.
For my part the buyers guide is overdue for an update to try and cover this sort of thing.
Hopefully someone else on here will have some better ideas.
I'm really sorry day101 but I reckon you've got a £100 lump of uselessness .
You only have two settings, 40A and 80A so you're really limited as to what you can do with it.
My advice is to get rid of it. Sorry if that sounds a bit blunt but even if you get the wire speed running reasonably it'll still not be much good for car stuff at 40A minimum, you'll blow holes left, right and centre
I would definitely try the "not fit for purpose" angle, and write the petrol off to experience. Get the vendor to show you it working properly. If he doesn't want to or can't, threaten him with action under the sale of goods act and point out that he could be liable for Court costs and your out-of-pocket expenses, such as a professional opinion.
Did you say you wanted it for car panels? and if so did he say it would be suitable?
Ebay would take a dim view if you bought it privately having seen it advertised on ebay.
Dunno RTB, I doubt a vendor would give a refund, maybe a replacement machine would be the best he could hope for. I'm getting deja-vu here, we had a similar thing a few months back where a member bought a silverline mig which was next to useless too .
It also depend on how big your balls are to put it crudely, if you have the right demeanor and you're armed with the right info then you stand a good chance of a result .