Welder Cutting Out

[tillson]

Hello. I have just joined and this is my first post here.

A friend gave me a Clarke 100E Mk2 MIG Welder. It was a bit battered but it has cleaned up nicely and seems to function nicely.....up to a point.

I have been practicing my skills, or lack of them, on some scraps and am finding that after a very short period, the welder stops functioning and just makes a clicking noise when I pull the trigger. I have to leave the set for about 30 mins before it will function again.

I am welding 25mm mild steel box section with a wall thickness 2mm. I am using 0.6mm wire and I can probably do one run of 25mm weld and about 10mm on the other side before it cuts out. Everything is set as it should be according to the manual and the welds it does produce are acceptable.

Has anyone any ideas why it should cut out so frequently? I don't think 35mm of weld on 2mm thick mild steel is an excessive amount of work. I have cleaned the electrics with an airline so all is clean in there and nothing is likely to cause a cooling airflow blockage.

I am wondering if there is a faulty component and if so, which component it is likely to be.

Any help suggestions would be very much appreciated.

Regards

Tom

 

[rtbcomp]

Does that model have a cooling fan inside? if so, is it working?

 

[tillson]

No. The 100E doesn't have a fan. When the cutting out starts, the machine is only just getting warm. I have tried pushing cooling air through the case, but it hardly makes any difference.

 

[peterd51]

Hi,

Do the feed wheels turn when it's clicking?

I'd dismatle the torch and check that the liner is clear...mine got bunged up with dust/rust at the neck end and caused a few odd problems.

It could be a feed motor problem, one of the gear wheels stripped, etc.

Is the wire spool free to turn or catching at a specific point on each rotation?

If that all looks OK then you could try spraying components with freezer spray, one at a time, and see which one brings the set back into service, but be aware that there's high voltages inside the set.

I'd switch off each time before I sprayed anything!

The smaller Clarke sets without a fan will run for about 15 - 20 minutes before over-heating and then they'll need about 30 minutes to cool down, but your problem doesn't sound like this is the cause.

Ah, also, if you have a voltmeter, check if there's any voltage on the torch tip when it 'clicks'.

Regards
Peter

 

[tillson]

Thanks for the tips Peter, I willo certainly try some of your suggestions.

I don't think the problem lies with the wire feed. I have slackened the rollers off and the wire pulls through very smoothly and without a lot of effort. It also seems to feed quite nicely when the set is working.

When the set does trip out, the wire does continue to feed, but no arc. I have to leave it for a good 30 mins before it will strike up again. Its a bit of a pain only being able to do a 30 to 40 mm weld and then having to down tools for 30 mins.

I'll try the freezer spray suggestion although I have tried pushing a good airflow through with a compressed air line. Will also check the tip voltage as suggested.

Thanks again

Tom

 

[rtbcomp]

When it cuts out do you get the clunk of the contactor operating? It sounds like you might have an over-sensitive thermal cutout.

 

[tillson]

rtbcomp, yes, there is a clunk as though a contactor is working. Is the thermal cut out easy to check / replace? Or is it part of a bigger component?

Regards
Tom

 

[rtbcomp]

Without looking at the unit or the circuit diagram it's hard to give a definitive answer, but in general..... the thermal cutout is usually fitted to the heatsink carrying the rectifiers, there may be one on the transformer, or even embedded in it. A commom type is about 1.5cm diameter with two connections on it and fastened with a flange rivetted or screwed to the heatsink.

They won't carry much current so they are often connected in the control circuit, so I would have guessed that the contactor would not call if the cutout had operated.

 

[Wozzaaah]

Hi Tom. Normally, if the thermal overload cuts in the machine will be totally dead, no clicking, no wire feed, nada. There might also be a light on the front panel to tell you it's over temperature. Like RTB says, thermal sensors do fail, mine did, it meant the light pretty much stayed on constantly or came on after a few seconds of use. If you can find it, cut one of the wires and try running it, if it 'solves' the problem you know you have a faulty sensor which you need to replace to avoid damaging the transformer. Take a few photos of the transformer and rectifier if possible, we should be able to identify the sensor.

 

[rtbcomp]

.......If you can find it, cut one of the wires and try running it, if it 'solves' the problem you know you have a faulty sensor which you need to replace to avoid damaging the transformer. ....

Depends - most over-temperature sensors go open circuit when they trip so cutting the wire will give a permanent "over-temperature" condition.

By all means try it, if the machine doesn't work even when cold then short the device out and try again.

 

[Wozzaaah]

Sorry, yes rtb, I meant to say cut them and short the connections together, thus bypassing the sensor altogether. I'm not convinced the sensor is the cause of the problem but at least it will eliminate it.