Breezy_Pete

You should have this:

Can you post a photo of your engine bay? There is a rubber seal that goes along the top of the 'water box' (the section below the windscreen wipers), and all the way around the engine bay, to seal against the underside of the bonnet. This should keep any leaked exhaust gases from entering the ventilation system inlet (which is inside the water box). This is quite a dangerous situation. If the leak is upstream of the catalytic converter (like at the head/manifold junction) you could be breathing carbon monoxide (CO) which can make you fall asleep and die.

Any of #57 - #66 inclusive, where there is a fuse fitted.

Browse here to find the part numbers of what you require. https://www.lllparts.co.uk/catalogs/skoda/CZ/FAB/697/8 May be able to order from them too.

Hello Michael, thanks for getting in touch. I'll be glad to help with this, and will send you a Private Message in a minute. 👍

Is anti Islamophobia really a thing?

It is a CUNA engine, car was built 24/02/16. Part number of after-cat sensor is 04L 906 262. Is that what was fitted as the replacement? Or aftermarket equivalent? Your oxygen sensor wiring is as shown here G130/Z29 seems like the one you need to focus on. The red wires are both fed by fuse 8 in the engine bay fusebox (10 Amp). The black/white wire going off the top of page will not be relevant.

Within erWin, when logged in:- Go to Individual vehicle info tab, select repair info, then model, then circuit diagrams. There may be more than one huge pdf of circuit diagrams depending on year. When you have paid your 'flat rate' they will have download buttons. Save somewhere safe, then, use ctrl-F within them to find specific functions. Or the index/menu drop down on the left.

Secondhand genuine from ebay. Photo of perceived problem?

Measure either side of the fuse that connects alternator to battery. First one of the strip fuses above battery, usually.

Fling your VIN my way and I can tell you which rad part number you have.

Hope the mating connector in the loom is OK?

@mczakk PM incoming in a minute.

I'm seeing signs of availability (on partslink24) on kits suited to Roomies built on or after 28/05/2012, is the one you're looking at a 12-reg or 62? If the latter there's a decent chance it was built after that date. Sorry, but cross-checking those part numbers against what's on offer at LLL parts suggests they're gone too. ☹️ Have you @Rheumy got an image of the connector involved? May well be able to still buy that?

Hmm, how many connectors, pins, wires...?

It will have the combined unit; I think March 2010 saw the last of the separate central convenience control units in Roomsters. @Tech1e almost certainly knows the answers to your other queries. If you message me the VIN I could look up which BCM part number it has, if that's any help.

Need to know engine code as well if you would like me to try to look up wiring info. A quick glance at a guessed CUNA engine circuit suggests there are two oxygen sensors, which surprised me, and possibly the garage that may have replaced the wrong one?

@mczakk were you able to navigate the parts catalogue link I supplied?

Follow the hard plastic pipe from the brake servo (behind brake fluid tank) towards the engine. At each point where it connects to the one-way valve, look and feel with finger tips all around it for cracks. If there is another connection of hard pipe nearer the engine, check there also.

Manual or automatic gearbox?

Can be because of a brake servo vacuum hose that has developed cracks and is leaking air. Which engine size does your car have?

https://www.lllparts.co.uk/catalogs/skoda/CZ/OCT

Some of these things that look like just relays contain circuit boards which make them 'control units' rather than just simple relays. Usually the outer cover can be unclipped to reveal these extra components.

No need, the number you suggested is correct.

1J0919506M is your fan controller part number, I'm pretty sure. Has two relays inside, one powered by that fuse 8, the other by one of the strip fuses. It hangs off a bracket on the nearside chassis leg, quite near to the thermoswitch. Stuck relay will be the problem, another module swapped in should fix it.