Overheating when air con is on

Pedal vibration, overheating/heat through the vents with aircon on, this caused my radiator fans to blow the fuse.

The vibration were the fans trying to kick in I think.

I presume you've checked the coolant level? It could still be a fan fuse problem as there may be intermittent cutting in and out if the fan fuse is corroded. This thread is worth a read if you haven't already, as it's a very common problem: http://www.seatcupra.net/forums/showthread.php?t=89756&highlight=fan+fuse&page=5

It does still seem suggestive of a fan/rad problem as it's when at idle without cool air running through just by the cars speed that the fans are likely to be more in demand. Either that or water pump. Regarding the fans, just check to see from cold with the climate control off that the fans aren't running then switch the climate on and the fan should run at slow speed to cool the compressor. When fully warm and when required the fans should go up to full speed to cool the main rad.

bigfella_V5 said:

SO, just to clarify the secondary fan should be running slowly when the aircon/climate is on?

Click to expand...

Correct. After I got my fan fuse re-routed I tested it as advised and yes even from cold when you switch on the air con the fan should turn at slow speed.

Well I just got it done locally because I didn't want to drive anywhere with it overheating, but I would try just changing the fuse first if the fuse board itself looks OK. The garage I used insisted on charging for diagnostic work regardless of the problem so I wouldn't particularly recommend them, although what they did with re-routing the fuse seemed fine, but thats because my fuse board was damaged. That said there is speculation that there is an underlying issue and a solution was posted on the UM-MKIVS forum somewhere. I will try and find a link.

This link's worth a read, but I've not done the mod they suggest. http://uk-mkivs.net/forums/thread/449470.aspx

If my fuse goes again I will look into it. Some of those in the Ibiza section have had their fan fuse go several times, although it seems Golf V5's (and therefore Toledo's) are also vulnerable.

Sorry to ramble on, but I've just found a thread I posted a reply to where I showed pics of my re-routed fuse. They are very small photo's and a bit unclear as it was a quick jobbie taken on my mobile. http://www.seatcupra.net/forums/showthread.php?t=113364

My climate started playing up a bit but this was because the fans weren't working. Resolved with the new fan fuse. Start off with the smaller things (fuse) and work bigger. There however my knowledge ends. I wouldn't know how to do my own electrical testing. Are your fans working at all? If not change the fuse then if that fails have a good look at the fuse box and test that first. That said, the info on the MKIV forum does leave me with a niggling concern - but then I've not had the issue with the fans 'pulsing' - they just stopped working completely. I will just monitor for now. I periodically check the slow speed fan works with the climate on and I know the main speed fan kicks in because I do a fair bit of driving in stop start traffic and in this weather the fan has to do its job.

Don't want to tempt fate. But you could take it for a spirited run to get it nice and warm then park up somewhere sunny and sit on the revs a bit. Either the fan should kick in or your temp will start to rise. You may just never have been in a situation where the cooling effect of air over the rad was not enough on its own - especially as you haven't had the car all that long. It was not until I was seriously held up in stop/start traffic after a motorway run that my engine temp rose, yet I had been thinking the climate control hadn't been working properly for a while. Chances are it's that that you notice first until your engine seriously overheats - which mine did to quite a big extent (didn't notice until the lights and beeps told me something was wrong and I saw the needle rapidly approaching the top of the range). I was lucky it did not appear to have damaged other components, although my idle actuator had to be reset.

For the purposes of the test ou could try with it on, but as I say the fan should turn slowly with it on anyway otherwise the compressor is not being cooled and that could lead to big bucks eventually. If the temp starts to go above 90 and there's no signs of the fan on speed stop the test straight away because it should certainly have cut in by then. My coolant was bubbling away nicely by the time my bells and buzzers went.

Until you get the problem sorted I would consider not using the aircon at all, annoying as that may be in this hot weather.