How to Test Cooling Fan relay

[planenut]

I now have the front off my 2003 1.8 turbo, which has a habit of running the high speed fan most of the time and running on when switched off.

As I say, having removed the shroud, I am at the stage where I want to test the relays in the "control box" and ask the question, "how do I test the relays?" The resister is the original silver one, which has continuity.

[vitesse]

Have a look here: https://www.the75andztclub.co.uk/for...=294123&page=9 post 83 SD1too

Regards

[planenut]

Originally Posted by vitesse

Have a look here: https://www.the75andztclub.co.uk/for...=294123&page=9 post 83 SD1too

Regards

Many thanks for that Mike, I've put everything away now, so will try to translate this during this evening. Already observed colour differences, so will test tomorrow, thanks.

[SD1too]

Originally Posted by vitesse

Have a look here: https://www.the75andztclub.co.uk/for...=294123&page=9 post 83 SD1too

Thanks for this Mike.

Originally Posted by planenut

I now have the front off my 2003 1.8 turbo, which has a habit of running the high speed fan most of the time and running on when switched off.

Fred, if the fan runs on for more than a few seconds then it indicates mild overheating (coolant reaching 108 degrees). What was the result of the "demist test"?

Simon

[planenut]

Originally Posted by SD1too

Thanks for this Mike.

Fred, if the fan runs on for more than a few seconds then it indicates mild overheating (coolant reaching 108 degrees). What was the result of the "demist test"?

Simon

Thanks Simon. As I have the whole of the front off I am going to work backwards again, eliminating those relays while I am there.

[SD1too]

Originally Posted by planenut

... eliminating those relays while I am there.

You have already eliminated the fast speed relay since you've reported that it is turning on and off. You can test the slow speed relay by doing the 'demist test' which is why I asked about that. If you haven't already done it I recommend that you do this test now, before anything else.

The relays are very reliable. It's very rare that a forum member reports a failure but remember that if this does happen, the relay contacts stick together permanently which results in the fan running constantly. As I understand it, that isn't what you're experiencing.

Don't get hung up on the relays Fred. The first thing we need to know is whether the slow speed is working. The easiest way to check that is the 'demist test'. Just a reminder that the engine needs to be running.

Simon