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25th March 2020, 15:27 | #1 |
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How to Test Cooling Fan relay
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. |
25th March 2020, 16:08 | #2 |
I really should get out more.......
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25th March 2020, 16:24 | #3 | |
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25th March 2020, 17:25 | #4 | ||
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Quote:
Quote:
Simon
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25th March 2020, 18:00 | #5 |
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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.
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26th March 2020, 07:27 | #6 |
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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
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26th March 2020, 09:05 | #7 | |
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I am back to the car in ten minutes and will again assess your advice, thank you. Thankfully just found the wiring diagram in Haynes, though the picture reference earlier has different colour wires. Last edited by planenut; 26th March 2020 at 09:08.. |
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26th March 2020, 09:49 | #8 |
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Hi Fred.
In addition to what Simon is saying have a look at the thread below, also change the silver resistor as par for coarse to a gold one. https://www.the75andztclub.co.uk/for...ead.php?t=1371
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27th March 2020, 07:06 | #9 | |
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Regarding testing the slow speed relay, as you say that your silver resistor has continuity, running the demist test will prove that. It really is the easiest and safest way to check the relays but you can, if you prefer, remove them for testing on the bench using a 12v supply and your multimeter across the contacts. Simon
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27th March 2020, 07:15 | #10 |
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Well as I am on "call out" for work, I have put the whole thing back together, and not wanting to sound big headed, but a lot of you will understand, I put it all back without resorting to the manual and with no bolts left over. Once you've done that it does make you realize that though there is a lot involved, it can be done. So, if I get called in, I can test the car.
As to the testing of relays, well it produced no result that I understood, and yes, I had looked at the need for replacing that resistor but could not see how one would extract it and connect it's replacement. I will research that when I'm stuck in work, on my own. Whilst all dismantled, I had another look at my non-working n/s sidelight, establishing that the "break" must be somewhere between the switch and the multi-plug, in the loom I suspect. So, it's well hidden and not sorted but may just have to run a wire from somewhere, at another time. Thanks to all for your suggestions and advice, it is appreciated, but it does require someone at this end with a bit more ability maybe. At least I know now where the go when I have done some more reading of the advice. With the current situation regarding the virus, and the fact that all of my pre-arranged events up until September have been cancelled, I will have some time to get back into it. Last edited by planenut; 27th March 2020 at 07:18.. |
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