Highlander Posted November 19, 2002 Share Posted November 19, 2002 Having nearly completed my first 7 build it was started for the first time on Saturday. Hurrah! Having run it for some time to check the radiator fan cut in at the right temperature, it was stopped and left withthe ignition on to check that the fan cut out again. Which it did. Ran the car again that afternoon to do something else and the rad fan failed to cut in. Some quick investigation showed that the fuse hade blown (15A). Replaced this and all was well Fan cut in, cut out as temp dropped. On third run fan again failed to cut in, again having blown the fuse. Anyone come across this before? Got any suggestions? Suspect that it could be a problem with the sender. Link to comment Share on other sites More sharing options...
Miraz Posted November 19, 2002 Share Posted November 19, 2002 Check the wiring run for the fan and the thermo switch - it's very easy for the jubilee clips on the radiator hose to rub through the insulation and create a short circuit. Link to comment Share on other sites More sharing options...
Graham Sewell Posted November 19, 2002 Share Posted November 19, 2002 I would say that 15A is marginal for the cooling fan as it draws 10A when stable and quite a bit more for the first few seconds as it spins up to speed. So unless you have got a fuse that can withstand a short surge, it will blow. Try raising it to 20A. In case you are wondering, I measured the current used by the fan a few years ago when I was putting together a manual override switch and needed to spec the wiring. Low tech luddite - xflow and proud! Link to comment Share on other sites More sharing options...
Highlander Posted November 19, 2002 Author Share Posted November 19, 2002 Miraz, The wiring appears OK, (brand new, never been run), and a short to earth would run the fan all the time as this is effectively what the thermo switch does. Graham, I must admit that I though the 15A was perhaps to small. Could be that it has the wrong fuse, but didn't want to start throwing larger fuses at the problem until I had confirmed this. I might try it again at the weekend with a 15 and see if the 'switch off' by the thermo switch is causing a current spike large enough to blow the fuse. Cheers guys Link to comment Share on other sites More sharing options...
Highlander Posted November 20, 2002 Author Share Posted November 20, 2002 Checked the fuse size in another workign car and the 15A fuse is the correct one. Any other ideas anyone? Link to comment Share on other sites More sharing options...
Seven in SA Posted November 20, 2002 Share Posted November 20, 2002 Highlander, Does the fuse blow as soon as the fan switches off or did you switch off the ingnition after it cut out. It might be worth running it and then keeping the ignition on until it swtiches off. At that point check the fuse, if its gone re-check the wiring. If it's ok, turn the ingition off and then back on again, check the fuse. I had a windscreen wiper fuse that kept blowing, went through something similar to the above and discovered that it was something else causing the problem. I can't remeber exactly what it was but the other wire was contacting under the dash and fusing the wipers. It should help you narrow the problem down at least. Nic Link to comment Share on other sites More sharing options...
Highlander Posted November 25, 2002 Author Share Posted November 25, 2002 Problem solved. It was the sender in the radiator that was duff as I suspected. Caterham replaced it and it now works fine. Link to comment Share on other sites More sharing options...
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