Mainly curiousity driven question. How long is it normal for the radiator cooling fan to stay on during a cooling cycle ? I have noticed that if the ambient temperature is 10C or more and I am crawling in traffic or waiting at lights or something that the fan will come on for about five seconds then go off for about 15 seconds and so on. If the outside temperature is colder, it barely ever comes on but if it does the same sort of pattern is followed. Clearly this is not doing any major harm as it has done it for the last 100k as far as I remember and it does not lose coolant or anything. Of course I can't be sure due to road / engine noise, but I don't think it does it on the move due to the cooling effect of outside air through the radiator. Must cause quite a significant voltage drop though, as can be seen if the car is facing the garage door at night with headlights on. The fan causes the lights to momentarily dim a bit as it kicks in.
Is this normal or should I get something checked ?
Edited by Pugugly {P} on 20/01/2008 at 16:05
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The fan relay on those is a totally ECU-controlled actuator and that's perfectly normal. The ECU will be programmed with exact parameters for fan operation under almost every conceivable condition. [The ECU doesn't just know how hot the engine is - it also knows how hot the weather is and, possibly, even if the sun is shining.]
The 5 seconds on - 15 seconds off sequence sounds like a 25% duty cycle command. It'll probably use stepped 50%, 75% and full-on duty cycles as the need arises.
Crude temp switches had to wait until the engine had cooled sufficiently before switching off; the ECU is anticipating the requirement and using a precautionary approach.
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Thanks Screwloose, I never knew my car was so clever !
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i heard that temp sencing on those is very accurate.
is your aircon on when you notice this, as my fan is never on, only when the aircon is on
so long as temp gauge is ok. mine is never past the half way mark
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Hi indymorg, Yes, I always leave the climate on and like yours the temp gauge never moves from "normal". I'll try it with the climate off for the curiousity value.
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most likley the air con making the fan cycle in that pattern. If the gas charge is a little too high tha fan will cycle a lot more.
Doc
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Thanks IJ. In your opinion then, if my test of switching the climate off works, should I have the gas charge corrected or does it not really matter ?
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Hi Shoespy, sounds normal though regular cycling can indicate an issue, have a look at the following thread:
www.honestjohn.co.uk/forum/post/index.htm?t=43009&...f
Aprilia, elekie doc and DaveN were particularly helpful, I learnt a lot about how it worked.
In short I replaced fan resistor in the rad shield, had a repeat of the same issue a year later and replaced it gain with a revised part.
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Hi Cheddar - Thanks for that ( sore brain now ! ) Thank goodness it has a sunroof as well, being the no-cost option, I might just use that instead ! ( Scottish sense of value prevails again ! )
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I wouldn't worry but worth a check of the conrol pack to make sure fan is running on slowest control. Don't panick with air-con, if fan control ok worth getting gas pressure checked to make sure its not going to high to quickly, if it is then could be to full of gas. Condensor may be worth a wash through with traffic fiml remover ,if clogged that can be yet another cause of cyling fan
Doc
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Thanks I/Doc ! - Sorry for late reply. Tried a couple of days with AC off and as predicted the cycling stopped. Thanks again to all for very useful advice.
SS
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