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Rad Fan On Constant
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Old 01 Apr 2008, 07:00 PM   #1 (permalink)
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Join Date: Apr 2008
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Rad Fan On Constant

hi there new to the site so hopfully someone can help!!

my problem is soon as i turn the ign key the fan starts. ive replaced the switch, checked all fuses and wires etc but still no joy.
does anyone have any idea to what the problem can be!!
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Old 01 Apr 2008, 08:01 PM   #2 (permalink)
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The fan shouldnt come on till the high 80's mid 90's. My guess would be the fan relay is stuck closed or its been bypassed so the engine runs cooler. Its a high power relay so should be in the engine compartment box by all rights.

I use a power fc instead of the original ecu and it brings the first fan on at 91 C.
Im sure someone will come along and give you a definite answer though on where this relay is etc.
Liver is evil!!!!
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Old 08 Apr 2008, 06:22 PM   #3 (permalink)
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Try This


I had the same problem last year on my old car (Toyota Celica), same as you I tested all the switches, wiring etc and all were ok.

Try this - after running the engine for a while for it to warm up check the rad inlet and the outlet hoses (careful they and the rad may be hot, and I would advise turning the engine off before sticking your hands in there). What you are looking for is one being much cooler than the other.

What I found was that the water wasn't circulating, thus hot water was staying near the temperature sensor in the rad, making the ecu think that the engine was hot and needed cooling, hence running the fans continually.

This could be the result of a faulty water pump or thermostat - in my case changing the thermostat fixed the problem - nice easy and cheap fix.

Dont know but guess the same principles apply for the Impreza, if you are unsure about any of this ask at a garage (they should be able to check the thermostat quite inexpensively).

Hope this helps,

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