Speed controlled cooling fans

Kitch · Post by **Kitch** » Sun Feb 20, 2011 1:09 am

Clever one,this. My cooling fans cut in when I start going fast(ish)! My coolant level is fine, it\'s not overheating and to my knowledge they cut in when they should. But if I start doing 80mph - 100mph, I can hear them cutting in occasionally, but only when I\'m travelling at that sort of speed

I did try going upto about 125mph to see if they stopped or got worse, but my ears couldn\'t take the battering!

Really weird. It\'s a standard fan with a relay controlled second fan setup. Can\'t tell if it\'s both of them cutting in or just one or the other (but the second one can\'t work without the first obviously).

Maybe the wind blows the wires to the switch and shorts them out?

Way2go · Post by **Way2go** » Sun Feb 20, 2011 1:43 am

Higher flow of hot water heating down to the temperature switch where at lower speeds there would have been more cooling through the Rad? Could also be exacerbated by partial blockages in the Rad?

(Try a Rad Flush with Barrs Professional Flush, that clears the passages!

)

Kitch · Post by **Kitch** » Sun Feb 20, 2011 1:51 pm

It\'s a new rad though and the coolant isn\'t gunky, it\'s clean as a whistle! Unless it\'s popped it\'s head gasket or the seal in the heat exhcnagers gone and it\'s accumulating shit down by the sensor? Shouldn\'t be, I only put the engine back together 2 years ago!

sdelasal · Post by **sdelasal** » Sun Feb 20, 2011 5:49 pm

are you sure you're sure that it is the fans coming on? At that speed the engine will be making a hell of a racket and you've got wind noise and road noise too. Disconnecting them electrically would remove any doubt. Steve

electrokid · Post by **electrokid** » Sun Feb 20, 2011 11:14 pm

I did try going upto about 125mph to see if they stopped or got worse,

I was just checking the cooling fans Officer

Why not hook up a couple of LEDs on the dash to tell you when the fans are powered ?

Kitch · Post by **Kitch** » Mon Feb 21, 2011 8:30 pm

Yeah definately sure they\'re coming on. The original N/S fan (the two speed one) is quiet, but I\'ve hooked up a relay which is triggered by the original fan coming on and kicks the second one into life about half a second after the first one. Thing is I used a fairly heavy duty relay and fairly heavy duty wiring, so to say it spins quickly is a bit of an understatement - it\'s bastard loud. In fact I swear if it comes on at the lights I start moving backwards!
I\'ve found at around 60mph it doesn\'t come on, but sitting at a prolonged 70-80mph, it does. Winding it past three figure speeds doesn\'t change a thing, which makes me think it must be wind related

Way2go · Post by **Way2go** » Mon Feb 21, 2011 9:13 pm

Kitch wrote: I've found at around 60mph it doesn't come on, but sitting at a prolonged 70-80mph, it does. Winding it past three figure speeds doesn't change a thing, which makes me think it must be wind related

Have you tried disconnecting the fans and taking it for a spin down the motorway? After all if you keep moving then you shouldn't need the fans. If you then hear the noise then it could indeed be wind causing them to turn as the BX fans don't "feather" when they're off, do they?
Also if you see your temperature gauge rising above normal after 60mph then you'll also know there is an efficiency problem with the radiator for whatever reason.

Kitch · Post by **Kitch** » Mon Feb 21, 2011 10:49 pm

Sorry I didn\'t make it clear enough; I don\'t think the noise is the wind spinning my fans. I think the wind might be pushing some wires together (or something equally as straw clutching) and shorting them out. And that really is a long shot!

Haven\'t so much as opened the bonnet yet, I just keep driving it! The coolant temp gauge never reads above 80 degrees unless I hit traffic and the coolant level warning lamp does work. I might just put it down to a character quirk of the car until something fails terminally (and I blame the car/smash it up/burn it/etc), and then I\'ll be able to see what it was

electrokid · Post by **electrokid** » Tue Feb 22, 2011 8:14 pm

In fact I swear if it comes on at the lights I start moving backwards!

If the fan is pushing air out at the front then that's your problem

Post by **Defender110** » Tue Feb 22, 2011 9:22 pm

Yes blowing instead of sucking just doesn't do it

Kitch · Post by **Kitch** » Tue Feb 22, 2011 11:49 pm

electrokid wrote:
In fact I swear if it comes on at the lights I start moving backwards!
If the fan is pushing air out at the front then that\'s your problem

Yes I wasn\'t being completely serious there!