cooling fans - not cutting in

shaunthesheep · Unread post by **shaunthesheep** » 03 Jul 2003, 23:15

all, noticed today that my cooling fan is not cutting in at the correct temp, normally cuts in about 90
water level is fine, fuses are fine, temp gauge in car seems to be ging up/down.
did have a front end crunch with someone this week, but did'nt do any damaged to my car, but now i'm beinging to think otherwise.
could the above accdent be the result of the fans not working?
any replys would be good, will be taking off the bumper this weekend to have a good look.
dom
p.s. have also noticed that one of the pipes has broken off the charcoal canister in the engine bay, might this also contrubte to the problem?

sooty · Unread post by **sooty** » 03 Jul 2003, 23:51

The fans are normally controlled by a sensor in the radiator on one of its sides. Best check if you have dislodged the connection to the sensor when you had the bump or any damage to the wiring.
If everything is in place, you can do a simple test to check whether its the wiring or sensor failure.
Get a short piece of reasonable size cable approx 50/75mm long with the ends stripped back by approx. 5mm, then remove the connection plug from the sensor and push the ends of the wires in the two spade type connectors making a loop. Being sure they are not touching each other, switch the ignition on and if the fans start your wiring is OK, but a dud/faulty sensor is why your fans don't run as they should do.
Sooty

shaunthesheep · Unread post by **shaunthesheep** » 06 Jul 2003, 06:14

well guess what, tonight whilst still in traffic, the fan cut in!!!!!![:0][:0] so it's still working, but will remove bumper on sunday just to confirm that nothing has got broken/dislodged etc.
dom

Unread post by **alan s** » 06 Jul 2003, 07:50

Just purge that air in your cooling system; I have seen a bit of air in there causing this syndrome on occasions.
What can happen is that an air lock forms in the region of the sensor switch. These switches will only work on contact with the actual hot fluid but seem reluctant to trigger in hot air, hence they don't trigger.
The air lock moves & allows the coolant through & you think all is well until one day right out of the blue, you smell something hot & when you stop at the next set of lights you see steam coming out from under the bonnet. An inspection shows water spurting out of some very inflated hoses due to the steam pressure in the system. A good thorough bleeding & the problem is solved, even though the local grease monkey has probably already booked the car in for a new head gasket & told you that the head may even be cracked, 'coz he's done so many before...CXs were past masters of the art of doing this to you. Also, check for any small leaks on the return side of the cooling system as often, this was where the air came from in the first place.[:p][}:)][B)]
Alan S [:D]

shaunthesheep · Unread post by **shaunthesheep** » 06 Jul 2003, 22:38

alan,
bleed the coolant system, didn't find any air![:0] so think i will leave this as it is for th moment, unless it rears its ugly hear again!!, hope not[:p]
dom

Unread post by **alan s** » 07 Jul 2003, 03:30

Dom,
I'm probably telling you something you already know, but always be sure to have the heater opened in the hottest setting when bleeding the coolant; air locks have a nasty habit of hiding in heater matrixs which is sometimes the reason the matrix fail due to the increased pressure more than corrosion.
Alan S

algieuk · Unread post by **algieuk** » 07 Jul 2003, 17:10

Remember it is a 2 speed fan with the speeds cuttin gin at different temperatures. The fan might be operating only on the high speed (the low speed having failed).

shaunthesheep · Unread post by **shaunthesheep** » 07 Jul 2003, 21:28

does anyone know at what temp the fan should cut in, both at low speed & high speed??
dom

Unread post by **Jon** » 07 Jul 2003, 21:53

The temps will be stamped into the sensor.If its the blue one with 2 terminals I think the temps are 92 and 97.

vanny · Unread post by **vanny** » 07 Jul 2003, 21:59

On the subject of rad sensors, is there any way to retro fit one?? Can i just fit one into a pipe and does the water have to be flowing over the sensor?? Cant fit one into the rad anymore

At the moment its running with the fan (singular for now) running on full tilt.

AndersDK · Unread post by **AndersDK** » 07 Jul 2003, 22:58

Vanny -
What's the problem fitting a new sensor in your rad ?
The sensor HAVE to sense the actual water temperature - approx opposite to the rad's hot water inlet.
You may DIY a pipe with sensor fitted - then insert this pipe in the rad's bottom hose - but then the sensor MUST have a lower cut-in temp.

vanny · Unread post by **vanny** » 07 Jul 2003, 23:44

Well i had to cut a sensor in half to plug up the hole, there is pretty much NO room between the rad and the alternator. Its a good job there isnt too much movement in the engine or id already have major problems. Any ideas what the cut in temp is for the na diesel BX? Probably gonna rewire the whole lot with a fail safe switch in the cab, once the wate temp sensor is hoked up and proven accurate!

algieuk · Unread post by **algieuk** » 08 Jul 2003, 01:44

You can get sensors that work with retro-fit electric cooling fans (kenlowe used to do them). They fit into the radiator top hose (the wires come out through the end of the hose, and for some strange reason they don't leak). Haven't seen one in a long time but I'm sure they are still available.

algieuk · Unread post by **algieuk** » 08 Jul 2003, 01:46

Oh, and if you do fit one back in your rad, the BX ones fit OK and have much sturdier terminals on them.

AndersDK · Unread post by **AndersDK** » 08 Jul 2003, 02:21

Vanny -
The cooling spec on a N/A diesel :
Thermostat : opens at 82/fully open at 93
Fan sensor switch : Low cut-in 86-90/high cut-in 90-94
Panel warning : early 103-107/ emergency 110-114
All figures deg. Celcius.
The switch cut-in range is caused by the waxstat principle used in the sensors.
Any electronic (solid state/semiconductor) sensors may give way more welldefined cut-in temps - easy to find as RadioShack/Maplin kits - or DIY if you're in electronics. The sensor elements can readily be build/moulded into the original sensor housings.
You MUST use at least an industrial Class 2 (prooven 2% full scale accuracy) temp gauge when testing the actual temperatures on your engine/cooling system - never rely on standard car fittings.