[V6-12v] Radiator Fans not switching in correctly...

[Tom Christiansen]

James,

There are three thermosensors/switches in the system:

1) Engine coolant temperature sensor (ECT) in the hard coolant line by
the EGR valve. Port side, aft of engine. This is used by the ECU.

2) Temperature sensor, switch on the starboard, aft side of engine by
the ISV. This feeds the gauge on the instrument cluster as well as
turns on the high-temp warning light.

3) Thermoswitch in the bottom starboard corner of the radiator. This
one controls the rad fans.

Even though I have A/C, my car (1994 90 S, AAH engine) only has one
rad fan. The speed of it is controlled by the thermoswitch as well as
a resistor pack mounted on the port side, forward subframe. More or
less directly under the battery. If the resistor pack is fried, the
fan will usually kick on at high-speed only. Resistors normally fail
open so you'll get no fan action until the trip point for high-speed
is reached. My rad fan turns on at low-speed when  I turn on the A/C.

Hope this helps.

Tom

On 8/28/06, James Whitehouse <james_whitehouse1 at yahoo.co.uk> wrote:
> Guys,
>
> Anyone know the fault finding procedure for the radiator fans on this
> engine? My engine manual doesn't cover this, for some reason (why?). I only
> have fault finding for the ignition system, which covers the coolant temp
> sender (G62), which feeds the Control Unit.
>
> However, I know that there are two other 'thermo switches', one being the
> thermo switch that plugs in on the bottom left of the radiator housing
> itself, and another (F76) which sits on the large coolant pipe on the left
> rear of the engine (as you look at it from the front of the engine bay)
> which I know feeds the dashboard temp gauge, but I believe may also have
> something to do with the rad-fan timing, etc.
>
> There's also a relay or two in the fuse box and a couple of fuses, but I
> don't have enough detail on what the two thermo-switches actually do to know
> where to start.
>
> The symptoms are as follows:
>
> - Engine waits until it's one mark beyond the 'normal' temp mark (the more
> distinctive 'centre' thicker splodge of white mark on the dash), then both
> fans kick in (full speed?) for about 20 seconds. They then turn off again
> without having cooled the engine.
>
> I'm guessing that a) first speed fans aren't working, as I remember them
> kicking in before that mark, and staying on longer, then 'speed 2' kicking
> in when sitting in traffic for ages, bringing it down to 'speed 1' temp.
>
> If anyone has info, or fault finding for this system, could you let me know
> please?
>
> TIA
>
> James
>
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