Radiator Fan Stuck on

[Bernard Littau]

Hi Eric,

There is a system on your car to run the radiator fan after the car is shut
down.  Known as the After-run feature, it runs when the car is shut down and
is "hot".  The electric water pump below the brake master cylinder is also a
part of this system, BTW, and should run when the radiator fan runs in
after-run mode.  This after-run system means that most of the circuitry
associated with the radiator fan is always electrically live.

As I understand the system, it runs when the radiator multifunction sensor
sees a certain temperature, and the car is shut down.  To prevent draining
the battery due to excessive running, like from a bad sensor, there is a
"relay" that only allows the system to run for 10 minutes.  I believe this
relay is in the relay box inside the passenger compartment below and to the
left of the steering wheel.

My guess is that this 10 minute relay is somehow bad, and is causing the
stage 1 fan relay to always turn on.  You might pull the after-run relay and
see if this shuts off the fan, and you might swap it for a known good one to
see what effect this has.  You should also check the multifunction temp
sender on the radiator -- it alone being bad should not cause the fan to run
forever, but it being bad could cause the radiator fan to run for 10 minutes
each time you shut down.

I'm guessing the heater fan always on is a separate issue -- the climate
controllers are known to flake out on these cars.

Best,

Bernard Littau
Woodinville, WA
'88 5ktq

>
> Ok, I need the collectives assistance........My new (to me) 1987 5KCSTQ
> has
> the following problem:
>
> The radiator fan stays on (Stage 1 I think) no matter what, car running or
> not, key in or not.
> The only way I can get it to shut off is to remove the reelay closest to
> the
> firewall.
> Wile the the reelay was removed I checked it for proper operation and it
> was
> fine.
>
> I then put the reelay back in (Fan comes on) and began disconnecting all
> the
> thermo switches and sensors I know of
> (Multi function 4 wire & 2 wire by radiator hose & Power steering pump as
> well as the Single wire switches by the Power steering pump under the
> waste
> gate) with no joy. The fan continued to run.
>
> Now I do not know if it is related, but the Heater Blower motor runs
> continuously as well, even if the climate control is turned off
> completely.
> The only diference between the Heater blower motor and the radiator fan is
> that the Heater Blower Motor will shut off when the key is removed from
> the
> ignition while the Radiator Fan runs until the reelay is removed.
>
>
> Any suggestions...........
>
>
> Thanks !!
>
>