Re: Coupe/4Kq After-run fan

[Luis Marques <marques@rtis.ray.com>]

bd983@scn.org (SCN User) wrote:
> It is?? Now I _am_ confused. I have been told previously by other
> listers that my 84 4kq is acting _normally_ when the cooling fan turns
> off with the key. Is it supposed to run after shutoff?? Recently had a
> new fan installed and my mechanic says everything works like it
> should. Anybody  have the definitive word? 
> 
> clarkl

The quick and easy way to tell if your Coupe/4kq has the afrter-run fan feature
is to look for a switch with two wires on the rear of the valve cover, on the
exhaust side.  If it's there, you have it.  If it's missing, you don't.  I think
this was a mid-year production change somewhere in 1985, so some '85 cars may
have it and some may not, but I think all '86 and '87 cars do have the after-run
relay.  I don't think the 4-cyl. cars were ever fitted with this extra relay,
though.

The way it works is as follows:
   - If the engine is running, the "radiator fan relay" on the fuse
     panel controls the fan with inputs from the temperature switch on
     the bottom of the radiator and the AC high-pressure switch.

   - When the engine is shut down (ignition off), a separate "after-run
     relay" on the auxiliary relay panel under the dasboard controls the
     fan based solely on the temperature switch on the rear of the valve
     cover. It has a timer buit-in so that the fan doesn't run forever
     if the switch/wiring is defective.

The fix for the unfused circuit if you don't have the after-run relay is still
the same with the only difference that there is only one big 2.5mm red/black
wire going into the yellow plug under the fuse panel that needs to be relocated.

It may take a while for the switch on the valve cover to get hot after you shut
off the car, even if the fan was running with the ignition on.  So it may take
five minutes for the fan to turn on after shutdown, but it could be running on
and off for 15-20 minutes!  It serves to cool the engine compartment and the
engine, prolonging the life of all rubber and plastic pieces and preventing
vapor lock in the fuel injection lines.  Turbo cars get even hotter and that's
why they have a separate dedicated fan just for the injectors.

-Luis Marques
 '87 4kcsq