Cooling fan Operation

[Roger Heflin]

Bruce,

I can confirm on the 93 Z that both fans will turn on if it hits hot
enough.  It is documented in the helm (GM) manual I have for my car.
Knowing GM I would expect that they do this on all vehicles with two fans.
The book says 108C on, at 105C the fan will turn off.  The second fan
comes on at 113C and off at 110C.


Which ecm and in what car are you looking at?  I have read out my proms
for my 93 Z28.  From the diffs I have determined where some of the Open
to closed loop throttle positions values are.  I have worked out the
formats (value/256) is the percent, and the numbers seem to match what the
tuner told me the original settings were and what he changed them to.  The 
part that I cannot really figure out is that there are several numbers in
a row representing values at different rpms.  Does anyone know what rpms
the ECM's generally start at? and what the step size is, and where it
ends?

				Roger

On Wed, 12 Aug 1998, Bruce Plecan wrote:

> After starring at the wirez too much today, I think I saw the problem
> someone was asking about.
>   There are two fan temps setting in that ecm.  One is the primary
> as you would expect.
>    But, the secondary has several optional modes of operation.
> A/C on, turns the fan on for the cooling the condener, and there
> is a high pressure switch.  Then there is the thermal switch mounted in the
> engine, and lastly the the ecm controlled temp option for it.
> But, with nothing else triggering it, it (ie not A/C) given long enough it
> should trigger on, if the primary fan can't keep up with the temp.
>    Once I get the bench ecm running I'll verify this as fact, right now,
> just
> that's how it looks.
> Cheers
> Bruce
> 
>