'91 Camaro - Electric Fan Control

[Timothy J Burgess]

As Denis mentioned, the '90 - '92 F-body ECMs control only the primary
cooling fan, even though Tuner Cat displays turn on & turn off temperatures
for both fans.  The secondary cooling fan is controlled by the temperature
switch located in the passenger side cylinder head, with a turn on
temperature of 238 F, and is ORed with a pressure switch in the A/C liquid
line that closes when the R-12 pressure exceeds 232 psig.  The primary
cooling fan is controlled solely by the ECM, with a stock turn on
temperature of 230 F if the A/C is off, and lower if the A/C is on, under
certain conditions.

Tim Burgess

Ken Richardson wrote:

> Does anyone on this list have any experience working with '91 GM F-body
> ECMs, specifically the fan on/off temperatures?
>
> Here's my problem. We installed a 383 stroker in a '91 Camaro and have
been
> burning EPROMs to correct the fuel mappings etc. Everything is working
well
> except I can't seem to get the fans to turn on and off when I want them
to.
> The first thing that happened is the fans reversed, Fan #2 was coming on
> first, then Fan #1. They were coming on around 210 degrees even when I
set
> them to 180 and 200 respecively. Then I burned an EPROM with both fans
set
> to 190....now Fan #1 doesn't come on at all and fan #2 comes on at 210.
>
> I'm using the Tuner CAT program to modify my EPROMs. Could this be my
> problem? Ideas? Does anyone have a wiring diagram of the fan circuitry?
>
> Thanks
> Ken R.

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