7747 A/C enable

[steve ravet]

Brent, I went home last night and took a look at my S-10, which has a
6965 from a '91 Caprice in it.  I was thouroughly confused by the
circuit diagram, which is as you described, and the troubleshooting
section of the service manual, which implies that the ECM grounds the
relay to turn on the compressor.  In fact the description of the circuit
says that the ECM energizes the relay to turn on the compressor.  I can
say for sure, from looking at the relay itself, that the clutch is
across terminals 30 and 87a of the relay, which are the normally closed
ones, which matches your description, which does seem backwards.

Have you tried hooking it up to see if it works?  From what I've seen of
my service manual it wouldn't surprise me if your 747 schematic is wrong
and it'll just work.

If it doesn't I think either rewiring the relay, or using the 747
harness and relay, is the best solution.  Remember that in the 747 part
of the code is in a PROM, and is unchangeable.  Only some of the code is
in the EPROM, so you might not even be able to get at the A/C code.

--steve

Brent Obermiller wrote:
> 
> Hi.
> 
> I got my V8 cal-pak, have burnt an 87 suburban Prom, and am ready to begin
> road testing and fuel/spark tweaking.  Now, this is a detail question. The
> 16136965 grounds the a/c relay to disable the Compressor while it appears
> that the 7747 grounds the A/c relay to enable the compressor.  For the sake
> of swappability, (i.e. not re-wiring) is there simple software 'fix' to
> invert the a/c enable? This contact is C2 on both ecm's.  Thanks.
> 
> -Brent
> 
> to reply directly
> mailto:ober_b at sssnet.com
> 
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-- 
Steve Ravet
steve.ravet at arm.com
Advanced Risc Machines, Inc.
www.arm.com