ECM's and Air Conditioning

[Scott Pearson]

Looking at the schematics, this car uses it for the 'parking maneuvers',
while the s/c ecm uses it for either the fan or the diagnostics. Not sure
about the last one, but that's my guess based on what you've said here.

Scott

----- Original Message -----
From: "rr" <RRauscher at nni.com>
To: <gmecm at diy-efi.org>
Sent: Tuesday, August 14, 2001 8:36 PM
Subject: Re: ECM's and Air Conditioning


> I'd like to talk in general about some of the inputs you mentioned. I've
> seen A/C head pressure used for ECM input for fan control. With high
> A/C pressure, the ECM turns the fan on. I've also seen it used for a
> body computer diagnostic. I've seen a system changed from R12 to
> R134 and the body/dash diag kept coming up with A/C failed.
>
> The P/S pressure switch is sometimes used to in conjection with a
> parking maneuver & the A/C. At low engine speeds and high P/S
> pressure the ECM will disable the A/C to prevent drivability issues.
>
> The above info may not apply to your issues. Then again, I hope it helps.
>
> BobR.
>
> sapearso at rockwellcollins.com wrote:
>
> > Getting about ready for the ECM swap on the 88 Toronado. Have a question
> > concerning the air conditioning. On the oringinal 1228253 ECM, the A/C
> > request is handled by the HVAC panel sending a request on the data line.
On
> > the 16141470, this request is a discrete input on pin BD11. Will the
> > 16141470 be capable of picking this up off the data line, or do I need
to
> > 'T' into the output from the BCM to the '+' side of the compressor
clutch
> > relay? The ECM provides the ground to this relay in both cases. The
> > 16141470 schematic shows that the '+' side of this relay coil is always
> > energized, while the BCM provides this signal on the Toronado.
> >
> > Next question, on the schematic for the 16141470, it shows a 'A/C head
> > pressure' which is supplied a ground by the A/C head pressure switch.
What
> > is this for? I don't see one on the schematic for the Toronado. The
> > Toronado also lists a power steering pressure switch, but it's not
listed
> > on the schematic for the 16141470.
> >
> > If anyone wants to see these schematics, email me offlist and I'll send
> > them to you.
> >
> > Scott
> >
>
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