ECM's and Air Conditioning

[rr]

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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