computer controlled A/C question

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Feb 24, 2008 | 08:28 PM

ls1nova71

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computer controlled A/C question

I'm wanting to run my A/C through the PCM, to control fans, step up idle, etc. My question is, is there any way of bypassing the pressure switch? Or does the PCM use pressure to control the fans, or just temperature? I'm using a 2001 camaro harness. My A/C is an R12 system and works so I really don't want to break the system open to add a place for the pressure sensor. Is this even possible or am I out of my mind for even thinking about it? Thanks in advance, Eric

Feb 24, 2008 | 08:58 PM

01WS6/tamu

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It works quite well. However, for the pcm to correctly control compressor and or fan operation it has to have the three wire pressure switch installed into the high side liquid line.

Feb 24, 2008 | 11:26 PM

ls1nova71

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That's what I was afraid of. But there isn't a way to make the PCM think the pressure is at an average psi? Does that make sense?

Feb 24, 2008 | 11:43 PM

busta9876

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The pressure sensor is a linear sensor, there should be a spec for pressure=volts somewhere...

Might have to get a sensor and test it with compressed air or something to see what the voltage output is. 3 wires, ground, 5 volt reference, and signal.

the programming for a 2000 camaro shows fan control by coolant temp, with different on points for a/c on or off...

Also has a/c pressor LOW SPEED FANS ON at 215 PSI and OFF at 190 PSI. & HIGH SPEED FANS, are ON at 248 PSI and OFF at 208 PSI.

I would normally think anytime a/c is on you would want airflow over the a/c condensor....so you could feed the PCM an AVERAGE pressure signal, and then make the cooling fans turn on with the a/c compressor clutch.

Feb 24, 2008 | 11:52 PM

ls1nova71

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Guess I'll just nix the idea and run a wire to the fan relay whenever the A/C is on. Should I use high speed fan relay or low? I've done that in the past, but I don't like the idea of the fans running all the time such as on the freeway. Unless I can find an adapter of some sort to go in place of the original Ford pressure switch.

Feb 29, 2008 | 07:35 PM

N21923

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I had a CNC shop make me an adapter for my RX7. Cost about $40, but it's right.

Feb 29, 2008 | 07:51 PM

G-Body

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Another option is available if you know someone who is adept at computer programming. The 99-01+? trucks do not use a variable resistance pressure switch, they use the old style on/off switch. I just jumped mine out. Now if you can get someone to set up your computer to be looking for the truck style pressure switch you can jump it out with a piece of wire. In order to do that I think that they would have to do a segment swap on the computer program. I know it is possible to do a segment swap for the transmission section (LS1 F-Body computer running a 4l80e trans) so I am Assuming that it would also be possible to do a segment swap for the A/C pressure sensor.