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Author Topic: PCM to get my A/C working  (Read 193 times)

greywolf27030

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    • 88 Festiva, 91 Capri, 91 XR2
PCM to get my A/C working
« on: September 01, 2018, 10:25:15 AM »

It appears I have a PCM problem.  My A/C compressor won't turn on.  When you ground the white A/C relay wire(PCM wire), it comes on fine and blows cold.  I'm guessing a PCM problem.  The cruise control also quit working.  Maybe also a PCM problem.  Does anyone have any experience with this?  The car is a 91 XR2.  Does anyone have a spare XR2 PCM?

Jack Byrd
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Rocketman

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    • 91 BPT AWD Capri & 1991 XR2
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Re: PCM to get my A/C working
« Reply #1 on: September 03, 2018, 07:09:43 PM »

I don't think the PCM controls these items. Particularly the cruise control. It has its own module under the dash
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1.8L Turbo All Wheel Drive Capri... the "GTXR2"


blueamber

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Re: PCM to get my A/C working
« Reply #2 on: September 04, 2018, 12:20:06 AM »

That white wire is from the PCM to turn on or off the AC clutch if a bad pressure condition is sensed by the AC clutch cycling pressure switch.  If the pressure is too high you've got something wrong in the system that must be fixed, too much freon, clogged evap, something... If the pressure checks out OK (not too high, not too low) then maybe bad is the PCM, wiring, pressure switch, AC module, could be lots of things.
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greywolf27030

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    • 88 Festiva, 91 Capri, 91 XR2
Re: PCM to get my A/C working
« Reply #3 on: September 04, 2018, 10:01:34 AM »

Pressure is fine.  The only way the clutch will function is when you ground the white wire to the PCM.

Thanks, Jack Byrd
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greywolf27030

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    • 88 Festiva, 91 Capri, 91 XR2
Re: PCM to get my A/C working
« Reply #4 on: September 04, 2018, 10:05:58 AM »

I don't think the PCM controls these items. Particularly the cruise control. It has its own module under the dash

So I"ve got two problems, crap.

Thanks....lol
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greywolf27030

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    • 88 Festiva, 91 Capri, 91 XR2
Re: PCM to get my A/C working
« Reply #5 on: September 04, 2018, 05:53:14 PM »

I interpret the schematic as the A/C relay is activated by the white wire that goes to the PCM.  This is reinforced by the fact that the compressor operates when you ground that white wire.

Jack Byrd
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belleaudb

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  • Posts: 37
    • 92 XR2
Re: PCM to get my A/C working
« Reply #6 on: September 04, 2018, 08:38:33 PM »

The PCM will disengage the a/c compressor at full throttle.  Is your throttle position sensor working properly?
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greywolf27030

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    • 88 Festiva, 91 Capri, 91 XR2
Re: PCM to get my A/C working
« Reply #7 on: September 05, 2018, 09:42:04 AM »

Haven't experienced any drivablity problems.

Thank, Jack Byrd
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Rocketman

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Re: PCM to get my A/C working
« Reply #8 on: September 07, 2018, 12:25:27 AM »

Can you check continuity on the pressure switch to see if the switch is seeing proper pressure?

None of my Capris have ever had working ac, I removed most of it, so I'm not terribly familiar with it.
If you want I gave give the schematics a dive and see what that to expect on that wire
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1.8L Turbo All Wheel Drive Capri... the "GTXR2"


greywolf27030

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    • 88 Festiva, 91 Capri, 91 XR2
Re: PCM to get my A/C working
« Reply #9 on: September 07, 2018, 05:54:18 PM »

Thanks, I found the manual on the A/C and the first step seems to be check for power on the white wire at the PCM.  I'm trying to arrange to get the manual printed so I can start troubleshooting.

Jack Byrd
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