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No A/C, No Cooling Fans - Advice Needed

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  • #1

    No A/C, No Cooling Fans - Advice Needed

    I have a '96 Z28 that doesn't have working A/C or cooling fans. The problem with both started at the exact same time. No repairs or maintenance on the car was being performed at the time, so it's likely a failure.

    My friend and I fully tested the A/C circuit. The input signal is making it to the PCM, but the PCM is not grounding the circuit on the backend. When manually grounding the circuit, the A/C kicks on, which of course triggers the cooling fans. Mistakenly I stopped at this point and assumed I had a bad PCM. Replaced the PCM only to still have the same problem.

    Call me dumb, but I was unaware until reading in this forum that the cooling fan circuit apparently has an input to the A/C circuit to help prevent overheating. I just find it strange that the A/C diagram doesn't show an input from the cooling fan circuit.

    I have yet to have time to track the cooling fan circuit, but I'm seeking advice.

    Has anyone seen this problem or know where the problem might be located that could be causing both failures?

    Thanks in advance.
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  • #2
    If there isn't enough freon in the system the low pressure switch will keep the compresor from coming on (and the fans of coarse).
    2002 Electron Blue Vette, 1SC, FE3/Z51, G92 3.15 gears, 308.9 RWHP 321.7 RWTQ (before any mods), SLP headers, Z06 exhaust, MSD Ignition Wires, AC Delco Iridium Spark Plugs, 160 t-stat, lots of ECM tuning

    1995 Z28, many mods, SOLD

    A proud member of the "F-Body Dirty Dozen"

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    • #3
      I failed to mention that the cooling fans never work. The car will overheat in stop and go traffic.

      I would think the low freon would not play a factor in the cooling of the engine, but I've been wrong many times.

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      • #4
        Just a guess, but I think the problem lies in the fans, not the A/C. Think about it, the a/c needs the fans on to fuunction properly. If the feed from the fans to the a/c is dead, it would not allow the circuit to close and thereby keep the a/c off.

        Could a relay be the culprit?
        Al 96 Ram Air T/A
        Mods: Build # 784 * Hotchkis STB * SFCs * Borla cat back w/QTP cut-out * AS&M/RK Sports Mid-length headers w/single CAT * Koni SA shocks on lower perch w/ lowered rear * Strano Hollow front & rear antisway bars * 1LE front/rear springs * 1LE aluminum driveshaft * Strange 4.10 gears w/ Zexel Torsen diff. * ARP bearing cap studs & aluminum diff cover* J&M Hotpart poly/poly rear LCAs and poly/poly panhard bar * RAM Powergrip clutch w/ LT4 PP and RAM billet Al flywheel * C5 Z06 brakes * C6 Z06 wheels * Spohn T/A * Spohn DS Loop * fully custom interior w/ custom audio

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        • #5
          I've swapped around several relays, both of which included A/C compressor and cooling fans. There was no change.

          It does make sense now that I know the A/C can be kept off by the fan circuit. I just wish I would've learned that prior to buying the PCM and cals.

          That's what I get for being impatient I guess.

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          • #6
            Originally posted by madams137
            I failed to mention that the cooling fans never work. The car will overheat in stop and go traffic.

            I would think the low freon would not play a factor in the cooling of the engine, but I've been wrong many times.
            I am having the EXACT same problem now also (with the fans not coming on at all /AC works), But thank goodness I have a fan switch mod to cool the emngine down in stop and go traffic.
            1997 Z-28 70K - 52 mm Edelbrock Throttle Body, Flowmaster series 80, K&N Cold Air intake, NGK Iridium Plugs TB Bypass, B&M Ripper shifter, Kenwood Head Unit, 2 MTX Amps,Clarion DVD Player , 2 10" MTX subs, 2 MTX 6x9's, 4 MTX 6.5's, 4 Kenwood 1" tweeters .

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            • #7
              I spoke to my neighbor for ya'...He's a GM mechanic. He agreed...if the fans aren't working, the a/c will not engage the compressor. You need to diagnose why the fans are shot.
              Al 96 Ram Air T/A
              Mods: Build # 784 * Hotchkis STB * SFCs * Borla cat back w/QTP cut-out * AS&M/RK Sports Mid-length headers w/single CAT * Koni SA shocks on lower perch w/ lowered rear * Strano Hollow front & rear antisway bars * 1LE front/rear springs * 1LE aluminum driveshaft * Strange 4.10 gears w/ Zexel Torsen diff. * ARP bearing cap studs & aluminum diff cover* J&M Hotpart poly/poly rear LCAs and poly/poly panhard bar * RAM Powergrip clutch w/ LT4 PP and RAM billet Al flywheel * C5 Z06 brakes * C6 Z06 wheels * Spohn T/A * Spohn DS Loop * fully custom interior w/ custom audio

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              • #8
                You can jumper the fan relays on the drivers side under the hood to see it the fans are working. The relays have a diagram on them to show the way power flows. If they come on, then at least you know its not a power problem.
                96 Camaro Z28/A4,Vortech elbow,Moroso CAI,Flowmaster.Addco PHR,LCA,160* Stat,pcmforless,1LE Driveshaft,1LE A/C delete pulley,1LE Front sway bar,Strut brace,sub frames, LT4 knock module,255 lph pump,Cutout,

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                • #9
                  Never mind the advice I went back and reread your oniginal post. I see that you did get the fans to come on.
                  96 Camaro Z28/A4,Vortech elbow,Moroso CAI,Flowmaster.Addco PHR,LCA,160* Stat,pcmforless,1LE Driveshaft,1LE A/C delete pulley,1LE Front sway bar,Strut brace,sub frames, LT4 knock module,255 lph pump,Cutout,

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                  • #10
                    Where does the pcm get the signal to turn on the fans when the car is getting too hot. Is it the sensor on the water pump? Could be something to look at. If the pcm does know the car is getting hot, It wont turn on the fans.
                    96 Camaro Z28/A4,Vortech elbow,Moroso CAI,Flowmaster.Addco PHR,LCA,160* Stat,pcmforless,1LE Driveshaft,1LE A/C delete pulley,1LE Front sway bar,Strut brace,sub frames, LT4 knock module,255 lph pump,Cutout,

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                    • #11
                      Thanks for the feedback. I'll be devoting some time this weekend to testing the fan circuit.

                      I'll post back what I find.

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