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#1
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No A/C - need ideas
1992 LS-L - I've owned for a couple of weeks...
I have tried to diagnose my A/C system and am out of ideas. Here's what I know/have done: 1. Fuses and wires to compressor relay have continuity and power is at the correct leads. Compressor will not kick in without jumping it. 2. According to AllData, The WB wire from the ECU to the relay (pin #8, connector B60) is supposed to be at battery level when the ECU wants the compressor off, and go to ground when it wants the compressor on (but it never goes to ground). If I disconnect the WB wire from ECU to the relay, and use a jumper to ground the relay the compressor kicks in - so relay and other wiring is OK, but bought and tested another relay just to be sure) 3. Security system and cigarette lighter not working, but everything else (beside A/C) is now working fine (including visor vanity lights). Engine/transmission performance is good (20 mpg around town). No blinking dash lights, no stored codes on those things I can retrieve at home. 4. Hi/Low sides of A/C compressor test within limits, passed professional leak test, previously converted to R-134, no R-12 present. 5. No errors on climate control internal diagnostic routine. Climate system responds correctly in every way except to turn on compressor, i.e., heat, defroster, door actuators (where air blows out top/bottom), ambient sensor, sunload sensor, etc. all work properly. 6. ECU gets proper voltage signal from climate unit - battery level when A/C should be on, no signal when A/C should be off. 7. Throttle position sensor, trinary switch, water temp sensor, all working properly. 8. ECU turns on fans at radiator (jumper the trinary and it even correctly turns them up a notch), and the climate system sets interior fan speed correctly based on difference between dash setting and interior temp (higher fan speed if there's a large difference). 9. Have tried removing battery leads and touching them together, also tried leaving them off overnight. Removed ECU connector and reseated. 10 Didn't test evaporator or refrierant sensor, but as I said Climate control module is sending correct signals to the ECU when the A/C should be on or off. Have run out of ideas except replacing the ECU. Ideas (any) solicited. Want to gain good karma? Have a spare ECU that correctly controls the A/C (even if it has some other problem) so I could test my system. I'll gladly pay to/from postage. Replacing the ECU is simply too big an expense just to find out the problem is somewhere I've overlooked. I live in Florida, and 4/60 works for now, but the temps (and my frustration) are rising. tia, lee |
#2
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If you ran 60/4 or 4/60, it will cool you down. I'll crank out some ideas on this in a bit. Worst case, I'll sell you my AC unit -- It comes attached to a 94L though. Cost: for you, 3500
Lwin
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Lwin M. Maung (Member # 147) Current SVX: • NONE Previous SVXes: •1994 LE Barcelona Red 107k • 1992 LS-L Pearl White 143k • 1994 LSi Bordeaux Pearl 220k • 1992 LS-L Ebony Pearl 184k • 1992 LS-L Liquid Silver 145k • 1992 LS-L Liquid Silver 102k • 1992 LS-L Ebony Pearl 123k Other current cars:•2001 Jeep Grand Cherokee Black If at first you don't succeed, CHEAT!
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#3
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I'd install a temporary switch to the relay until I ran across a 'known good' ECU for testing. Might as well chill while waiting...
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ASE Certified Master Automotive Technician w/L1. ASE Certified Master Medium/Heavy Truck Technician. Certified EVT (Emergency Vehicle Technician) |
#4
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Wow! Very Thurough diagnosis. Everytime I thought to myself "Oh, try this" you listed it in the next section.
I agree that it is possibly the ECU. Or it could be that the ECU is kicking the AC out because of another sensor. What kicks out the AC? That I don't know for sure. I'm pretty sure that when you floor it the AC kicks out. That may be from the TCU sending a power mode signal to the ECU? I assume there are other things that would cut out the AC, High Engine temp, limp home mode, etc. Doug
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1992 LS Touring (6/91) - Currently undergoing a five speed swap Black over Claret with spoiler; 235,000 miles; Mods: 2002 Legacy 5 speed, ACT Pressure Plate, Excedy Clutch, Short Throw Shifter, Aussie Powerchip 1992 LS Touring (6/91) Black over Claret with 2.5" setback spoiler; 202,000 miles; Mods: B&M Cooler 1994 LSi (4/93) Bordeaux Pearl; 198,000 miles; Mods: Weight reduction. 1969 Mustang GT Convertible 1970 Mustang Convertible 2000 Ford Excursion Sola lingua bona est lingua mortua. My Locker |
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