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Old Aug 13, 2016 | 08:16 PM
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Default ac has not power

I have a 98 c5 and I'm about to pull all my hair out trying to figure out whats going on with my air condition stop working,,,,no power... checked all fuses and had control unit checked... all passed....control unit lights up but nothing happens when power button pushed. Can anyone help?
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Old Aug 13, 2016 | 08:41 PM
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Did you pull the codes?
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Old Aug 13, 2016 | 08:56 PM
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Little more info, but if it is low on Freon it won't run (compressor)????
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AC System Diagnostics.pdf (2.56 MB, 130 views)
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Old Aug 13, 2016 | 09:32 PM
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Ok now check engine lights is on along with ABS and traction control... pulled codes
P0705 C
C2121 C
B0432 H C
B2262 H
B2264 H
B2263 H
B2265 H
99 HVAC NO COMM
P1571 H
P1644 H C
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Old Aug 13, 2016 | 09:46 PM
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Originally Posted by Henson99
Ok now check engine lights is on along with ABS and traction control... pulled codes
P0705 C
C2121 C
B0432 H C
B2262 H
B2264 H
B2263 H
B2265 H

99 HVAC NO COMM
P1571 H
P1644 H C
Is your battery fully charged and do you have good connections?
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Old Aug 13, 2016 | 10:48 PM
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Originally Posted by JR-01
Is your battery fully charged and do you have good connections?
Yes, I replaced battery and showing 15vlts, Ive read others thread mentioning ignition switch and I did show 1 time at start up service lock column but haven't anymore, could that be the problem
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Old Aug 14, 2016 | 09:23 AM
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A fully charged battery should be 12.6 volts at the terminals. Your 15v must be the gauge showing alternator output.. With all those codes I would first make sure battery is fully charged(trickle charger) and then move on from there. New batteries aren't always fully charged. I discovered early on with these cars, low voltage raises havoc with the electronics.
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Old Aug 14, 2016 | 09:45 AM
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Looking at your posted codes and then reading up on the ones posted, they're all over the place. Some related to traction control, ABS, etc but the one that sticks out is the HVAC No Comm. Without communication to the HVAC head unit, nothing will happen when you push a button, just like you said. It would appear from the posted codes that you have a bad or loose connection somewhere in the system. Could possibly be a bad head unit. I'd start by checking the grounds and also checking fuses 18 and 27 in the passenger foot well.
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Old Aug 14, 2016 | 05:53 PM
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Originally Posted by CactusCat
Looking at your posted codes and then reading up on the ones posted, they're all over the place. Some related to traction control, ABS, etc but the one that sticks out is the HVAC No Comm. Without communication to the HVAC head unit, nothing will happen when you push a button, just like you said. It would appear from the posted codes that you have a bad or loose connection somewhere in the system. Could possibly be a bad head unit. I'd start by checking the grounds and also checking fuses 18 and 27 in the passenger foot well.
That's what I was thinking too....no comm no power....I had head unit tested and they said works fine....im knew too all this and may sound alitte naive but how do I go about checking grounds?
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Old Aug 14, 2016 | 06:05 PM
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Originally Posted by Henson99
That's what I was thinking too....no comm no power....I had head unit tested and they said works fine....im knew too all this and may sound alitte naive but how do I go about checking grounds?
I haven't been down that road yet, but I'll assume it's similar to cleaning the battery terminals. Just making sure everything is clean and making good contact.

Good Luck!
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Old Aug 14, 2016 | 11:16 PM
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Originally Posted by Henson99
That's what I was thinking too....no comm no power....I had head unit tested and they said works fine....im knew too all this and may sound alitte naive but how do I go about checking grounds?
Well, its definitely a learning experience but just take your time. I'm going to post a thread link that has a ton of great info including how to check your grounds and this is where I'd start.
https://www.corvetteforum.com/forums...tion-long.html Check your battery connections first then go from there. You're fixing to get intimate with your C5.
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