Need help troubleshooting AC not working
Thread Starter
Cruising
Joined: Jun 2012
Posts: 13
Likes: 0
From: Las Vegas NV
Need help troubleshooting AC not working
Need help troubleshooting AC not working on my 2000 C5.
AC was working fine, last week, the dashboard flickered like an electrical short then the AC stopped working. The compressor clutch engages, ac button light blinks twice then stays on, air blows thru the vents but at ambient temperature. No apparent freon leak under the hood. No AC codes on the DIC when pulling codes.
Any ideas?
AC was working fine, last week, the dashboard flickered like an electrical short then the AC stopped working. The compressor clutch engages, ac button light blinks twice then stays on, air blows thru the vents but at ambient temperature. No apparent freon leak under the hood. No AC codes on the DIC when pulling codes.
Any ideas?
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Well,,, unless you destroyed the Head Unit Electronics, I'm at a loss... 
Can you put your ear to the main center vent and while everything is QUIET, change the temp **** and see if you can hear the temperature door actuator motor spin?
Can you put your ear to the main center vent and while everything is QUIET, change the temp **** and see if you can hear the temperature door actuator motor spin?
Thread Starter
Cruising
Joined: Jun 2012
Posts: 13
Likes: 0
From: Las Vegas NV
Bill,
Thanks, I haven't tried that, I will check that out and post back. The head unit looks and works normal, turns off/on changes temp and modes.
Is there a fuse or relay for the temp door actuator motor?
Thanks, I haven't tried that, I will check that out and post back. The head unit looks and works normal, turns off/on changes temp and modes.
Is there a fuse or relay for the temp door actuator motor?
Safety Car
Joined: Mar 2017
Posts: 3,771
Likes: 940
From: Orlando Florida
"No apparent freon leak under the hood"?
Why apparent? My leak is pretty obvious, but when it's empty the A/C light flashes and goes back out.
Seems to me I've read the ambient temp sensor is necessary for operation -- do you have real or fixed ambient air indications?
Why apparent? My leak is pretty obvious, but when it's empty the A/C light flashes and goes back out.
Seems to me I've read the ambient temp sensor is necessary for operation -- do you have real or fixed ambient air indications?
Last edited by redzg; May 27, 2017 at 09:51 PM.
Advanced
Joined: Dec 2016
Posts: 79
Likes: 3
Check your Compressor is turning on.. if it isn't bypass relay under hood pull relay for ac and bridge it will force compressor to take your freon. You can add 1 can of freon should be enough to get ac compressor compress gas. Seems to me need freon. I had same problem and only way get compressor take the freon ..I had to also replace low side valve was leaking ..
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Drifting
Joined: Sep 2007
Posts: 1,649
Likes: 50
From: Goldsboro NC
Thread Starter
Cruising
Joined: Jun 2012
Posts: 13
Likes: 0
From: Las Vegas NV
No sound from the actuators, tried changing modes/redirect air to foot and windshield and that does work but still no cold air.
The compressor does turn on, clutch engages when turned on a the AC head unit. I can see it spin compared to when the AC is off.
I say no apparent leak as in trying to say nothing obvious. But the compressor turns on and stays on.
The compressor does turn on, clutch engages when turned on a the AC head unit. I can see it spin compared to when the AC is off.
I say no apparent leak as in trying to say nothing obvious. But the compressor turns on and stays on.
Thread Starter
Cruising
Joined: Jun 2012
Posts: 13
Likes: 0
From: Las Vegas NV
Bill,
is the "instrument panel electrical center" same as the fuse panel under the dash on the pass side?
That is the only fuse I see on that diagram, please correct me if I'm wrong but if that is the only one, if that 10A fuse was out then the HVAC unit would not work at all and mine is working.
The problem started right after the dashboard flickered like it was a short. What AC related part would fail related to a short on dashboard? All else on dashboard works.
is the "instrument panel electrical center" same as the fuse panel under the dash on the pass side?
That is the only fuse I see on that diagram, please correct me if I'm wrong but if that is the only one, if that 10A fuse was out then the HVAC unit would not work at all and mine is working.
The problem started right after the dashboard flickered like it was a short. What AC related part would fail related to a short on dashboard? All else on dashboard works.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Bill,
is the "instrument panel electrical center" same as the fuse panel under the dash on the pass side?
That is the only fuse I see on that diagram, please correct me if I'm wrong but if that is the only one, if that 10A fuse was out then the HVAC unit would not work at all and mine is working.
The problem started right after the dashboard flickered like it was a short. What AC related part would fail related to a short on dashboard? All else on dashboard works.
is the "instrument panel electrical center" same as the fuse panel under the dash on the pass side?
That is the only fuse I see on that diagram, please correct me if I'm wrong but if that is the only one, if that 10A fuse was out then the HVAC unit would not work at all and mine is working.
The problem started right after the dashboard flickered like it was a short. What AC related part would fail related to a short on dashboard? All else on dashboard works.
When you say SHORT, think of BLOWN fuse, smoke, fire and flames.
Intermittant connection, poor connection, bad ground ect.. would be more on the line of whats happening.
Check the fuse and make sure that it is solid in the fuse slot. I break an old fuse in half and insert one blade into each one of the fuse slots. Called a push pull test. The fuse blade should see equal amounts of GRIP on the blade of the test fuse blade during insertion and removal.
If the HVAC Head is functional, I dont see power or ground to the head unit being an isssue.
If the logic in the module is bad, it just plain wont work.
Some more HVAC Schematics
Thread Starter
Cruising
Joined: Jun 2012
Posts: 13
Likes: 0
From: Las Vegas NV
Finally got around back to it, just before we start the 110+ degree week next week!
Bill, thanks for the schematics, I found and checked all the fuses, all are ok. I also got me the Haynes AC book and did some reading.
Got my manifold/gauges got them connected here's what it read.
Engine off - Low side = 120 High side = 135
Engine on - Low side = 110 High side = 135
From what I read in the book, either the expansion valve is stuck or compressor is bad. Before the AC stopped cooling the compressor was a bit noisy but it was blowing cold then suddenly it just stopped blowing cold. My guess, its the compressor. Now I got to get the system drained so I can work on it. I'm looking at which compressor/accumulator/orifice tube/oil kit to buy to install.
Bill, thanks for the schematics, I found and checked all the fuses, all are ok. I also got me the Haynes AC book and did some reading.
Got my manifold/gauges got them connected here's what it read.
Engine off - Low side = 120 High side = 135
Engine on - Low side = 110 High side = 135
From what I read in the book, either the expansion valve is stuck or compressor is bad. Before the AC stopped cooling the compressor was a bit noisy but it was blowing cold then suddenly it just stopped blowing cold. My guess, its the compressor. Now I got to get the system drained so I can work on it. I'm looking at which compressor/accumulator/orifice tube/oil kit to buy to install.
Drifting
Joined: Sep 2007
Posts: 1,649
Likes: 50
From: Goldsboro NC
Finally got around back to it, just before we start the 110+ degree week next week!
Bill, thanks for the schematics, I found and checked all the fuses, all are ok. I also got me the Haynes AC book and did some reading.
Got my manifold/gauges got them connected here's what it read.
Engine off - Low side = 120 High side = 135
Engine on - Low side = 110 High side = 135
From what I read in the book, either the expansion valve is stuck or compressor is bad. Before the AC stopped cooling the compressor was a bit noisy but it was blowing cold then suddenly it just stopped blowing cold. My guess, its the compressor. Now I got to get the system drained so I can work on it. I'm looking at which compressor/accumulator/orifice tube/oil kit to buy to install.
Bill, thanks for the schematics, I found and checked all the fuses, all are ok. I also got me the Haynes AC book and did some reading.
Got my manifold/gauges got them connected here's what it read.
Engine off - Low side = 120 High side = 135
Engine on - Low side = 110 High side = 135
From what I read in the book, either the expansion valve is stuck or compressor is bad. Before the AC stopped cooling the compressor was a bit noisy but it was blowing cold then suddenly it just stopped blowing cold. My guess, its the compressor. Now I got to get the system drained so I can work on it. I'm looking at which compressor/accumulator/orifice tube/oil kit to buy to install.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Finally got around back to it, just before we start the 110+ degree week next week!
Bill, thanks for the schematics, I found and checked all the fuses, all are ok. I also got me the Haynes AC book and did some reading.
Got my manifold/gauges got them connected here's what it read.
Engine off - Low side = 120 High side = 135
Engine on - Low side = 110 High side = 135
From what I read in the book, either the expansion valve is stuck or compressor is bad. Before the AC stopped cooling the compressor was a bit noisy but it was blowing cold then suddenly it just stopped blowing cold. My guess, its the compressor. Now I got to get the system drained so I can work on it. I'm looking at which compressor/accumulator/orifice tube/oil kit to buy to install.
Bill, thanks for the schematics, I found and checked all the fuses, all are ok. I also got me the Haynes AC book and did some reading.
Got my manifold/gauges got them connected here's what it read.
Engine off - Low side = 120 High side = 135
Engine on - Low side = 110 High side = 135
From what I read in the book, either the expansion valve is stuck or compressor is bad. Before the AC stopped cooling the compressor was a bit noisy but it was blowing cold then suddenly it just stopped blowing cold. My guess, its the compressor. Now I got to get the system drained so I can work on it. I'm looking at which compressor/accumulator/orifice tube/oil kit to buy to install.
Intermediate
Joined: May 2024
Posts: 25
Likes: 0
2003 Chevy Corvette AC
My 2003 Chevy Corvette is having AC problems. I’ve replaced the fuse in the relays and my head unit is fine because I just bought a different one. I’ve changed the air temperature sensor. The clutch turns over cause I’ve gotten my other mechanic to wire something up to see if the compressor works and it’s turned over and it’s blown cold air, but for some reason the head unit when I click the button it starts to blink and no cold air will come out and it’s just straight hot air any solutions.
in my temperature on the exit temp keeps reading 69° when it’s 70-80+ degrees outside
in my temperature on the exit temp keeps reading 69° when it’s 70-80+ degrees outside
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,611
Likes: 4,061
From: Cape Coral, Florida
My 2003 Chevy Corvette is having AC problems. I’ve replaced the fuse in the relays and my head unit is fine because I just bought a different one. I’ve changed the air temperature sensor. The clutch turns over cause I’ve gotten my other mechanic to wire something up to see if the compressor works and it’s turned over and it’s blown cold air, but for some reason the head unit when I click the button it starts to blink and no cold air will come out and it’s just straight hot air any solutions.
in my temperature on the exit temp keeps reading 69° when it’s 70-80+ degrees outside
in my temperature on the exit temp keeps reading 69° when it’s 70-80+ degrees outside
Your other mechanic must have “jumped” the load side of the relay to allow the AC clutch to engage and now provide proper cooling so I’d have your other mechanic if he has any electrical knowledge to check the “control” side of the relay (pins 85 and 86) with a test light and also check your other inputs like the AC pressure sensor with a scan tool (checking voltage or pressure data PIDS) to see if it is working properly…if the pressure sensor or wiring is bad the AC clutch will not engage…just because you changed the ambient air temp sensor or HVAC control head doesn’t mean it’s good or the wiring is OK…if the other mechanic can’t diagnose it take it to your regular mechanic…having a scan tool that can read HVAC DTC’s will help and not some cheap $20 code reader which will not…he can also use the cars built in code reader on the DIC…if both mechanics can’t put their heads together and figure it out take your car to an auto electric or a diagnostic shop…most mechanics are very poor at electrical..a good diagnostic tech can diagnose any system on any car.
Last edited by C5 Diag; May 29, 2024 at 03:56 AM.