View Full Version : HVAC blinks but no codes present
Matt B
10-24-2021, 02:29 PM
The headline says it all: I have a blinking HVAC LED short after starting the engine but there are no error codes present. A/C work well and I can't spot any other malfunctions.
Any ideas?
TX '90 ZR1
10-24-2021, 10:05 PM
Does the light blink over each button that is selected or just in the off position? Most common cause of blinking light, in my experience, is a code 9 low freon.
To start with I would disconnect the battery for a couple of minutes. Be sure and check the condition of the battery connections while you have them loose. A dirty battery connection can cause all sorts of issues with the electrical system.
:cheers:
GOLDCYLON
10-25-2021, 03:43 AM
Correct 9 out of 10 times the blinking light is low Freon condition. :cheers:
Matt B
10-25-2021, 08:11 AM
The flashing comes over each button, so also in those conditions where A/C is off.
When is that code 9 triggered? Before it quits working or when it's "too late"? I'm asking because cooling works well.
Interestingly when she was imported all freon was removed with no pressure left in the system. Under that condition no "low freon" code was set in the system at all...
TX '90 ZR1
10-26-2021, 11:13 AM
Matt,
My experience with this is that the AC compressor will not engage when a code 9 is present. This makes your situation curious.
By disconnecting the battery the code will clear and allow the compressor to engage until it picks up the code again.
My suggestion would be to check electrical connections, check AC system pressures and verify correct cycling of compressor.
If blinking light persists after verifying above is correct get into the FSM and follow the troubleshooting steps.
Let us know what you find.
:cheers:
Matt B
10-27-2021, 05:51 PM
Well... As said... Not much to troubleshoot... :dontknow: Everything works as desired, from A/C operation to vent control. No codes set. I entered the HVAC diagnostic mode right after turning on the ignition, right after starting the engine, immediately after the LED started blinking. The error code layer of the menue constantly reports "00" - no codes present. This is really strange. Maybe an error with the HVAC control unit diagnostic mode itself?
When all refrigerant was removed the A/C compressor didn't engage as you said - BUT there was no Code 9. When I refilled the system it immediately started working after a certain refrigerant charge was reached. No battery disconnect needed.
I think I'll observe it for a while to see if it narrows down to a point. Really strange...
TX '90 ZR1
10-28-2021, 05:04 PM
Matt,
Seems really strange to me as well.
If the AC was activated with no pressure I would certainly think that a code should have popped up.
Maybe someone more knowledgeable than me will chime in with some thoughts.
Keep us posted to what happens.
:cheers:
Matt B
10-28-2021, 06:02 PM
I certainly will :). However over here fall has become serious and winter is straight ahead. I don't think my ZR and I will have many dates in a foreseeable time. Usually we have grit salt on the roads from mid November until march or even April. Wish I was in Texas, too...
TX '90 ZR1
10-28-2021, 09:21 PM
Yep, here in Texas the weather allows us to ride our jackrabbits nearly year round!!
16631
Matt B
10-29-2021, 02:29 AM
Hahaha, that's hilarious! I knew that things are just bigger in the states ;)
Matt B
04-19-2023, 04:23 AM
It's been a while since my HVAC came up with some strange behavior and I've monitored it since then. My issues still persist - sometimes the LED flashes (with no noticeable effect) and sometimes the system kinda resets to 75?, full auto mode, rear windshield defrost on.
A/C blows ice cold under any conditions so I don't assume a R134 leak.
When I did the heater core I checked all vacuum lines, actuators and that vacuum routing thing that sits above the drivers footwell. No issues here as well. Everything is tight as a drum.
So... What's next? I don't have any functional issues, it just sucks when it happens. I don't like things that don't work as expected...
Mikey
04-19-2023, 08:43 AM
I occasionally have the same issue. Blinking light but AC always works fine. I have not been able to find exact way to duplicate it. It is random whether it flashes or not.
Matt B
04-19-2023, 03:18 PM
So... It's not a bug, it's a feature? Car with character? Hm, I could be fine with that :D
secondchance
04-19-2023, 09:24 PM
You might have seen this post at CF but just in case.
Take the CC unit inside to a clean well lit place to work on it. There will be 6 ?small? 3/16? bolts that need to come out. One tip I can give you is this - when you've get all 6 removed (two on the back surface, and 4around the perimeter), point the face of the CC unit towards the ground while separating the two halves - you don't want the individual buttons to fall all over the place. With that complete, you will be able to remove the internals. There will be 2 circuit boards joined like a "T". They simply unplug by pulling the two of them apart. Disconnect the small wiring harness and set the larger of the two circuit boards aside.
Holding the control button unit CAREFULLY remove the 4 light bulbs (will look like grey plastic plugs from the back) with a skinny flathead screwdriver - they should take about a 1/4 turn counterclockwise to "unlock." There are two small 3/16? screws in the center of the circuit board holding it to the button holder case, remove them. Lift off the green circuit board and gray rubber contact pad from the buttons. Lay the button holder off to the side. Do not turn it over or the buttons will fall out.
Proceed with cleaning the button contacts on the green board and the gray rubber. All I did was ?lightly? go over the contact circuit points (you'll be able to tell what I'm talking about when you have it apart) with a ?soft? clean pencil eraser, and then give it a good wipe with some Isopropyl Alcohol pads. After it's dry re-assemble and head back to the car, plug it in to the wiring harness for a test - it should work as new!
Entire thread is;
https://www.corvetteforum.com/forums/c4-general-discussion/1519199-climate-control-button-repair.html
Thread suggests blinking could be due to film build up on control contacts and that a cleaning fixed occasional blinking of ?auto? button.
DRM500RUBYZR-1
04-20-2023, 07:27 AM
Yep, here in Texas the weather allows us to ride our jackrabbits nearly year round!!
16631
:)
:thumbsup:
:cheers:
Marty
DRM500RUBYZR-1
04-20-2023, 07:32 AM
You might have seen this post at CF but just in case.
Take the CC unit inside to a clean well lit place to work on it. There will be 6 ?small? 3/16? bolts that need to come out. One tip I can give you is this - when you've get all 6 removed (two on the back surface, and 4around the perimeter), point the face of the CC unit towards the ground while separating the two halves - you don't want the individual buttons to fall all over the place. With that complete, you will be able to remove the internals. There will be 2 circuit boards joined like a "T". They simply unplug by pulling the two of them apart. Disconnect the small wiring harness and set the larger of the two circuit boards aside.
Holding the control button unit CAREFULLY remove the 4 light bulbs (will look like grey plastic plugs from the back) with a skinny flathead screwdriver - they should take about a 1/4 turn counterclockwise to "unlock." There are two small 3/16? screws in the center of the circuit board holding it to the button holder case, remove them. Lift off the green circuit board and gray rubber contact pad from the buttons. Lay the button holder off to the side. Do not turn it over or the buttons will fall out.
Proceed with cleaning the button contacts on the green board and the gray rubber. All I did was ?lightly? go over the contact circuit points (you'll be able to tell what I'm talking about when you have it apart) with a ?soft? clean pencil eraser, and then give it a good wipe with some Isopropyl Alcohol pads. After it's dry re-assemble and head back to the car, plug it in to the wiring harness for a test - it should work as new!
Entire thread is;
https://www.corvetteforum.com/forums/c4-general-discussion/1519199-climate-control-button-repair.html
Thread suggests blinking could be due to film build up on control contacts and that a cleaning fixed occasional blinking of ?auto? button.
Correct!!!
or remove and send to Batee if you fear fumbling with the internals.
:thumbsup:
:cheers:
Marty
dredgeguy
04-20-2023, 06:38 PM
Hi Matt, after reading your posts, I had the same problem today. Mine started blinking for about 30 seconds and then went solid green, no problem with the AC during blinking or solid. That was true for about 15 minutes until I got to the gas station. After filling up no AC. Light did not blink at all, solid green but no joy. Bummer, had it serviced last fall but looks like must have a leak or a bigger problem.
Starman
05-01-2023, 08:47 PM
So about 14 years ago my HVAC was going nuts periodically and resetting to 75 degrees (default temp). Very annoying as it slowly cycles the mix door from end to end as part of the reset and either cooks or freezes you depending on outside temp. The HVAC controller has the same crappy capacitors as the Bose amps. I took the controller apart, replaced the caps and resoldered some connections that looked dull. Has worked perfectly since. Beware there is a fastener for the dash face in the vent above it.
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