A/C troubles

[Batmobile]

So happy with everyone's input on the forum, thanks fellas. Figured I run this through you guys as well, as it has me scratching my head. Any help would be so much appreciated. It gets to 47 degrees Celsius over here and it really is a Sauna with a Supercharger on it.

Here's the situation:
The outside temperature sensor is not giving a correct reading. So I replaced part #10248414, which was the ambient air temperature sensor located next to the horns on the left side in front of the radiator. The sensor still gave erratic readings.
I am looking on the touch screen, and see it pointing to 24C, which is far from the truth since it's +40C outside.

I kick on the A/C and set it to 16C, go about my way and watch the outside temp readings. Since it seems like the compressor will only kick in if it's really hot outside, so there's a calculation happening there based on the readings of this ambient air sensor.
When it's reading +30C outside, the compressor kicks in and I get nice cool air. But the sensor might suddenly drop and read NEGATIVE 40C! (-40C) so the "ICE POSSIBLE" warning appears on the dash. Basically start getting very hot air from the vents, even though I have A/C on with temp set to 16C. My assumption is it's referencing the outside air temp and trying to regulate cabin temp UP to 16C, therefore shutting off the compressor and blasting hot air.


Ok, since the sensor itself was not the issue, I threw on the Tech2 and found the following issues.



So there's an issue with the circuit, apparently. I also realized, the two horns are on the same harness, and I think my high note horn is not working. (whichever the one is to the back is, not working). The real question is, what and how do I go about fixing this?
I already have the front bumper and headlights off, but am not an electric guru so don't know where to start.



ِAny pointers?

 

[Hudson River Steve]

I would trace the ground wires for the temp sensor and horn circuits all the way back to the chassis. . Probably just need to clean the spots where the grounds attach to the chassis.

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[Batmobile]

Can someone please help me narrow down ground circuits involved with the outside air temperature sensor?

It is now constantly reading 75F, or 24C all the time!!

Therefore not cooling when the actual outside temp is 43C!!!


I would appreciate any input on this as I can't find where the issue is. However, still getting the B0159 error when I scan with the Tech2.

 

[Batmobile]

While looking at the horn harness to make sure the 10mm bolt had clean contact to ground, I realized that my skid plate must've been hit before by the previous owner. I can see cracked joints where it is actually held to the chassis (underneath and surrounding the main radiator).
Now the real question is, are these contact points for ground?





This high note horn connector is loose, and will work when I move the cable. A tech looked at it and told me it was a bad horn, as these are the symptoms bad horns give, don't know if that's true.

 

[Batmobile]

An update:

So I took the car to a reputable corvette technician. They were able to get the outside ambient air temperature sensor to read correctly, finally. They used a jumper in the main fuse box so that the HVAC gets a direct signal from the sensor upfront. This was the only way the sensor started reading correct outside temps.

However, there still seems to be an issue with the A/C, as it's not always cold. If I accelerate or stress the car even for 10 secs, the A/C stops blowing cold air. The only remedy is to switch off the car completely, open and close the door and the AC would kick back in with cold air. <-- this doesn't always work either. Sometimes the AC will just not blow cold air.

The techs also inspected the low and high pressure lines and fully replaced the freon - with no solution.
Appreciate your feedback on how this issue can be traced to the root

 

[Hudson River Steve]

So the problem with the ambient air sensor was a wiring issue.

How do they know that there aren't more wiring issues affecting your a/c system?

Did the dealer tech drive the car with a Tech2 connected while monitoring the a/c system?,

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[long Tall Sally]

I really think you have other problems. Like I told you , I disconnected my outside temp unit and the ac worked fine did not miss a beat and its 99 here. I really do not see in the manual or wiring diagram where the temp sending unit controls the inside air. My gauge without a unit showed the default temp and did not change . Plugged it back up temp reads correctly and a/c still works just like it did unplugged. I have an 08 non v so maybe the v does something differently but I doubt it.

 

[Batmobile]

Correct, the wiring was culprit and now the sensor works fine.

The AC still only cooling properly when the RPM's go above 2k, which seems to point to a bad compressor. New compressor around $400?

 

[long Tall Sally]

that also is a symptom of a clogged dryer or expansion valve. While he had the system evacuated did he clean the dryer. I always back flush the dryer with nitrogen and usually replace the orifice tube. That will tell you if the compressor is starting to go if there is any metal in the system. Also look to see as I don't know if the v has a a/c shut down connected to the throttle. Most BMW and Mercedes will cut off the a/c compressor under full throttle. I see one valve listed for the a/c that is specific to the v so that may be bad. can you see that your compressor is engaged under 2000 rpms? what temp is the air coming out your vents at idle? vs at 2000 rpms?

 

[Batmobile]

that also is a symptom of a clogged dryer or expansion valve. While he had the system evacuated did he clean the dryer. I always back flush the dryer with nitrogen and usually replace the orifice tube. That will tell you if the compressor is starting to go if there is any metal in the system. Also look to see as I don't know if the v has a a/c shut down connected to the throttle. Most BMW and Mercedes will cut off the a/c compressor under full throttle. I see one valve listed for the a/c that is specific to the v so that may be bad. can you see that your compressor is engaged under 2000 rpms? what temp is the air coming out your vents at idle? vs at 2000 rpms?

Hey LTS!
Had to put this on the back burner and use my Mercedes for the time being.

However, the issue is still a malfunctioning A/C. It seems that any pressure put on the engine would cut off the compressor from sending cold air. I'm not sure if this had to do with directly linking the ambient outside temp to the fuse ox so it can read outside temps correctly. I also had all engine belts replaced at the same time, I'm wondering if it's a tightening issue to get the A/C compressor running normally under idle.

To your suggestion, LTS, I had an A/C shop check the whole system and they think it's fine - however maybe the compressor is starting to go bad.

Should I bite the bullet and just go for a new A/C compressor?