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Bad Ground Wires - Incorrect Temperature Display in DIC
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simopala
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PostPosted: Sun Jul 11, 2010 12:20 pm    Post subject: Snif ! Bad Ground Wires - Incorrect Temperature Display in DIC Reply with quote

The temperature displayed on the DIC is way too low which leads me to believe that the sensor is not properly grounded. A further consequence is that the air conditioning is not as effective?

My question is;
Where are all the ground connections physically located?
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k6ng6r00
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PostPosted: Mon Jul 12, 2010 11:58 pm    Post subject:   Reply with quote

mine isnt right either but idk if its because of the temperature sensor being grounded wrong, how do you figure that?

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PostPosted: Tue Jul 13, 2010 12:09 am    Post subject:   Reply with quote

FWIW: I don't think there is any way the air conditioned would be less effective if the ambient temp sensor isn't working properly. They are likely to be two discrete problems.

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simopala
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PostPosted: Tue Jul 13, 2010 12:30 am    Post subject:   Reply with quote

I think the A/C problem is the A/C insufficient refrigerant
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Bill58
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PostPosted: Tue Jul 13, 2010 1:56 am    Post subject: Snif ! Re: Bad Ground Wires - Incorrect Temperature Display in DIC Reply with quote

simopala wrote:
A further consequence is that the air conditioning is not as effective?

This is from the '05 owners manual.

"It should be noted, that the air conditioning compressor
will be engaged unless the outside temperature is
40F (4C) or below."

The sensor is behind the grill attached to the core support. I would follow the wires from there.
Good idea to check freon pressure also.
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PostPosted: Tue Jul 13, 2010 9:49 am    Post subject:   Reply with quote

Thanks!
One time I get 62F, the next time, later in the day i get 20F - It's 80+F outside
So that makes perfect sense - 20F outside equals no demand for A/C!!
Also I noted that colder air on one side compared to the other side - So I guess the sensors in the air ducts?

My other issue is a noisy compressor which is due to low refrigerant or compressor on the way out?
Thanks for all your help guys!
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PostPosted: Wed Jul 14, 2010 8:44 am    Post subject:   Reply with quote

The ambient temp sensor behind the grill has no bearing on the A/C...

In fact, if you don't have the DIC, there is no ambient temp sensor there at all..

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PostPosted: Wed Jul 14, 2010 11:14 am    Post subject:   Reply with quote

Last year, my 00 LS had the a/c compressor running full time when the switch was on. Normally, the compressor cycles on and off, but mine just stayed on. I had more cold air than I could take, on a 95 degree day with 85% humidity I had the fan on low and was frozen after just 10 miles. It turned out to be 1/2 lb low. They told me that 00 was an odd year in that normally the a/c gets less efficient as the refridg level drops, but the 00's compressor will run all the time. Just started doing the same thing again last week, along with a noisy compressor so I'll know later today what the result is.
The OP might want to listen and see if the compressor is cycling, if not, you're likely low on freon.
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PostPosted: Wed Jul 14, 2010 12:02 pm    Post subject:   Reply with quote

bbengineer wrote:
The ambient temp sensor behind the grill has no bearing on the A/C...

In fact, if you don't have the DIC, there is no ambient temp sensor there at all..

BBEngineer


Just for giggles I sprayed caned air (inverted) on the sensor. Went to 23F, compressor clutch would not engage, the light on the control blinked when pushed. As the temp came up past +40F the clutch engaged. That sensor dose control the a/c. Before you call bull$hit, try it.
I also have a 97 GP with the pigtail but no sensor so I know what you are saying. Darn if I know how that one works.
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PostPosted: Wed Jul 14, 2010 12:19 pm    Post subject:   Reply with quote

Kinda difficult to try it when I don't have an Impala...

And since the ambient sensor is wired directly to the DIC, I don't see how the HVAC could use it... much less rely on it when it's an option and the vast majority of Impalas don't have it

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EDIT: And here is how it is done... by physics. When ambient temperature is low (below 40deg or so), the low side pressure sensor will prevent the compressor from turning on because the ambient temp causes the freon pressure to drop below the pressure turn on threshold...

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PostPosted: Wed Jul 14, 2010 12:33 pm    Post subject:   Reply with quote

When the temp gets in the low 30s the DIC displays Ice possible drive with care. There is some logic driving the display. Im just sayen. I have empirical data, I cooled the sensor.


Last edited by Bill58 on Wed Jul 14, 2010 6:29 pm; edited 1 time in total
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PostPosted: Wed Jul 14, 2010 12:40 pm    Post subject:   Reply with quote

Bill58 wrote:
When the temp gets in the low 30s the DIC displays Ice possible drive with care. There is some logic driving the display. Im just sayen. I have impirical data, I cooled the sensor.


The logic is completely within the DIC... you have one data point... and that data point doesn't account for the hundreds of thousands of Impalas without the DIC

Not to mention, he said his AC was less effective, not non-functional

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PostPosted: Wed Jul 14, 2010 12:45 pm    Post subject:   Reply with quote

I think this has crossed to Bad Form on my part. Try cooling the sensor if you get a chance, but Im going to let it go. Nice give n take.
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PostPosted: Wed Jul 14, 2010 12:55 pm    Post subject:   Reply with quote

I finally found it burried in the service manual:

Quote:

The PCM will enable the A/C compressor clutch whenever the engine is running and the A/C has been requested unless one or more of the following conditions are present:

* Throttle angle is more than 96 percent.
* A/C head pressure is more than 440 psi (4.6 volts) or less than 32 psi (0.3 volt) as determined by the A/C refrigerant pressure sensor.
* Ignition voltage is less than 10 volt
* Engine speed is more than 4400 RPM for any amount of time.
* ECT is more than 124C (255F).
* IAT is less than 5C (41F).


It uses the iAT to determine the exterior temperature...

I guess it's possible that it may factor in the Ambient Temp from the DIC if equipped, but i would be extremely surprised

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PostPosted: Wed Jul 14, 2010 1:08 pm    Post subject:   Reply with quote

On a semi-related note, if there a complete A/C troubleshooting article somewhere on the forum? I haven't come across anything in my travels, but my A/C stopped working more than 2 years ago, and this summer is HOT.

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Last edited by Lingenfelter on Wed Jul 14, 2010 1:08 pm; edited 1 time in total
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