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I have a 2007 impala lt 3.9 engine. I am getting a code

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I have a 2007 impala...
I have a 2007 impala lt 3.9 engine. I am getting a code P0645 and my ac compressor is constantly running even when it is aupposed to be off.
Submitted: 2 years ago.Category: Chevy
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Answered in 8 minutes by:
2/24/2016
Chevy Mechanic: Don - Mo Lurch, Auto Mech / Electronics replied 2 years ago
Don - Mo Lurch
Don - Mo Lurch, Auto Mech / Electronics
Category: Chevy
Satisfied Customers: 21,464
Experience: Chevrolet Cert., Heavy Line Mech, Race Shop Owner, Mobile Electronics.
Verified

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sorry for the delay............
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Greetings...... “Hi, I’m Don (aka MOLurch) and I look forward to helping you!”
.

This is typically caused from a bad compressor clutch relay, bad connections to it or bad PCM
Ignition voltage is supplied directly to the A/C compressor clutch relay. The powertrain control module (PCM) controls the relay by grounding the control circuit through an internal solid state device called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line, which is monitored by the PCM. When the PCM is commanding a component ON, the voltage of the control circuit should be near 0 volts . When the PCM is commanding the control circuit to a component OFF, the voltage potential of the circuit should be near battery voltage.
The Relay is located in the Under Hood Fuse / Relay Box
I can post the Testing Procedures if you want, but you will need use of GM Scan Tool or Equal
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Customer reply replied 2 years ago

I have a scan tool. Like the one on the link. Will it work? It does read 3 different ac things.

http://www.amazon.com/Launch-Creader-Reader-Automotive-Function/dp/B00EN7JPIO

Chevy Mechanic: Don - Mo Lurch, Auto Mech / Electronics replied 2 years ago

according to specs, this will not......
But you can try a reset of the Trouble Codes & see if that clears the issue.

.

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Customer reply replied 2 years ago

I have tried that. And also disconnecting the battery.

Chevy Mechanic: Don - Mo Lurch, Auto Mech / Electronics replied 2 years ago

ok...........

as stated, "typically caused from a bad compressor clutch relay, bad connections to it or bad PCM"
Replace the Relay, clear the codes & try
Otherwise, you will need to Test via correct type Scan Tool

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Customer reply replied 2 years ago

My scanner shows ac relay circuit short to ground. I know the relay is good cause I swapped it with another relay. I would like to test the pin holes for the realy...can u tell me if im supposed to have power or ground to each pin hole.

Chevy Mechanic: Don - Mo Lurch, Auto Mech / Electronics replied 2 years ago

Here is GM Test procedures:
click attachment below

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The numbers below refer to the step numbers on the diagnostic table.

3.Listen for an audible click when the A/C compressor clutch relay operates. Command both the ON and OFF states. Repeat the commands, as necessary.
4.This step tests for voltage at the coil side of the A/C compressor clutch relay. The 10-amp fuse supplies power to the coil side of the A/C compressor clutch relay.
5.This step verifies that the PCM is providing ground to the A/C compressor clutch relay.
6.This step tests if ground is constantly being applied to the A/C compressor clutch relay.
7.This step tests for a short to voltage or an open.
13.Perform the programming procedure for the PCM.

.

Please do the right thing and leave a rating, using the rating system, so I may be credited for this Q&A.
.
NOTE: Do NOT Rate on how much TIME you waited, because I am not on 24 / 7 and I answer as soon as I see the question.
The question will still remain open for follow up questions if needed.
.
If for any reason, you can't rate my answer OKAY, GOOD, or EXCELLENT today.
Please reply and let me know why, so I can help more/better.
.
Rating is very Important to our Service
.

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Chevy Mechanic: Don - Mo Lurch, Auto Mech / Electronics replied 2 years ago

.
Hello again Lurch here.

I noticed we have not yet resolved your concern you asked about.

If I have helped, please RATE my answer

I would appreciate it if you would reply so I can offer my skills and knowledge and repair guide access to help as best I can.

If you have already rated my answer, then Thanks alot.

If you have new questions now or in the future please do not hesitate to ask them.

If you would like me to assist you. Just bookmark this page so you can access my profile easy and post a new question from the question box on my profile page.
.
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