Passengers A piller base

 

OK, since it is accessible, I'll clean it up first and hope to get lucky......
Best,
W.

 

No luck here. I cleaned it up and have bare metal to metal on G202. Same low voltages. Bummer.

Next check: fuse voltage. Another newbie question: Where is the Instrument Panel Electrical Center?

Tks,

 

Passengers foot well:

 

ttt

 

Hi Bill,
Coupla questions, pls:
When I disconnect the ambient sensor harness wire from the sensor, the indication on the AC Dual Climate Control unit does not change. It is now stuck at 12F. Am I correct that this means the problem is inside the control unit?

The July 2010 issue of Vette magazince has an article by James Miles that focuses on replacing the small bulbs on the printed circuit board in the DCC unit. In the article, he mentions re soldering the 241 resistors. Are these the ones that you have resolderd in the units that you have repaired?

Thanks.

 

Hi Bill,
I'm about to pull the DCC head unit and open it up. Where should I look for poor solder connections?
Thanks.

 

DCC ?????? Whats a DCC

 

Dual Climate Control HVAC head unit.
W.

 

OK. The resistors that commonly come loose effect illumination but,,,,thats not to say other ones wont have a bad solder joint. Look at the connector and find the exact circuit and follow that trace. Im positive you will find sme second rate solder job. I hate DELPHI!

BC

 

Hi Bull,
I'm exhausted on the AC problem on the 99. I cannot find anything to fix the erratic EXT TEMP reading which prevents the AC from working as it should. Here's what I've checked so far:

1. Erratic reading occurs in AUTO or Man function. Low reading prevents AC ops in either position.
2. Changed sensor - no change
3. Changed sensor connector on harness - no change
4. Checked grounds G101, G102, G104 and G202. Connectors were opened and cleaned with steel wool. Frame was scraped clean and ground connector bolted down again.
5. Checked ground from sensor connector to ground = .5 ohms
6. Checked voltage green black wire at sensor connector to ground = 3.5VDC
7. Check voltage at fuse 27 under dash - 12VDC+ with engine running
8. Checked ground from pin D1 on connector that connects to back of HVAC head unit = 1 ohm
9. Checked voltage from pin D3 on connector that connects to back of HVAC head unit = 6VDC
10. Temp installed new GM HVAC head unit - no change.
11. Replaced battery - no change
12. Checked Diagnostic Codes - no HVAC code shows

I'm hoping that there's something else - my HVAC head unit is now stuck at -14F!

 

Those ground readings should be lower than that. Lets try this:

Unplug the sensor from the connector and Temporarily install the the sensor at the connector on HVAC unit and see if that changes things. My guess would have been the head unit is bad but you resolved that issue.

My guess is that the harness between the HVAC head unit and the sensor is giving you the problems.

Bill

 

Hi Bill,
I failed to list that I had checked the continuity of the harness. The green/black wire tested 1 ohm from end to end. The black wire tested .5 ohm to ground.

Anything else I can check?

Will

 

Back probe the HVAC connector and wire in the temp sensor directly to the HVAC head. That will eliminate a LOT of connections and grounds.

BC

 

Hi Bill,
If the end to end test of the green/black wire is less than 1 ohm, doesn't that mean that all the intervening connections are good?

Stumped.....

 

What does your meter read when the meter leads are shorted? That wiring run is fairly short. Should not read that high although 1 ohm isnt all that much.

Im just trying to eliminate all the stuff that I can and try to find easy ways to do it. If you phisicaly plugged the sensor in the back of the HVAC unit and it still reads the same, the harness isnt the issue.

Sitting here writing this, gave me another idea. Read the sensor with an ohm meter and make sure it tracks properly.

The outside air temperature sensor is located in the RH front of the engine compartment, on the radiator support near the horn assembly. In this position, it is exposed to airflow before the air enters the radiator. This provides a sample of the outside (ambient) air temperature.

The sensor is a thermistor used to control the signal voltage at the HVAC Control Assembly. The HVAC Control Assembly supplies a reference voltage (about 5 volts) on CKT 735 to the sensor and measures the voltage drop in the circuit to obtain a temperature signal. This signal is an input that tells the HVAC control head how much cooling or heating will be required to deliver to the passenger compartment. It also affects the mode and blower motor speed.

Resistance of the sensor varies from 242,700 ohms at -40°C (-40°F) to 2488 ohms at 60°C (140°F). When the outside (ambient) air temperature is cold, the thermistor resistance is high; therefore, the HVAC Control Assembly will receive a high signal voltage input. If the air temperature is hot, the thermistor resistance is low, the HVAC control head will receive a low signal voltage input.

The outside temperature is displayed on the display panel of the HVAC Control Assembly. The displayed temperature value is derived from a series of calculations performed by a processor in the HVAC Control Assembly. The calculations performed by the HVAC Control Assembly will use coolant temperature, vehicle speed, and ignition ON/OFF time to limit how fast the temperature display will be increased if a difference exists between the outside temperature sensor reading and the last value calculated by the HVAC Control Assembly for the temperature display. These calculations are used to eliminate any heat soak variations which may occur around the outside temperature sensor particularly after the engine has been turned off. If the car has been turned off for over 3 hours and then is restarted, the temperature display is immediately reset to ambient temperature conditions. If the car has been restarted within a 3 hour period after shutdown, the temperature display will not immediately reset. The temperature display will update after the car is driven between 32 and 72 km/h (20 and 45 MPH) for 90 seconds or above 72 km/h (45 MPH) for 60 seconds. In either condition, the temperature display will then be allowed to increase at the rate of 1.3 degrees Fahrenheit per second. Update rates are quicker at higher speeds because the outside temperature sensor reaches ambient temperature faster. If vehicle speed is not available from the Class II data line, it will be assumed to be at 40 km/h (25 MPH). Finally, if coolant temperature is within 40°C (104°F) from the outside temperature sensor reading, the temperature display will update immediately upon vehicle start up. If the above conditions are not met, then the outside temperature display will not be allowed to increase.

A condition may exist were the outside temperature sensor is reading a lower temperature then the last calculated value stored in the HVAC control head. In this condition, the temperature display will always be allowed to decrease at a rate of 1.3 degrees Fahrenheit per second. Heat soak conditions in the engine compartment will not exist and thus do not cause a false lower temperature reading by the outside temperature sensor.

If the outside temperature sensor is shorted or not connected, the system will always read 13°C (56°F) as a default.

Conditions for Setting the DTC
With the ignition in the ON position, CKT 735 is checked continuously.
CKT 735 stays at or near zero voltage.
Action Taken When the DTC Sets
The HVAC Control Assembly displays the outside temperature as 13°C (56°F).
The HVAC Control Assembly stores a DTC B0332 in memory.
Conditions for Clearing the DTC
Using the IPC clearing feature.
Using a scan tool.
A history DTC will clear after 50 consecutive ignition cycles if the conditions for the fault is no longer present.
Diagnostic Aids
If the DTC is a history or an intermittent. Try to perform the tests shown while "wiggling" wiring and connectors, this can often cause the malfunction to appear.
Visually inspect sensor connector and harness for damage, corrosion or water intrusion.
Check for adequate terminal tension, mis-routed harness, rubbed through wire insulation, and broken wire inside insulation.
The resistance value of the sensor must be close to the values given in the chart. If not the sensor is considered skewed and must be replaced.
°C
°F
Ohmsohms

Temperature vs. Resistance Values (Approximate)

-40
-40
242,700

-30
-22
177,000

-20
-4
97,060

-10
14
55,319

0
32
32,654

10
50
19,903

20
68
12,493

30
86
8,056

40
104
5,327

50
122
3,603

60
140
2,488


Test Description
The numbers below refer to the step numbers on the diagnostic table:

This test checks for the 5 volt reference signal being sent from the HVAC Control Assembly along CKT 735.

Checking for a short to ground in CKT 735.

Replace the ambient outside temperature sensor.

Erase all DTCs and recheck for repair verification.

Repair a short to ground in CKT 735.

Replace the HVAC Control Assembly.

DTC B0332 - Outside Air Temp Sensor Short To Ground (CJ2) Step
Action
Value(s)
Yes
No

1
Were you sent here from the HVAC System Check (CJ2)?
--
Go to Step 2
Go to HVAC System Check

2
Disconnect the ambient outside temperature sensor connector.
Turn the ignition switch to the ON position.
Use a DMM to measure the voltage between terminal A of the ambient outside temperature sensor connector and ground.
Is the voltage within the specified values?
4.0-6.0V
Go to Step 4
Go to Step 3

3
Turn the ignition switch to the OFF position.
Disconnect the HVAC Control Assembly connector.
Using a DMM measure the resistance to ground of circuit 735 from the HVAC Control Assembly connector terminal D3 to ground.
Is the resistance within specified values?
Infinite
Go to Step 7
Go to Step 6

4
Replace the ambient outside temperature sensor.

Refer to Ambient Temperature Sensor Replacement .

Is the replacement complete?
--
Go to Step 5
--

5
Using a scan tool, clear all DTCs stored in memory.

Refer to Diagnostic Trouble Code (DTC) Clearing .

Do all DTCs erase from memory?
--
Go to HVAC System Check
Go to appropriate DTC table for diagnosis

6
Locate and repair a short to ground in CKT 735.

Is the repair complete?
--
Go to Step 5
--

7
Replace the HVAC Control Assembly.

Refer to Control Assembly Replacement .

Is the replacement complete?
--
Go to Step 5
--



--------------------------------------------------------------------------------
Document ID# 376659
1999 Chevrolet/Geo Corvette

 

Bill, thanks again for your posts. My Z06 is running perfect since I followed your advice on fixing my ignition switch problem.

 

Hi Bill,
My meter reads 0 ohms when the leads are shorted.

I'll do the sensor resistance checks on both the old and new sensor and report back.

Your excellent write up states, "If the outside temperature sensor is shorted or not connected, the system will always read 13°C (56°F) as a default." What does it mean if the sensor is removed and the reading is something other than 56F?

Thanks again.

 

Hi Bill
Sensor resistance checks indicate normal operation.
Now what?

Stumped...

 

Hi Bill,
A professional Corvette mechanic with over 20 yrs experience making a living working on primarily C5s and C6s came over tonight to verify my tests. They all checked out as previously reported.

He thinks there may be some sort of reset that needs to take place after sensor replacement or battery replacement or control head replacement.

Any ideas appreciated.

Tks.