AC/fan not working no codes showing

[olymacs]

Hope this posts ok since I am new. I have 90 C4 and the AC/fan does not work and when up and down arrows are pushed and then auto no codes are shown. Fuse looks ok so not sure what to check next. Any ideas or suggestions appreciated. It is the automatic system.

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[ecss]

Hope this posts ok since I am new. I have 90 C4 and the AC/fan does not work and when up and down arrows are pushed and then auto no codes are shown. Fuse looks ok so not sure what to check next. Any ideas or suggestions appreciated. It is the automatic system.

Sent from my SCH-I545 using Tapatalk

If you're talking about the blower motor fan here's how to trouble shoot it.

There are no codes for a bad fan motor.

The fan motor is powered by the blower control module which is located under the hood passenger side
inside the evaporator housing.

You need a volt meter to test the circuit.
Look at the top of the evaporator housing. There are two electrical connectors.
Turn the ignition On.
Press one of the buttons on the bottom row to turn the HVAC system On.
Press the up arrow fan button on the HVAC control head until 10 appears in the LCD.

Red meter probe on Red wire.
Black meter probe on Black wire which is ground.
Should measure 12 volts. This is the power source for the module and comes from a fusible link.

Red meter probe on the Purple wire.
Black meter probe on the Black wire.
Should read around 12 volts.
If you measure 12 volts the blower motor should run.
If the blower motor doesn't run the blower motor is bad.

If no 12 volts move the Red probe to the Dark Green/Yellow wire.
Keep Black probe on Black wire.
Should measure around 6-7 volts DC.
If you do the Blower Motor control module is bad.

Remove a couple of small bolts and and lift the blower control module out of the evaporator housing.
Do not unplug the two electrical plugs until you pull the module up and out of the housing because
the module will drop into the housing. :eyerole

Here's what the blower control module looks like.

 

[olymacs]

Thanks, i will give it a try. Only problem I have is the screen never seems to show anything.

 

[ecss]

Thanks, i will give it a try. Only problem I have is the screen never seems to show anything.

In your first post you said you pressed the arrow keys to get into diagnostic mode and then pressed the
auto button and saw no codes? :confused

Now you say the LCD is blank?

You need to verify the CTSY fuse is good. It's has 12 volts all the time.
You need to verify the AC fuse is good. It's 12 volts when the ignition switch is in Run.

Those are the only two fuses used by the HVAC system.

When you turn the ignition On. The HVAC control head should display the outside temperature
in the LCD.

Are you saying the LCD is blank?
Is there any back lighting for the LCD?
Does the LCD show ---- which indicates it's not communicating with the HVAC Programmer which is the
brains for the system and is a black rectangular box bolted to the firewall to the right side of the gas pedal.

 

[olymacs]

Thanks, it was the CTSY fuse. Now the screen is lite. But it shows only 00 meaning all is ok but it does not blow any cold air. Thanks again for getting me pointed in the right direction.

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[ecss]

Thanks, it was the CTSY fuse. Now the screen is lite. But it shows only 00 meaning all is ok but it does not blow any cold air. Thanks again for getting me pointed in the right direction.

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Does hot air blow out of the vents?:ugh

 

[olymacs]

Yes,

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[ecss]

Yes,

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If you press the temperature rocker switch to the left does the temperature display in the LCD decrease and eventually go to 60F?

Start the engine.

Then press the AC button. Does the green LED button below the AC button come On?

You should hear a click sound which is the compressor clutch engaging. The engine idle speed should increase
to compensate for the compressor turning on.

If the AC compressor clutch is not engaging you're probably low on freon.

With the engine off.
Take a tire pressure gauge and measure the pressure at the accumulator port.
There may be a black cap you need to remove.
Verify the pressure is above 50 psi.
Post what pressure you read.
If it's not above at least 50 psi you have a leak in the system and need to get that fixed.

Here's a picture of what the accumulator looks like. The arrow points to the schrader
valve where you can measure the pressure.

 

[olymacs]

Thanks again, I think we have it now. Now on to the radio.

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