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01' STS blower not working


larrylee

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Hello all, I have an 01' STS that has an intermittant no blower condition. AC display shows fan speed, AC cycles and lines under hood are cold. No air from vents hot or cold. I removed ground from frame under hood and cleaned/reattached. Also checked voltage at plug to blower motor. Red and Black show continuity to ground, Yellow has 14.5v (seems high to me) and 8.5volts on the Lite Green. Any ideas on what else to check? The blower DOES work intermittantly. Thanks, Larry.

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There might be a clue or hint stored in your onboard diagnostic system as a DTC (Diagnostic Trouble Code).

Here is how to display DTCs on your car.....

http://www.caddyinfo.com/readingcodes.html

Thanks, Jim. I'll pull the codes after work and post them up. I didn't think an issue like this would store any codes because it doesn't affect driveability. Unless of course you consider the dirty looks I get when the wife gets home on a hot day with no AC in her car a driveability issue...hahaha. Larry

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OK, I pulled the codes. No current codes, only

DIM B1324 History

IPC u1016 History

The fan in the center console for the rear seat passengers works even if the dash vents aren't if that helps...

Thanks, Larry

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B1324 - A/C Refrigerant Overpressure

Not sure how that code relates to your HVAC blower situation, but it might(?). There is quite a bit of fail-safe engineering integrated into the various vehicle systems.

Can you duplicate the problem with the HVAC controls in a manual non-A/C mode?

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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B1324 - A/C Refrigerant Overpressure

Not sure how that code relates to your HVAC blower situation, but it might(?). There is quite a bit of fail-safe engineering integrated into the various vehicle systems.

Can you duplicate the problem with the HVAC controls in a manual non-A/C mode?

Nope. Sometimes it blows, sometimes it doesn't...Doesn't seem to matter if A/C is on or off. Rear fan works in either mode just fine. Does the blower go out intermittantly or all at once? I'm not against buying a new one but I'd like to be confident that I'm not throwing good money after bad. It is housed in the unit mounted on the passenger side firewall in the engine compartment, right? That's the plug that I took the voltage readings from. I had power there when the fan was not working...I also noticed that the unit is isolation mounted but I saw grounds in the plug. Hmmmmm...

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Here is how I would tackle your situation if it was my car.

The power source for the front seat HVAC blower motor is a 30A fuse in the (under) rear seat fuse block identified as HVAC BLO. Be sure the fuse blades are corrosion free.

Motor speed is controlled by the Blower Control Module using PWM on the blower motor chassis ground return line, pin "B" (black wire). If you can read battery voltage on pin "A" (purple wire) of the blower motor chassis connector, that would be a good sign.

When the HVAC is set to a manual mode (not AUTO), the motor speed can be selected with the toggle on the HVAC panel.

When the HVAC is set to AUTO, another module and many more sensors are in play.

If you can control motor speed in one of the "manual" HVAC modes, I would call the blower motor and the Blower Control Module "good".

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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Here is how I would tackle your situation if it was my car.

The power source for the front seat HVAC blower motor is a 30A fuse in the (under) rear seat fuse block identified as HVAC BLO. Be sure the fuse blades are corrosion free.

Motor speed is controlled by the Blower Control Module using PWM on the blower motor chassis ground return line, pin "B" (black wire). If you can read battery voltage on pin "A" (purple wire) of the blower motor chassis connector, that would be a good sign.

When the HVAC is set to a manual mode (not AUTO), the motor speed can be selected with the toggle on the HVAC panel.

When the HVAC is set to AUTO, another module and many more sensors are in play.

If you can control motor speed in one of the "manual" HVAC modes, I would call the blower motor and the Blower Control Module "good".

With blower fan speed on high, auto off,

14v on white

8.5v on lt green

0v no grd on purple

grd on red and black

30a fuse in rear looks good

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Don't touch the purple wire. It's the network data link.

CTS-V_LateralGs_6-2018_tiny.jpg
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It is housed in the unit mounted on the passenger side firewall in the engine compartment, right? That's the plug that I took the voltage readings from. I had power there when the fan was not working...I also noticed that the unit is isolation mounted but I saw grounds in the plug. Hmmmmm...

Ok, I'm feeling stupid now...That must be the wiper motor. I believe I found the blower under the dash in the passenger side footwell.. :rolleyes: It has a plug that has a purple, black and bare stranded wire I'm assuming is a ground. I started the car this morning and the blower works fine in auto and manual mode. Does anyone know if the black wire is the power to the fan. If that's the case then it would be safe to say that if I have no power there when this thing quits again, the fan itself is not the problem? Is the fan housing removable without digging too far into the dash? I can see about 5 little gold bolts holding the housing on, any surprises under there? Thanks for any info, Larry.

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Power is provided via the purple wire (see post #7).

Fan speed is determined by the control module connecting the black wire to ground via PWM.

You should see 12 Volts between the purple wire and the bare (non-insulated) bonding wire.

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

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  • 3 years later...

I found on my 03 sts there are a group on ground wires located under the rt sid door threshold at forward end, the ground pin for the blower motor is in a large group off ground wires at one common ground point, i needed to take apart to find this problem, it had gotten so hot it melted the metal to plastic connection causing the motor to be intermitant, crazy thing it wound sometimes start working when someone in the passenger front seat would slam the door closed!!! go figure.

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