Jump to content
CaddyInfo Cadillac Forum

Recommended Posts

First time Cadillac owner. Received pristine 03 Seville SLS 50,000 well cared for miles. Heater blower motor quit. Checked all related fuses. I searched the internet to find out what the problem was. I have the auto heating system upgrade, so it doesn't have a resister or a relay, it has a blower motor control module that is connected to the side of the blower motor plenum. I check it as good as I could without a diagram and concluded the module was bad. I replaced the module with no success. From what I understand there are 3 wires going into the module, then into the blower motor. A colored, a black and a bare wire. The colored is the hot, black is the ground. The hot and the ground are always present. The bare wire supposedly sends a square wave pulse to the motor that actually controls the motor and speed. I don't want to spend all my money on parts I don't need. If anybody can give me info on trouble shooting the system, my wife would really appreciate it.

Link to comment
Share on other sites


....Heater blower motor quit. Checked all related fuses.

Is that the front seat blower motor?

Does that include the 30 A HVAC BLO fuse in the rear underseat panel?

....I have the auto heating system upgrade,

I have no idea what that is.

....so it doesn't have a resister or a relay, it has a blower motor control module that is connected to the side of the blower motor plenum.

GM/Cadillac stopped using resistors for blower motor speed control (at least for Sevilles) more than 10 years ago.

Today's standard control method for many systems is Pulse Width Modulation (PWM) at a frequency somewhere near 2 KHz.

....From what I understand....The bare wire supposedly sends a square wave pulse to the motor that actually controls the motor and speed.

Not exactly accurate.

Can you tell us the voltage value you read between pin B (purple wire) and pin A (black wire) at the blower motor connector coming from the blower motor control processor?

You "should" see something close to 12 Volts with the fan speed manually selected to maximum. Manually toggling the fan speed to lower settings will reduce the voltage reading.

If you are able to jumper in an external source of 12 Volts to pin B (+) and pin A (-) of the blower motor side of the connector, you could determine for sure whether or not the blower motor has failed (which I suspect) without throwing any more parts at the problem.

Jim

Drive your car.

Use your cell phone.

CHOOSE ONE !

Link to comment
Share on other sites

All I can tell you is that 9 out of 10 times the blower motor is at fault.

x2

And not cheap from what Ive heard anyway

* 1966 Deville Convertible

* 2007 Escalade ESV Black on Black

* 1996 Fleetwood Brougham Black on Black V4P -Gone
* 1983 Coupe Deville Street/Show Lowrider -Gone

* 1970 Calais 4dr Hardtop GONE
* 2000 Deville DTS - Silver with Black Leather and SE grille GONE
* 1999 Seville STS - Pearl Red GONE

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...