Originally Posted by imidazol
If you have the auto temp control system with a digital readout, then you have a power feed to the blower control module that goes through fuse A3 in the Relay Center, a 30A. fuse.
It also has two other related fuses that go to the programmer which feeds the voltage to the lblower control module: Fuse 5A for 15 Amperes whic is labeled also as Aut A/C Cruise; and Fuse 9C which 10 Amperes and labeled MSC/RDO/CLSTR. The last one is keep alive, I believe.
There is no separate relay that powers the high speed setting with direct current from the battery instead of through a resistor pack as is on the basic HVAC unit.
Have you tested the blower motor itself? Always start with the simplest explanation. Law of Parsimony.
EDIT: I missed a fuse. There'* a fuse in the right side passenger fuse/relay block. It'* #11 and is 10 amperes. It'* the feedback fuse from the line to the blower motor that tells the programmer what voltage is b eing applied to the motor by the blower motor control module.
I was hoping someone could help me finish a similar diagnosis. I have a '98 Bonneville SE with the automatic push button HVAC controls (digital readout) and the other day my blower motor stopped working. The display screen shows it should be running, but the fan does not work.
So far I have done the following.
Manually bypassed the blower fan with 12V and it works fine.
Checked all the fuses listed above. All are in good condition.
I pulled the blower control module out of the blower box. Now here is my question. How do I diagnosis if this part is bad, or if it is getting an incorrect signal?
Here is what I saw on the plugs that go into the blower control module (while unplugged) with the ignition ON and the blower / heat turned ON per the display screen:
Red Wire: 12V
Purple Wire: 1.86V
Black Wire: 0.05V
Grey with Black Stripe: 8.7V
Here is a pic showing the plugs I am referring to:
With the ignition and blower off, the Purple/Black & Grey with Black all go to 0V.
The reason I am confused is that when I turned the fan "up" to high, and then "down" to low, there was no change in the readings I saw at the plugs. I figured there would be some change in voltage, but perhaps it is a resistance circuit. I don't know. Can anybody help???