: '78 Deville--fan works on low speed only



pompste
06-12-10, 02:34 AM
After replacing 2 blower motor relays and installing a new blower fan---the fan blows at LOW speed only now----better than nothing,but i`d prefer to have it blowing at high speed on hot humid days and in the winter.
This problem is frustrating,to say the least.
Any suggestions will be appreciated.

pompste
06-13-10, 02:59 AM
Apparently---everyone`s as stumped as i am.Maybe i can run a manual direct feed somehow--bypassing all the internal electronics.
I want the fan to run at high speed someway,somehow.
Possible blower RESISITOR may be the problem.

deVille33
06-13-10, 08:31 AM
At one time I had a problem with one of my control units, and after a little research in the SM I found a module in the control unit which seemed to be the culprit. I traded it out with another module and the fan control worked properly. I don't remember the problem or which module. You really need a Service Manual to help you out. This section of the Service Manual is quite extensive and covers a lot of circumstances and area.

pompste
06-14-10, 01:11 PM
At one time I had a problem with one of my control units, and after a little research in the SM I found a module in the control unit which seemed to be the culprit. I traded it out with another module and the fan control worked properly. I don't remember the problem or which module. You really need a Service Manual to help you out. This section of the Service Manual is quite extensive and covers a lot of circumstances and area.


Where is the "contol unit" located? Where can i get a service manual?

I was surprised yesterday,when for a about an hour,all fan speeds worked correctly! Did`nt last long though--after i turned the ignition off and parked it for a while,then started it again---the fan returned to working on low speed only.

77CDV
06-14-10, 02:08 PM
Go. Buy. A. Factory. Service. Manual. E-bay. Cheap.

deVille33
06-15-10, 08:53 AM
Where is the "contol unit" located? Where can i get a service manual?

Here, I'm talking about the dash control unit. I was trying to understand the system better and tried to apply what I was reading in the SM to practical application. From what I was reading, I suspected this module in the control unit to be the problem, so I traded it out with another module.
Most people just buy another control unit and plug it in. Problem solved, but to understand the system better, you have to go a step further.
I think the Cadillac Climate Control system is a little more sophiscated than the other GM lines due to the control unit, so in order to understand this system, you really need the Cadillac SM. The SM has a lot of reading, a lot of diagams and schematics.
I don't know anyone who is able to diagnose distinctly what is wrong with a system just by discussion, it's too extensive and involved.