heater and a/c blower quit working

[Jeff Stovall]

My 1995 LaSabre had a problem yesterday when I went to shut off the ignitiion and the heater/a/c blower would not shut off even with the key removed. Everybody jumps to the "bad blower relay" answer, don't go there yet!! I left the car running because I was out running errands. After a couple of stops and leaving the engine running to ensure the battery did not run dead, on the way home the blower quit running altogether and would not come back on regardless of what the controls were set to, including using the manual override method by trying the front window defrost pushbutton. All the control switches appear to be working working.

My questions are as follows.

1. I hear conflicting data that the 95 LeSabre has a "Blower Control Module?? IF SO, where is is located??

2. If it has a Blower Control Module, does that mean it has not Blower Relay in the Multiplex Relay panel under the hood?

3. If it is a relay problem, how can if figure out which relay it is, the car manual says there is a diagrahm under the multiplex cover, but it is not there??

3. Please suggested troubleshooting plan.

[HotZ28]

First of all, if you have auto climate control (ACC) you have a blower control module and do not have relays for the blower. The module will fail sometimes due to high amperage draw from the fan, but not always. I have seen them fail even with a new fan motor. It does not hurt to test the amp draw on the fan motor before you replace the module. It should be around 17-18 amps on high speed and not more than 22. If it is pulling more than 22 amps, replace the motor.


The "blower control module", is located on top of the fan box under the fuse and relay section on the firewall. It has two wiring connectors connected to it and usually three screws holding it in the box. You can get a new one from any dealer for around $150.00. It is such a common problem on Buicks and other GM cars with auto climate control & fan control, that the dealers usually keep a good supply on hand. You can also check your local salvage yard, (about $50.00) they usually have some at the front counter. Be careful to insist on the same part number as the one you have removed if buying from a salvage yard. (The part number will be on the module). GM made four or five different controllers that look the same, however do not have the same number of wires or the same functions.

You do not have a relay for the blower fan because the controller module sends variable voltage to the fan motor to control the speed. Usually the resistors fail in the module and the default voltage is 12V direct to the blower, unswitched, therefore, your blower runs all the time unless you pull the fuse, disconnect the battery, or pull the plug on the fan itself. They also fail in the no run mode, or intermittent mode. The fuse is also located on the firewall with the relays. Pull the cover off and look inside the cover to locate the correct one. It is a 25 or 30 amp fuse.

I have also found that Advanced Auto parts (part# RU304) and others are now selling a new module for around $100.00.



Shown below is a pic of the module;

[Cornchip]

I can only speak of my own experience on my 1995 LeSabre Custom. It looks like 2 different blower systems were used on Custom and Limited models. Since my car is just a Custom I will speak only about that. It uses a blower motor with a single winding that blows full RPM with full 12V+ applied. Any other speeds are handled with a "resistor" module found under the hood in the blower housing. The module need to have air blown over it to stay cool enough that it won't melt down. That said...check the motor first by using jumpers supplying power from the battery. If that is fine check the resistor module for burnt out coils. If on visual inspection they appear fine...check for power reaching the control panel itself (dash unit). The dash unit controls 2 different relays found under the hood....one the 12V source that feeds the fan speed switch (ON/OFF lower left corner) and the other escapes me right now...I'd have to check my shop manual. Anyways...to make a long story short..I had no speeds availble to my fan speed switch...but the relay was supplying power to the switch circuit. That meant to me that somewhere between the relay and the switch there was a disconnect. To fix this I ran a new wire from the relay to the switch and problem solved.

I hope this hasn't caused to much confusion...message forums will do that as many times situations are unique. If you have continued problems let me know...I can scan the shop manual for the correct electrical schematic for your application. This should help you to better diagnose you problem.