In our '92 Buick LeSabre the a/c fan blower motor continues to run despite trying to turn it off inside, and even after the ignition is turned off. After some research on the internet, I read about this being a common problem related to the Blower Motor Resistor/Fan Control Module and it should be replaced. I bought a used part for our '92 Buick (with automatic temperature control) for $55 with a 90 day warranty (new-$225) and installed it myself. It worked for 2 short car trips within a 24 hour period after which the same problem with the blower motor remaining on occurred. It seems that the problem is most likely in some electrical spike or short causing the part to blow since the same problem occurred with the original and the new (used) part. My question(s) is: at this point should I get someone to just wire up a toggle switch directly from the power to the fan motor that would be able to turn on and off the blower motor as needed, or take it to my mechanic who would charge me $75 an hour to diagnose the problem plus the cost of the part? What would you advise me to do for this 18 yr old car which otherwise runs pretty well? Thank you, gmazzeo
The trouble you are having may be due to the blower motor drawing too much current and it is damaging the speed controller module. I suggest you have the current draw of the blower checked before trying to fix the trouble again. If the current checks out ok then I suggest you purchase a new speed control module. I think a new solid state speed control module should only run about 120 dollars for the part. You shouldn’t need to replace the whole HVAC controller in order to fix this.
You have to expect repairs like this on a car that old. Things do go bad after time, even on newer cars. If other things on the car are in good shape you should be able to keep it going for a while without a lot of repair bills. When you get into real expensive engine and transmission repairs it may be time to consider a newer car at least.
Thank you for your quick reply. The suggestion to have the current draw of the blower motor checked is a great idea, but if it checks out OK, why would I want to put in another Speed Control Module after damaging the two previous ones? Are they not damaged? Aren’t Blower Motor Resistors, Fan Control Modules, and Speed Control Modules just different names for the same part? Also, if the blower motor IS drawing too much current, I assume that it’s time to replace the motor. But, wouldn’t I still need to put in a new Blower Motor Resistor (Speed Controller) after determining the faulty blower motor? If I could have found a new Blower Motor Resistor/Speed Control Module for $120 I would have never spent $55 for a used part (though I still may be able to return it for a refund or exchange). Do you know where can I find one for that price on a '92 Buick LeSabre with automatic temperature control?
If the motor current checks out ok then there may be an air flow problem causing the trouble. If the blower motor has never been replaced it may be a good idea to replace it anyways.
The speed control module needs air flow to cool it so check for things like a mouse nest in the ducting. The speed controller I am refering to is a solid state device that has perhaps 3 or 4 lead connections and fits inside the air duct. I am not talking about the main controller that fits in the dash with the controls on it. Here is a link to what I am refering to.
OK. We are talking about the same part that I replaced which only worked for a short period of time. It’s the top Motor Blower Resistor on the link for $144.98 and it has two sockets, one with 3 leads and the other with one lead. It’s located under the hood and mounted vertically into the firewall. I will be checking next for the current being drawn from the blower motor (not sure how many amps it’s suppose to draw but think it might be about 7 to 15, maybe the fuse box will help) and looking inside the firewall for any possible air obstruction. If the fan motor were drawing an excessive amount of current the Speed Controller/Blower Motor Resistor would have totally blown and stopped working, but that is not the case since the blower motor still runs. Right? Without any conclusive evidence, I’m definitely reluctant to buy another speed controller/blower motor resistor and plop it in. What about my idea of running a toggle switch directly to the fan motor to shut it on or off as needed? This way I could use one of the 2 partially blown blower motor resistors as is.
From what you have mentioned about the solid state modules it appears both of them have failed in the shorted condition, not the open condition. Since the modules are connected to the battery without any switching that allows the power to be applied to the blower motor when the modules internally short the input and output terminals together. You could put a switch in series with the power lead but there will only be one speed for the blower, full speed. If you do that then there is no need to install the module except to block the vent hole. Just jumper the power input and output wires together.
As far as normal current draw for the motor I would guess it may be around 10 amps at full speed. To check the current of the motor you are going to need a meter that can safely handle around 20 amps of current. Most high current meters can handle 10 amps so you may need a shunt to read the current. You can measure the current at the fuse connections for the blower and replace the fuse with the meter connections. That will allow you to measure the current draw of that fuse connection. Since the blower fuse isn’t blowing out then I would guess that either the airflow for cooling the module is partially blocked or there are excessive voltage spikes being generated from the blower motor causing damage to the module. It may be a good idea to replace the motor also so there is no question about it.