Heater/AC control module???

[walksontop]

I've been researching heater problems on the web concerning my 1997 Buick Lesabre. It is beginning to look like the Heater/AC control is the problem. (I Think). Not only do I not know what in the world that is, even if I did know, I wouldn't know where to find it., could be the blower also, however in the process of failing, the blower always was strong when it did come on. The heat/ac was a long time in failing, 6 months at least before it stopped completely. It was an intermittent thing even when you could get it to come on whether you were on heat mode or cool mode. At the end it would cycle on and off even while you were driving. The button controls on the dash for fan speed, temp adjustment, and air high/low position all seem to work just fine., at least that is what the digital read out is indicating. How might I test the blower with out hurting some other circuitry. Also, what and where is the control module? for this car??

thanks Bob P.

[LeSabre97mint]

Originally Posted by walksontop

I've been researching heater problems on the web concerning my 1997 Buick Lesabre. It is beginning to look like the Heater/AC control is the problem. (I Think). Not only do I not know what in the world that is, even if I did know, I wouldn't know where to find it., could be the blower also, however in the process of failing, the blower always was strong when it did come on. The heat/ac was a long time in failing, 6 months at least before it stopped completely. It was an intermittent thing even when you could get it to come on whether you were on heat mode or cool mode. At the end it would cycle on and off even while you were driving. The button controls on the dash for fan speed, temp adjustment, and air high/low position all seem to work just fine., at least that is what the digital read out is indicating. How might I test the blower with out hurting some other circuitry. Also, what and where is the control module? for this car??

thanks Bob P.

Bob

Sorry I don't know where these items are located. However, I do know that your heater control can be checked for proper operation with a computer just like the engine can be checked.

Regards
Dan

[HotZ28]

With the info you used to describe what is happening, I am not exactly sure what your problem is; blower not running while in the on position, or the compressor cycling off-on. If the blower motor is the problem, you need to replace that first. If the motor is in good shape and not pulling over 20 amps on high, you could have a bad module. That is what I described below.

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 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 sends variable voltage to the fan 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 located on the firewall with the relays. Pull the cover off and look inside the cover to locate the correct one. It is a 30 amp fuse and labled "AC". I have also found that Advanced Auto Parts is now selling a new module for around $100.00, part # RU304 Standard products. It looks like this;

[imidazol97]

I believe Z28 is right on with the answer.

If you are saying the vents don't direct the air correctly at times and change where the air is sent in an on and off way, I'd try to see if it was the programmer box below the glovebox on the heater box.

But you're saying it's the fan blowing the air the cuts in and out, if I understand. That's the part Z28 talked about or possibly the motor itself. But you don't comment about motor noises from worn bearing or dry bearing.

Our blower on 98 LeSabre started giving strange speeds whether on manual setting or automatic. Sometimes it was barely turning, sometimes almost normal speed for the setting. Some days it worked; some days it didn't. If I had know about this site and the people on here who could have helped, I'd have saved a couple hundred or little less dollars. I don't recall the cost now. The dealer did have trouble getting the circuit module to test out as bad, so they did put in some time.