This 2002 Buick Century came in with the complaint that the lower blower speeds do not work. This Century has manual air conditioning controls. I have been down this road many times and it is just a faulty blower resistor. I will give actual testing information later, but for now I am just going to concentrate on changing the resistor.
First of all the blower resistor is located under the passenger side of the dash. There are a total of three push pins that need to be removed. Two along the leading edge.
One underneath, towards on the left side as shown below.
Once the panel is loose the courtesy light needs to be removed if present. A simple left turn and it comes right out. Remove the panel and position the light out of the way so that it will not burn you or anything else. If you are smarter than me, you will probably pull the fuse or bulb.
The blower resistor is located beyond the blower motor in the picture below. It has the seven wire, multicolored harness attached to it.
In the next picture I show the connector that goes to the blower motor. It has a locking tab that has to be depressed with a small screwdriver or other device. Then the connector can be wiggled out of the blower motor receptacle.
The seven wire connector has a latch on the outside of it, that has to be pulled slightly away from the resistor body, while the connector is pulled straight down. Tuck the harness out of the way while you continue to work.
Now using a 5.5 mm socket and ratchet, remove the leading screw from the blower resistor as shown below.
The next picture shows the removed screw, and the reason I make a point of showing it to you, is so you will have an idea of how much the screw would move with one full turn (the space between the threads).
Now bring the harness connector for the blower motor, that is attached to the blower resistor assembly, around the larger harness as shown below.
Now for something that is a bit unorthodox for me. With your hand or a pair of pliers, pull the harness towards you, until the resistor pulls loose of the two front mounting screws. For many years I fought with sockets, swivels and extensions to try and remove the two front screws.
There are two slots for the forward mounting screws as shown in the picture below. Do not pull it with the intent of moving it a great distance. Just a firm pull to let it move about a quarter to a half an inch. If you pull too aggressively, you will wind up having to pull the broken pieces of the resistor board, out of the main a/c housing.
If you look closely you will see the two forward mounting screws.
The new resistor on the left and of course the old resistor on the right. Notice that the interior resistor parts have been redesigned and are much heavier.
It is a little hard to see, but if you double click on the picture below you will see that I am using an open end wrench to slightly loosen the forward mounting screws. They only need to be loosened 1/4 to 1/2 of a turn. Doing this, while unorthodox, will allow the resistor just enough room to slide under the heads of the screws.
There should be just a slight bit of resistance as you push the resistor front edge under the two mounting screw heads. If it feels too easy, pull the resistor back out and tighten the screws slightly. If it seems like to much force will be needed, loosen the screws just a little bit more. It should feel like the detent when you close a tool box drawer. Now install the single screw closer to you and connect all of the wiring. When connecting the wiring, be sure to properly align the connectors and a straight and direct force to push it into place. You want to avoid wiggling, while removing and installing these connectors.
If you need one of these resistors please click here.
If you want to test the circuits coming in, it will be as follows:
- Terminal “A” Tan = Speed 2, power through blower switch from Low Blower fuse, 20 amp, Ignition
- Terminal “B” Yellow = Speed 1, power through blower switch from Low Blower fuse, 20 amp, Ignition
- Terminal “C” Purple = Speed 4, power through blower switch from Low Blower fuse, 20 amp, ignition
- Terminal “D” Lt Blue = Speed 3, power through blower switch from Low Blower fuse, 20 amp, Ignition
- Terminal “E” Black = Blower system, ground at all times
- Terminal “F” Small Orange = Speed 5, power through blower switch from Low Blower fuse, 20 amp, Ignition
- Terminal “G” Large Orange = Speed 5, Constant power from High Blower fuse, 30 amp, Battery
Fuses are located in the interior fuse boxes.
how do you tighten the front screws, can’t see nor barely see them. thanks for pics, helped tremendously, still could not tighten front, tried different ratchets also?
If you are sure that the resistors have failed and not another problem, the likely causes would be a faulty blower motor(drawing too much current), restricted air flow through the evaporator and/or heater core and water intrusion.
Help needed.
Blower is now working on 1999 buick century.
I replaced bower resistor twice but resistor is over heating and highest setting does not work.
Any suggestions???
Thank you for all the great info.
After removing the resistor assembly, remember to slightly loosen the two front screws. They are easy to get to with the resistor removed and it will make it much easier to install the new resistor. With the resistor back in the hole, it is not too difficult to snug up the two front screws.
Thanks for the sharp photos and useful tips. My 2003 Century has its lower fan settings functioning again. After removing the 1st screw, the unit will not slide away from the firewall because it is recessed in about 1/4″. The pulling on the wires helps the edge of the unit clear the obstruction. A pair of pliers helped me slide the unit out. It’s helpful to remember that a little damage to the old resistor unit or its wires won’t matter.