Repair common AC blower control module problems. Drivers of some popular Chevrolet trucks and sport utility vehicles are having issues with intermittent interior fan operation.
In fact, I had one situation where the blower fan got stuck on high even when you turned off the ignition key.
However, it seems like the most common complaint remains that the fan doesn't respond to speed adjustments or doesn't work at all.
Some of the more popular vehicles included in this issue are the Chevrolet Silverado pickups, Trailblazer, Suburban and Tahoe sport utility vehicles.
Of course, this applies to the GMC version of these trucks like the Envoy and Yukon. The model years with the most problems are from 2000 through 2006.
Some might say that this isn't considered an old ride. Still, these vehicles are approaching 15 to 20 years old. I was working at a Chevrolet dealership when these cars were still under warranty.
We started getting complaints of intermittent operation as the vehicles were heading out of the three year 36,000 mile base warranty period.
An interesting note, customers that complained about this problem without resolution had their situation documented while under warranty as no problem found. When the issue became common those customers were able to extend the warranty and receive the covered repairs.
Unfortunately, we didn't have the updated parts available at the time, like we do today. Here we'll discuss these second design improved components and some best practices for pinpoint diagnosis and installation.
Although prices may vary around the country, I can say that if you rolled into a dealership, this repair could cost a couple of hundred dollars. With new parts available for around $60 the replacement of the AC blower control module is within the skill level of many do-it-yourself mechanics.
Now that we're getting into the complaint, cause and correction part of the article we need to clarify something.
A blower control module is only fitted to an automobile that has automatic temperature control or ATC. This is the digital type that function like the HVAC control panel in your house.
You set the temperature to 70 degrees and the climate control system automatically adjusts the temperature doors and blower speed to accommodate your settings.
If your vehicle has the base option set up with two dials and slides to select a temperature range between cold and hot, you do not have a blower speed control module. Instead you'll have a blower resistor assembly.
Nevertheless, both of these systems are troublesome and might need their respective parts replaced at some point. However, It's important to make sure you know the difference and what parts are on the automobile.
On the automobiles we're discussing you access the blower module from the passenger side floorboard area. On vehicles with high-level trim there might be a hush panel to remove to gain access. Another thing to take note of is that on these models the glove box will swing out of the way.
All you have to do is push up on the stop tab in the upper left corner of the glove box compartment.
When this swings out of the way you have an excellent view of the blower motor and its two wire connector.
Although you probably have a bad AC blower control module you still want to take a few basic tests before you purchase the replacement parts.
You want to check the fuses to make sure they aren't blown. If they are blown it could be a sign that the module is drawing too much current. The next step is to check for power and a good ground at the blower motor connector.
Although it's likely that you have a module issue there’s still a possibility that the blower motor itself could be bad. With the key on and maximum fan selected, you should have 12 V at the blower motor.
If you do and the fan is not moving give it a light tap on the motor housing and see if it starts to spin. If it does you should still replace it.
More than likely you won't have power at the blower motor. Now it's time to locate the blower control module which is on the lower side of the heater case. Think of the blower control module as the middleman.
It has a three wire connector from the AC control head going into it and the two wires that connect to the blower motor coming out of it.
If you have power and ground going in and nothing coming out when you have selected max blower on the control panel, then you have a failed AC blower control module. If you have no power at the three wire module connector then you might have an issue with the air conditioning control head.
As I mentioned in the opening there’s a redesigned replacement module. Despite the part looking quite different from the original it does bolt right into the original ones mounting location with no alterations necessary.
You can see that the heat sink area that protects the device from overheating is one of the major changes in the new design. The replacement part also has a different connector setup and will require the splicing of the three wires that we tested earlier from the control head.
There are a couple of things to note about cutting off the old connector. To be on the safe side you should disconnect the battery.
What happens if you cut all three wires at the same time? You're actually shorting power to the ground and you will blow the 40 amp AC fuse.
Although it's not the end of the world I'm sure you don't have one on hand and the new one costs about five bucks. So you can either disconnect the battery or you can make sure to cut one wire at a time so you don't take out any fuses.
The other thing to mention is the kits I've seen have come with no connectors. This means you'll have to pick some up at your local auto parts store.
I'm a big believer in soldering all automotive wire connections. However, that's probably overkill for this situation and not everybody has a soldering kit handy. The use of a good quality butt splice connector with a heat shrink tube should take care of the three wire repairs just fine.
A lot of vehicles from the early 2000s are suffering with blower motor resistor failures. Not just the Chevrolet products that we discuss here, but Dodge vehicles and even some foreign cars are having the same issues. It seems like the culprit is heat buildup.
Most of the cars with these issues now offer replacement parts with larger heat sinks to dissipate the buildup. Therefore this is a repair you're only going to have to do once during the ownership cycle.
Although it's tempting to go ahead and buy the replacement part without performing any diagnosis it's not recommended. Learn more about air conditioning systems on older cars.
There is a possibility that the blower motor itself is the root cause. And there's even a small chance that there might be a problem with the AC control head that sends the signal to the AC blower control module.
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Author bio : Mark Gittelman is a retired ASE certified master technician, Chevrolet Professional Service Council member and the founder of FixMyOldRide.com. Watch the video on the about Mark Gittelman page to see his credentials, awards and certifications for yourself. Mr Gittelman hand writes all of the articles on FixMyOldRide.com unless indicated otherwise.