Trailblazer A/C FAN Issue

[Daniel644]

OK so i've got this issue, happened once a while back then again last week one day and now it's been like this for several days this week.

the Interior Fan (that blows the air through the vents) only works when cranked all the way up to 5 (Max) 1, 2, 3 and 4 do nothing.

 

[Mooseman]

You need a new resistor pack.

 

[Daniel644]

You need a new resistor pack.

so this thing https://www.autozone.com/cooling-he...lower-motor-resistor-dr755/604006_0_4222_8531

should I also drop the motor and clean it out while i'm down there? trucks got almost 240k miles on it. Looks fairly easy to do from the videos I just looked at.

 

[Mooseman]

That would be the part needed if you have the manual HVAC (which I assume you have since you say speed 1-2-3-4-5). Not a bad idea to drop the fan itself and give it a good cleaning.

Do inspect the wiring for anything burned. Another possibility is the speed selector switch but this is not so prevalent on this platform. If the resistor pack doesn't work, the switch would be next.

 

[JerryIrons]

Check your fuses as well, I seem to remember that the 5 setting has it's own fuse separate from the others. Also an old blower motor can cause higher current draws, so like mooseman said make sure you look at the wiring to see if anything has gotten hot.

 

[Daniel644]

I went ahead and picked up the resistor pack today on my way into work, weather permiting (we are getting thunderstorms on and off all day today) I will get in there tonight and swap the resistor pack and inspect the wiring.

 

[Daniel644]

OK, resistor pack replaced and all fan speeds work again, no sign of overheated terminals on any of the harness's, but I don't think this is the first time that resistor has been replaced, there is a sticker on the old one that has what appears to be a date of September 6th 2004 and this truck was built in early 2003. Might just replace the fan motor for the hell of it just to be on the safe side (do they slow with age?)

 

[Mooseman]

It could draw more if it's getting stiffer to turn so it's not outrageous to think it might be contributing to the failures. However, this one lasted 15 years so not a bad run. It could have been replaced on warranty early in its life due to a premature failure.

What year is your truck? No indication anywhere.

 

[Daniel644]

What year is your truck? No indication anywhere.

2003 model year, just wondering if it might be worth swapping the fan, even before the resistor pack failed the strength of the fan feels weaker then when I got the truck 4 and a half years ago, like the number 1 fan speed is less air through the vent then the amount of air that comes through the vent when you crack your windows doing 45 MPH.

 

[Mooseman]

It's possible the bearings in it are going. If 1 is so low you can't feel it, I'd swap it. Another possibility is the evaporator is clogged with dirt and debris. When you take the motor out, if you have a boroscope, have a look in there.

Another reason to do the filter mod IMHO.

 

[JerryIrons]

Well if you go with what you have now, and then your resistor blows again in a month or so like mine did, you'll have your answer about what to do about replacing the blower motor

It's too bad we don't have a way to test out a blower motor regarding resistance or current draw to indicate if it needs replacing.

 

[Daniel644]

It's possible the bearings in it are going. If 1 is so low you can't feel it, I'd swap it. Another possibility is the evaporator is clogged with dirt and debris. When you take the motor out, if you have a boroscope, have a look in there.

Another reason to do the filter mod IMHO.

I need to get a boroscope but never have, can I reach in and feel around? I thought about getting the cabin air filters in the past as being an 03 I have the door and don't have to cut anything but was concerned it would restrict flow to much and it's not that I can't feel the 1 speed, it's that it's roughly equal to the natural airflow through the vent when the windows are open, but when parked where you wouldn't have that natural airflow you can feel it, it's just about the same strength as the natural airflow.

 

[Mektek]

Yes, you should remove and clean the blower cage. You can also relube the bearings if you want to give it a bit more life. At that mileage there probably are leaves and twigs inside. While the motor is out you can look into the evaporator - but it's probably a good idea to clean it out with a pressurized detergent solution and some brushing.

02 still has resistors, even with the automatic system.

 

[Daniel644]

OK, just pulled the blower, no debris to speak of, just a layer of caked on dirt on the fins. while it's out I decided to take a video of me spinning it by hand to see how long it spins for so if anyone here has replaced one and can compared the amount of time it spins for here is a link for said video

I have a Rigid Shop Vac where the motor detaches and functions as a leaf blower, i'm gonna blast that through the evaporator during the day tomorrow (technically later today since it's 3:30 am) and maybe try like a "reverse flush" by blowing into the closest vent or something, we'll see omce I have light to work by.

 

[Mektek]

If there is a significant amount of debris on the evaporator it will probably be literally glued to it. After many cycles of the wet evaporator with dust and dirt it makes a paste that dries and sticks to the metal fins. Don't blow it - you might impact the debris deeper into the core. Maybe vacuuming with a brush head might be OK if you have good enough access.