Blower fan intermittent; changes fan speeds on its own

[big_news_1]

Not sure if this is a problem with the blower fan itself or the climate control unit. First of all, the fan is intermittent. Sometimes when I start the car it turns on, and sometimes it doesn't work at all. Sometimes if I turn the car off and open the door, then close the door and start the car again it will work. On the days it does work I seem to have no control over the fan speed. Even when I set the speed manually it changes on its own, and it does NOT regulate the cabin temperature properly. Often it will blow harder when I first start the car but slow down to a trickle of air within 20-30 minutes. Sometimes it will then speed up again on its own, despite the fact that the fan speed is manually set to the highest setting the whole time.

Ideas?

[Echo SSEI]

Not sure if this is a problem with the blower fan itself or the climate control unit. First of all, the fan is intermittent. Sometimes when I start the car it turns on, and sometimes it doesn't work at all. Sometimes if I turn the car off and open the door, then close the door and start the car again it will work. On the days it does work I seem to have no control over the fan speed. Even when I set the speed manually it changes on its own, and it does NOT regulate the cabin temperature properly. Often it will blow harder when I first start the car but slow down to a trickle of air within 20-30 minutes. Sometimes it will then speed up again on its own, despite the fact that the fan speed is manually set to the highest setting the whole time.

Ideas?

Fan motor could likely on the way out. I had similar symptoms not too long ago. I kept a prybar in the trunk and if the blower motor didn't work when I started the car, I gave it a tap with the prybar. Eventually, even giving a good rap with the prybar stopped working and I repalced the unit. Very simple job. Your experience opening and closing the door and having it kick on may be similar to giving the motor a "bump" to get it jump started.

[imidazol97]

Not sure if this is a problem with the blower fan itself or the climate control unit. First of all, the fan is intermittent. Sometimes when I start the car it turns on, and sometimes it doesn't work at all. Sometimes if I turn the car off and open the door, then close the door and start the car again it will work. On the days it does work I seem to have no control over the fan speed. Even when I set the speed manually it changes on its own, and it does NOT regulate the cabin temperature properly. Often it will blow harder when I first start the car but slow down to a trickle of air within 20-30 minutes. Sometimes it will then speed up again on its own, despite the fact that the fan speed is manually set to the highest setting the whole time.

Ideas?

This sounds like the blower control module. You imply that is does have the automatic temp and speed control.

You should do a direct connection to the blower motor itself with a fused cable from the battery and ground.

You might clean the connections at the blower control module. I believe there's a feedback to the unit so it "knows" what speed the fan is running. A poor connection might be giving variable feedback values.

[Echo SSEI]

Ben, If you want, we could swap out my blower control module with yours, as a test, before you sink $ into a new one (dang, those suckers are pricey )

[BlackHawk99]

Is the actual fan changing speeds? Meaning, can you hear the fan slowing down? It could be that the fan is not changing speeds at all, just the air flow is changing directions. I had vehicle once which would have the same symptoms as you're describing. However, the air was coming out of the defrost and trickling out of the dash and floor vents. It was a vacuum tube which needed to be replaced.

[big_news_1]

Is the actual fan changing speeds? Meaning, can you hear the fan slowing down?

Yes, it appears to be slowing down almost to a dead stop. When the airflow begins to taper off I usually check the defrost/heater vents to see if it is being redirected, and it's not. The fan is simply changing speeds for no apparent reason.

[big_news_1]

This sounds like the blower control module. You imply that is does have the automatic temp and speed control.

Yes, it has the electronic climate control, but even controlling the fan manually yields an inconsistent speed.

Is the 'blower control module' the dash-mounted climate control unit, or are you referring to a separate box?

[sonoma_zr2]

Ben, it is in the engine side of the firewall, under the fuse panel.

[imidazol97]

Yes, it has the electronic climate control, but even controlling the fan manually yields an inconsistent speed.
Is the 'blower control module' the dash-mounted climate control unit, or are you referring to a separate box?

The blower module is where the resistor unit is in this diagram. Hope it helps.

[1fatcat]

Sometimes if I turn the car off and open the door, then close the door and start the car again it will work.

Check that ground splice pack under the drivers door sill plate and carpeting. My blower motor did this krazy act too when my grounds went bad. You might be disturbing it enough to give a little more connection from the vibrations when you open and close the door? I fixed the ground and replaced the leaky door gasket and now all is good.

[big_news_1]

Over the weekend I checked out the ground splice under the driver's door sill, but everything looked fine. Wiggling wires around made no difference, as the fan would still not work.

I then removed the blower motor resistor, which was pretty dusty and dirty. However, I wasn't sure what to do with it. It appeared to be a self-contained unit with heatsink and resistor all built into one. I took it to Autozone and was unable to find a matching part name or similar part.

I cleaned up the unit a little and made sure all the electrical connections were free of dust and debris, then reinstalled it. Lo and behold, the blower has been working normally since then! I really didn't do any specific repairs to the resistor; perhaps it just had an intermittent connection that needed to be cleaned and re-seated. Whatever the case, it is a good example of the resistor causing intermittent functionality.

I will update this post if anything changes over time. Thanks for the help, folks!

[Echo SSEI]

Glad to see you got it working, Ben. So, what did you clean it with?

[big_news_1]

I used a wire brush, Bob, but apparently is wasn't enough!

Unfortunately the blower is intermittent again. It worked great for about a week, then started acting up again.

Generally it works fine when I initially start the car, but the airflow gradually reduces to a trickle over the course of 15 minutes. The fan speed still indicates the highest setting on the ECC while this is happening. I have checked the floor and defrost vents, and this is definitely not an issue of the air being redirected.

I suppose the next step is to try a junkyard resistor. Anyone have another suggestion?

[Echo SSEI]

Again, if you want to swap out the module from my car, to test, you can, but it seems that you indeed need a replacment module. They really aren't servicable from what I have read.

[1fatcat]

Did you clean both ends of the connection? Check for loose terminals where the female terminal has opened up or corroded.

[big_news_1]

Did you clean both ends of the connection? Check for loose terminals where the female terminal has opened up or corroded.

Both ends? Meaning I should have followed the wires to their termination point and cleaned them there? No, I didn't... I think those wires join another bundle and head up to the main harness. I could be wrong, though.

Additional note: It seems like I can hear a tiny bit of mechanical clutter/clunking deep in the dash when I turn the ECC on and off. I'm not sure what this would be or what bearing it would have upon air velocity from the vents.

[1fatcat]

I mean check both ends as in, the wires and the hardware that the wires plug into. So, the resistor and the wire connector. That clunking noise may be an HVAC actuator? Does it sound like a timed knocking? Like small plastic gears that are stripped out and skipping against another gear?

[big_news_1]

New development:

As the blower starts to slow down to a trickle, I've noticed it momentarily speeds up if I'm turning the steering wheel to the left. It could be going around a corner, or even a gradual left curve on the freeway (i.e., does not require sudden or violent movement). Doesn't seem to do it to the right, or at least not as noticeable.

What on earth is going on?

[sonoma_zr2]

maybe you have a bad fan Ben. Put 12V directly to it and let it run a little. Does it's speed stay constant? If you have a way to put 6V on it try that also.

[big_news_1]

What's the best way to do that, Travis?