Blower doesn't blow

[6716]

Drove to run an errand, everything was fine. Got back in the truck, blow motor speed selector on the console was at 0, fired up the engine, turned it up to 5, it blew for half a second and then quit.

Pulled the fuse, looked good but put a new one in anyway and still no joy.

I replaced the resistor many many moons ago, but that was after slowly losing the lower speeds on the blower, which did not happen this time.

I'm kinda thinking it might be the motor itself. I guess I pull it and ... do I check continuity or what? It is colder than a witch's tit out there right now, hoping to be smart and not spend a bunch of time and cash shotgunning parts.

Anything else I should check or think about?

Thanks

 

[Reprise]

Do these things have a relay as well as a fuse (& resistor, like you already know about) ? If so, you might be able to swap it out and see if you get the fan back.

If not, maybe (and that's a big 'maybe'), disco'ing the battery for 5 min.
If that doesn't work, maybe sourcing a (used) control head (especially if you've got the auto climate, but sounds like you don't, since you have a numeric fan speed indicator).

Yeah, you'd have to check resistance on the fan motor, as well as continuity. I don't know the values offhand, but they'd be in the service manual. Or someone has probably posted a YT vid somewhere. Or someone here has it in a thread.

Hope you get it resolved quickly. It's going to be super cold here (IL) for the next 10 days -- prolly in your neck of the woods, too.

 

[Mooseman]

Using a test light, check for power at the motor connector. No power, likely the resistor pack again. If there's power, test the motor with a separate 12V power source.

 

[Chickenhawk]

If you had to replace the resistor pack at some point in the past, then it could have arced through the connector when it failed. VERY common.. In the great list of things that stop blower motors, number 1 is resistor pack. Number 2 is the blower motor connector. You may be able to see discoloring on one or more of the connectors. Check each one for power. If you have the manual temp controls, then there are 7 terminals, and the voltage should vary (if I remember correctly) from about 5 to 12.5 volts on five of them.

If you get readings on all of them and there are no signs of burning, then check the blower motor as others have suggested. Easy to change, and as these vehicles age, and crap clogs the blower, they will need replacing some day. I did my connector plus blower motor all in an hour or so. If you need a new connector, they come with butt connectors to splice into the existing wiring, but I used proper soldering and heat shrink tubing to join the wires.

 

[6716]

I had the dash selector above zero (I forget which it was set to) and while I was trying to get the fan unit down, the fan turned on. I turned the selector back to 0, then back on, and it didn't work, then I jiggled the fan unit and it worked again, and then I moved it and it went off again.

Now I am back in the house because it is cold.

So it has to be the connection on one end or the other (or the line in between), right?

 

[Mooseman]

I've seen burnt connections at both ends. Check at power going into the resistor and at the motor.

 

[6716]

Well, I found that when I jiggle the harness that goes into the resistor, that affects whether the fan turns under power or not. I bought both a fan and a resistor pack. I plugged the new fan in and it didn't run either, that is when I started to jiggle other wires.

Now I just have to warm up and pull the resistor pack and look at the quality of that connection.

 

[6716]

I put in the new resistor and the fan just works, but here is the connector looking a little worse for wear.

The old resistor has corrosion on this pin but I couldn't get a good shot of it.

I suppose I could add some dielectric grease and maybe should have previously.

Do I want to install the new fan since I have it and the old one is out or do I return the fan?

 

[Mooseman]

Dielectric grease here won't help. Heat kills this connector. Best would be to get it out of the plastic holder, clean it, re-crimp the female pin part so that it holds onto the pin tighter and re-insert. Or replace the whole connector.

Up to you if you want to return the new motor but it's possible the old one was drawing more amps due to increased friction.

 

[6716]

Installed the new fan, put it all back together. Thanks for the tips.

 

[JayArr]

Is this the same as your connector?

More Information for GPD 1711755

www.rockauto.com

 

[6716]

Is this the same as your connector?

More Information for GPD 1711755

www.rockauto.com

That could be it. I'm not sure about the length of the wires and the individual connectors on the other end, though. I didn't look super deep into where and how those wires connected on the non-resistor side, it looked like they got wrapped together in tape and disappeared into the dash.

 

[JayArr]

Just cut and splice it in to get a connector that isn't damaged and corroded.

 

[KEEBZ489]

i had the same issue , i used some copper strands from #10 or#12 house wire. just a 1" piece folded over 3-4 times and wedged in , makes a tight connection again. my rear defroster plug was the same in the tailgate hatch

 

[Reprise]

Just cut and splice it in to get a connector that isn't damaged and corroded.

This. GM doesn't supply 'end to end' with replacement connectors; they give you a decent length of wire lead, and expect the tech (or you) to splice it into the existing harness.

 

[6716]

Apparently the wires ends may come out cleanly from the connector itself.

 

[6716]

Today I replaced the connector. 18 months ago when I replaced the motor and resistor pack, things worked well enough. Then last summer it didn't want to blow a few days after I got it back from a shop that took the dash out for the evaporator for a/c. I jiggled the wires behind the glove box and it fired up and I kept going.

Then it kept happening, but jiggling got it to work. Until today, when the jiggling magic no longer worked.

It was the ground wire connection that was fried. I wonder if I should check the actual ground itself, I have to go looking for it though. Lower right front of console or something like that.

Did you know that the red wire is hot even with the blower at 0 and the truck off? That must be what "hot at all times" means on the wiring diagram! Ask me how I learned that.

https://www.oreillyauto.com/detail/c/acdelco/lighting---electrical/connectors---terminals/blower-motor-connector/fd01c2f34085/acdelco-7-terminal-multi-purpose-wire-connector/acd0/pt2195/v/a/18319/automotive-suv-2005-chevrolet-trailblazer?q=blower+motor+connector&pos=2

The butt connectors aren't the best I suppose, but the panel hides them.

 

[Dr.Fiero]

Those fan motors (engines? cough... hahaha) draw a HUGE amount of current. My controller dropped dead when it was -35 so I *had to* bypass it until I could get a replacement.

Anyhow, with all that burning there, you've added resistance to an already high current circuit which (as you've noticed now!) creates a LOT of heat! And the more heat there is, the worse it'll get... it's a downward spiral.

And just thought I'd add that the module - is not a resistor pack! Yes, days gone by there was one. This is actually a big MOSFET, that's strapped to the heatsink you can see. The BCM essentially turns the fet on/off really fast (PWM) to control the speed of the fan. That's the reason you hear the fan ramp up and down. Not just go WHOOSH. I of course ripped mine apart when it died and semi reverse engineered it to fix it (just how I roll!). But it was taking too long and the cold was getting to me. So I just caved and bought a new one.

But at least I figured out how they work anyhow!

edit: That hot at all times wire is why sometimes these outright fail and you have no fan (fet dies open) or in my case, the fan was running ALL the time (fet dies shorted).