2003 TB LTZ Heater fan went strange and now doesn't run

[PatM]

A couple of weeks ago the air blower started acting strange. After starting the vehicle it would sometimes run very slowly but after restarting the engine once or twice would go back to normal. Around the same time the blower would sometimes not shut off until several minutes after the key was removed (removing key then restarting would sometimes rectify it).

As of yesterday the fan simply doesn't run at all regardless of what manual speed I set the fan too.

If it had been just intermittent failures to run I'd think it was the blower motor but the run-on after key removed has me thinking its a controls problem.

Anyone have any tips on how to diagnose where the problem really is?

 

[PatM]

Well I think I'm going to assume the resistor pack is the problem. The fuse is OK and the fan seems operational while the actual controls don't appear to fail (at least searches here always seem to point at the resistor pack rather than controller).

Fingers crossed!

 

[linneje]

Do you have the automatic climate control or manual?

The manual has a resistor pack. The automatic has a blower control module. My blower control went about 3 months ago, with similar behavior to what you have. It is not a difficult fix if you have a bit of time. Let me know if you need more info.

You have to know which you have before ordering the part.

 

[PatM]

The climate control version. I did see a few different modules available online as "resistor packs" but some were manual and some digital. I assumed the digital control was the one I wanted since its electronically controlled rather than a selector knob.

 

[Mounce]

Both manual and digital HVAC systems are dual climate control.

Does yours have an LCD screen with knobs to adjust temp or does it have sliders for temp and knobs for speed control/output area?

Knobs for temp with screen, digital.

Sliders for temp and no screen, manual.

 

[Mooseman]

Since he has an LTZ, I would assume he has the digital automatic system.

Sounds like a classic fan control module failure. It is basically the same as a resistor pack except it's electronic and controlled by the HVAC module.

 

[linneje]

I agree, sounds like the digital system, blower control module needed. I was surprised that you have to splice in the harness it comes with, but the instructions are included with the part.

 

[Mounce]

From my understanding they give you the new harness just in case you need it due to the harnesses being prone to melting and fusing to the module which requires the old harness to be cut off since you can't unplug it.

 

[PatM]

Yep, that is what is was. Installed a new one and everything is back to normal. I also discovered the outside air temp sensor is part of the module which seems kind of strange. I started the fan before re-mounting the module and the OAT shot up to 50C (only had it on for a couple of seconds.

So lesson learned, do NOT run the fan without the module installed. The outside air goes across the heat sink to keep it cool.

 

[PatM]

I agree, sounds like the digital system, blower control module needed. I was surprised that you have to splice in the harness it comes with, but the instructions are included with the part.

The old module used two connectors, one to control the module (3 pin) and the other running the fan (2 pin). The new design put all five wires into one connector. Easy enough to install. The power wires are #12 and the control wire is about #18 or perhaps #20 so two packs of butt connectors and you're done.