Hey guys I'm looking for some answers to an issue I've had for a while now. My fan/blower stopped working when I replaced the actuator for the temperature control that switches doors from AC to Heat . After replacing this actuator I turned key to on and the module went into recalibration and went through all the blend doors and finally the two ***** stopped flashing and I checked to visually see that the actuator was working and it was . At that moment I look at fan **** and it was on 2 so fan should be on but wasn't . After going through all speeds I realized something changed after actuator replacement as the fan was working up to my installing the actuator and I was using the fan as it was hot outside and control **** had it stuck between heat and AC so I was running fan to cool the inside a little .I don't know why the module did this automatic recalibration as my shop manual tells how to do that and ***** have to be in a certain position and then you press first and third **** and hold till they start flashing with fan on high. Well none of those ***** were in right position. I started trying to figure it out and verified the fan was working fine by running battery power to it . Verified relay was working and verified that resistor was good also . Took module out and found that it only had 5 volts to it at all times and manual says the PCM gives fan the ground when the **** is turned to fan on. The 5 volts runs the actuators and positive battery is always there and PCM adds ground to complete circuit . I confirmed that the 30 amp fuse in fuse box has power at key on and both sides of fuse telling me the power is always there at key on. I ended up with other issues as I played with the fan issue over the next few months . I have a 2020 GMC 3500 Sierra that I drive and Hummer I was selling so was not in hurry. Turned out the fuse box had corrosion down in the five layers of grinds of the fuse box . I took it apart and cleaned everthing and put dielectric gress on all of grids and connection points. Also checked and cleaned the two wiring harness connectors in bottom and checked every wire for any possible break or sign of issue . After that all issues but the fan were solved . I did not have PCM pinout and tried everything to buy or get one to no avail. I took Hummer to a shop and asked them 7 times to have tech call me before he starts his diagnostic as that was all I wanted them to do and I would fix it. I figured they had PCM pinout. Three months later after calls asking for tech to call first I find out that they finished diagnostic and they say its the fuse box after they applied artificial power by passing fuse box and PCM control of ground . I ask them to explain that as I know nothing is broke inside box so how could it be issue plus you gave the ground that PCM controls which is where I think the problem lies . And for $433 I ask you to back your diagnostic and they refuse. Fuse box is $300 and if I pay them $433 and go by that diagnostic and they are wrong then I've $800. Can anyone confirm that without checking the PCM control of ground you can't come to this conclusion. I have two shop manuals and bought second one just to get PCM pinout and guy said it had it and he lied. Both manuals have every other pinout for every connector but PCM three connectors. GMC should be ashamed of this behavior . I can't find or buy one anywhere , I have tried for months. Thanks and hope nobody has this issue as it is making me pull my hair out . If you know where to get pin out please let me know.

 

So, let me get this straight, you already tore apart the fuse box and thoroughly cleaned it? By the sounds of this lengthy writing that you've covered a lot of ch!t!

 

Disconnect the battery, negative first. Wait 10 seconds or more. Reconnect battery positive first.

 

What year is your H3?
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Hummer H3 – Wiring 2006
Hummer H3 – Wiring 2007
Hummer H3 – Wiring 2008
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The PCM is not involved in the operation of the blower motor. The only tie between PCM and HVAC system is to energize the AC clutch.

The blower motor operation works the old fashioned way, controlling the desired fan speed by turning the fan speed rotary switch which provides a hard wire connections between ground and the high speed relay and/or ballast resistor. There is no computer interface involved in this circuitry.

Since the blower motor is not working in any position, and the HVAC controller itself is working, the following are the likely causes:
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• The HVAC control module connector C1 is disconnected/not fully seated (most likely reason since the problem started when you did work in this area)
• The 30A Blower Fuse (82) has failed/blown (unlikely since you already checked it)
• Blower motor resister assembly internal fuse has failed/blown (check for continuity between pin A and the other pins - each pin should have a different resistance reading, none should be open)
• The blower motor ground (G106) at the right inner front wheel well behind the battery is disconnected OR the ground wire to the HVAC controller and fan high speed relay has been broken/cut somewhere in the harness under the instrument panel (check for continuity between the HVAC controller connector C1 pin 5 and ground AND also check between the blower motor relay pin 1 and ground. Its unlikely to be G106 since many other systems are on this ground and wouldn't be working if that was the problem)
• The HVAC control module blower motor switch has failed internally and is stuck in the off position (extremely unlikely)

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The only way this could be something internal to the fuse box would be if the HVAC relay and HVAC blower fuse both test ok, and there is still no power coming from the fuse box (power would be at connector X1 pin 47 but that's buried under the box - you can check this by looking instead for power at the blower motor pin 2 (brown wire) or the blower motor high speed relay pin 2 (also a brown wire)). If you didn't disassemble the fuse box before the problem started, and the fan was working before you changed the actuator but not immediately afterwards, its extremely unlikely that a problem spontaneously appeared in the fuse box because of the actuator change).

Here are the wiring diagrams from the 2006 H3. Other years have the same wiring for the fan operation, but have different HVAC controller pin out for the computer controlled stuff)