So I've only owned my beast for a couple of months and already it has required a little "TLC". A while back during a warm September day I took my boys to BR for some ice cream. On the way back home we all got a good whiff of something burning through the a/c vents. So I quickly got on the forum and proceeded to check my BMR.
Note:This is for informational purposes only and I do not hold any responsibility/accountability for your actions.


This is what I found

The orange wire got burned from an apparent loose connection and/or amount of surge current. IMHO the crimp style contact is not suitable for the current rating and it is evident that the problem was "fixed" with a white retaining clip so that the wires wouldn't wiggle and spark. It's located under the dash on passenger side, just remove the two screws and wiggle it out.


It even melted part of my harness connector !


Here is the old BMR in all its glory.


Here is the pinout for the BMR harness connector (this pinout will come in handy later).


Next, remove the white retaining clip at the connector by pulling it out (I just yanked on it with needle nose pliers).


Next, de-pin the connector by pushing/bending back the locking tabs with a small pick or screwdriver.


Next, reach for your new BMR and dremel tool to cut semi-around the housing just like in the picture. The reason for this is because I will SOLDER the wires onto this new BMR.


Next, I connected the wires via the original terminals individually onto the new BMR. Once attached, I soldered them in place and put electrical tape around each one. Afterwards I potted the wires with hot melt (glue gun) to create a 'backshell housing'. The melting point of this stuff is far beyond any temperatures that my cabin will face. (approx. 250ºF for those interested).


Finally, put that sucker back in and enjoy your brunt-free smell a/c (well almost burnt-free as it'll take a few days to clear out unless you spray Lysol in there or something)! I did take photos of the soldered wires prior to the hot melt but somehow they got deleted . Hope this helps someone out and it may even be applicable to other GM vehicles too.

 

Had the same problem with my 2008 H3. Purchased new resistor and wiring harness for about $85.00. Not hard to replace but had to remove the glove box. There should have been a recall for this problem because many H3 owners have had the same problem. When I picked up the parts at the dealer he said its not an uncommon problem. Next time ill do it your way and save the cash for something else. Thanks

 

Thank you for taking the time to post this useful information. KUDOS!

 

I'm hearing the fan go from off to abrupt quick higher speed (especially on 1 or 2) and once and a while a "buzz" sound I think from my blower fan. I wonder if I have the same issue with a lack of contact/burned wires. Have not smelled anything yet. Anyone else have this funky issue?

 

Got the dealership to replace it have an appointment for tomorrow. Would start and stop when I hit the brakes at a red light, then just went out. No smoke or smell.

 

Thanks for the info on soldering the wires, I did them all!


Cut back the white plastic so you can get at the tabs.
Sand paper and clean the tabs real good, be sure to tin all the tabs and ends of the wire and it will solder up real nice.
Draw up a little schematic as to where the colors go, I marked them with a sharpie before un plugging the resistor from the harness.


here's some pictures.

 

If that one terminal has been getting hot enough to melt the plastic, will that same heat possibly melt the solder and disconnect?

 

The melting is caused by heat which is caused by a loose connection, which is the connector slid on to the resistor tab.
By soldering them they are a solid connection no way to be loose to cause the heat.
Loose electrical connections cause heat. It does not cause an over current situation which would blow a fuse or circuit breaker.
The heat will continue until it burns, or corrodes the connection to a point of opening the circuit. (in this case the blower stops working)

 

I’m not suggesting an overcurrent situation. But high current can generate heat without reaching a level that will blow the fuse. I work for a major utility in SoCal; our lines get very hot during periods of peak load, even without reaching current levels that would trigger overcurrent devices (fuses, breakers, fusible links). Current = heat. Also, resistors, by their very nature, generate heat, and some of that heat will also be drawn into the connected wiring. I would guess that the blower motor resistor assembly is manufactured with special high heat solder; solder that most of us DIYers would not have on our workbench.

Consider: All 5 terminals within that connector are the same, yet only the one on the end is heating up and melting the surrounding plastic. Why? The answer is 3 things: High current in that particular wire/terminal, heat from the resistor itself, and finally, the bad connection. Fixing the connection is enough to solve the problem, but rest assured that the other 2 conditions still exist (by design) and there will still be at least some heat in that whole assembly.

Although I haven’t yet had the problem (that I’m aware of; maybe I should pull it and take a look?), it’s about time that Chevy is finally going to address something that so many owners have struggled with for so long. It’s also great that through forums like this, we can all gain knowledge of our trucks and help each other out. Kudos to all that have fixed this and shared the details of the fix. Really curious as to what Chevy’s “official” fix will entail.

 

I just want to elaborate on the subject a little bit.

jonnieh3 is correct regarding the reason for melting. The main reason the wiring gets this hot is due to a weak connection. A weak connection that causes intermittent circuit performance which leads to sparks. Very similar to the properties of an arc welder, if you will.

Large enough loads do generate heat as well which 650Hawk mentioned. However, the reason certain fuses don't blow is simply because it hasn't reached the threshold of current conduction and its specified temp range. This is why it is important to use the correct fuse per the circuit load. Otherwise you'll burn components and not fuses.

Current = Voltage/Resistance (Ohm's law for those interested), therefore heat is not a factor but a by product. However, when conductors get hot their resistance increase which causes an additional load. This is where cooled super-conductors come into play (we'll cover that next time ).

The heat produced by this circuit is not enough to melt the solder let alone sustain the amount of time needed to melt (assuming soft lead solder which has a melting point of 374°F, even higher for lead-free solder). If that were the case, everyone's bmr/wiring harness would melt almost instantly and blow the fuse the first time it is used. In fact the insulation would burn first rather then the solder joint. What does confuse me is the 30-amp fuse that is in there . Most older European cars that share a similar circuit (voltage divider circuit) use screw terminals instead. This of course is a more costly manufacturing process and who wants that, definitely not bean counters.

Newer systems employ the use of a PWM signal instead. I'm also curious as to what the new "fix" consists of. I'll wait on the feedback from other members who will have the recall performed.