Burnt fan control switch

[chatterx]

Putting together the audio system today and figured I would take a look at the Heat/AC control unit to see why the a/c only works when I smack the unit sometimes and also to see why the fan control was so quirky at times. I knew the back of the plug for the fan control got pretty warm at times cause I could reach my hand in there and feel it as I have had the stereo out for a few months while I installed new door speakers and was adding a layer of second skin to the vehicle.

The control unit has been acting quirky for about 3 or so years now. Once I took it out I was amazed I didnt burn down my vehicle lol.

Attached are the pics of the fan control knob and its plug in. The whole knob just fell apart and the grease thats inside it has been cooked. The AC cutting out and working when I hit the unit can be attributed to a wire that came unsoldered and was barely touching two resistors inside the unit. It was coming off of one of the little blue covered bulbs inside.

Im just wondering if that wire touching caused that knob to burn out too? I highly doubt it. Can these knobs go bad? Is this a sign its bad? Can I reuse that plug when my new HVAC control unit arrives?

 

[Sparky]

Um, wow.

I'd be replacing that harness plug. It's cooked.

 

[chatterx]

question is where do I acquire the plug

 

[chatterx]

ouch I found one but its 30 bucks

 

[Sparky]

Chop one off a pick-n-pull maybe

 

[hockeyman]

ouch I found one but its 30 bucks

Not sure what your deductible is, but $30 doesn't sound so bad -to me.

Seeing that, I'd probably go as far to bypass and run a whole new (& slightly larger) fused power wire to that a/c control plug. Something about seeing my vehicle on fire that just doesn't sit well with me...

 

[Mooseman]

You also need to check all the wiring, including to the fan motor. That could have been caused by high resistance from a bad connection increasing current.

 

[Sparky]

Ahem *puts on electrical engineer hat*

Increased resistance in a circuit reduces current. I = V / R, if you increase R you lower I

What resistance can and does do is increase heat, which is why a bad connection can burn up like that.

Shorted coils in the blower motor can lower the overall resistance of the blower, which would increase the blower's current draw, that could burn up stuff. But, I'd like to think that GM would fuse things properly to avoid burnt wiring from overloads like that. Maybe I'm just being wishful

 

[Mooseman]

What he said

 

[AtlWrk]

But, I'd like to think that GM would fuse things properly to avoid burnt wiring from overloads like that. Maybe I'm just being wishful

Wishful indeed: the HVAC terminal shown is rated for 25 amps. The fuse for those circuits is...wait for it...30amps.


EDIT: In case you were wondering: the blower motor resistor connector is rated for 30 amps, fused at 40amps.

 

[chatterx]

I ordered a new plug from rock auto. also have a new control unit on the way. I will use the unit out side of the dash for a bit to see if it gets hot again.

Also I dont know if this is anything but the #5 fan speed on my unit went out. I can use all other speeds but 5 cuts out the blower

 

[Mooseman]

Could be the relay in the resistor pack or the connection to/from it.

 

[chatterx]

I did a little reading on that issue and I am seeing it can be two things. A resistor or a fuse under the hood. Apparently #5 fan setting has its own fuse. I will have to investigate this in the morning when I get off of work. I believe this may have had something to do with the burnt plug and all.

 

[AtlWrk]

I strongly urge you to at least test (if not outright replace) your blower motor.

It's not unusual for resistors to burn their connectors--it's a known weak link since that connector has to handle the highest current. If that was your only symptom then we could chalk it up to "it happens." However, it is highly unusual to see the damage to the HVAC connector to the extent you have.

I would hate to see you replace everything only to have it all destroyed again because of a bad blower motor.

 

[chatterx]

Ok just an update here. My new plug came in as well as my HVAC control unit. I havent put the new plug on yet but will this weekend when off.

I did plug the unit in and the plugin on the back of the unit does start to get hot. will see if it still does after the new plug. I am thinking a blower motor replacement is in order. I forgot to mention that even with the unit unhooked or when it was hooked up and not set to blow air I can hear what sounds like a squeaky wheel coming from the inside of my dash. I am willing to bet the bearings on the motor are shot causing a high draw.

 

[Tiggerr]

The blower draw probably caused the other issues....
I'd always recommend replacing it if your resistor goes out too...
An ounce of prevention and all that crap lol

 

[chatterx]

Im going to get a blower and resistor pack with a new harness. Might as well its only like another 50 bucks for that all. Is this a hard job to do?

What happens when the resistor goes out

 

[Tiggerr]

Im going to get a blower and resistor pack with a new harness. Might as well its only like another 50 bucks for that all. Is this a hard job to do?

No not really 3 wires..the resistor is about $30 for climate control not sure for manual control...
I used an AC Delco blower motor though.. not sure if any of the cheap ones are worth a damn... I got lucky and found one on fleabay for like $50... usually they're around $100... YMMV...

 

[chatterx]

the resistor is like 16 bucks for a manual control it looks like. as for the blower 100 bucks is the cheapest for a delco on ebay.

 

[Tiggerr]

the resistor is like 16 bucks for a manual control it looks like. as for the blower 100 bucks is the cheapest for a delco on ebay.

Yeah I got lucky when I found one discounted... maybe someone else can chime in on a good brand... could check NAPA too they're never cheap but I care more about quality and doing he job once... when possible

You'll realize how weak your old one was too once you replace it... mine will blow you out the damn door now... lol

 

[chatterx]

Im doing research on the TYC model rock auro offers for 38. Its either that one or the delco its looking like. TYC offers two different ones though. One says first design and its 36 bucks while the second one is 45.

 

[Tiggerr]

Im doing research on the TYC model rock auro offers for 38. Its either that one or the delco its looking like. TYC offers two different ones though. One says first design and its 36 bucks while the second one is 45.

I know my new one was a bit different than the old one.. the vent tube and motor cover were all together in one piece.. unlike the original... that may be the 2nd design deal