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03 Rear heat - *nothing* happens !

03 rear heat nothing happens

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#1 OFFLINE   Celerity

 
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Posted 28 August 2017 - 06:34 PM

Hey All !

 

I'm looking into this new Suburban that I picked up. The heat controls are the auto controls with the digital panel built into the back. (LT luxury group3)

 

The control panels are dead. Well, the rear one activates and says it will do stuff - but nothing happens. No vents, no fan, no temperature door actuation.  So from the front or rear panel - it doesn't do anything.

 

I took apart the back and have continuous voltage to the fan motor. (WTF?)  Like the moment the key is "ON" I have 12 volts to the motor. The motor does nothing. The motor seems to spin alright and the brushes are in good condition.   The unit before the fan (The resistor box I presume) has permanent power to it, but the "input" line in the middle is dead. Nothing ever. No matter the fan setting, that has no voltage at all.

 

Fuses in the cabin and underhood checked and in good working order. When I pull those fuses I get no power to the center console logicon.

 

The connector behind the kick panel on the Driver's side is good, but there is no voltage at all going through it. I have no idea what that plug is but some guy on youtube recommended checking it for burns (Nothing I've seen so far is burned)

 

With the power on I get no activity whatsoever from the entire rear unit. It's just dead to the world.

 

Any ideas ?



#2 OFFLINE   AA1PR

 
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Posted 30 August 2017 - 08:17 PM

I'm not sure if the heater blower motor resistor assembly located underneath the passengers dash has any impact on that

that was my problem but only affected the front 2 sides

 

let me ask,  you have rear voltage and you can get the fans to engage? there must be a blower motor resistor module for that too is my guess

 

if the fans turn I'd say look at the passengers side of the water pump, there is a black plastic electronic assembly that divides coolant to the front & rear, these go bad and are a common problem

 

just googlefu'd and found this, hopefully it helps ~ http://sparkys-answe...lower-will.html

 

however this video shows otherwise ~ maybe the one you mentioned

 

& this longer one as well ~


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2004 GMC Yukon, 4X4 SLT, 5.3L Vortec, ~ Yukon Build Thread
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1966 Stevens M416 trailer too ~ M416 Build thread

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#3 OFFLINE   Celerity

 
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Posted 30 August 2017 - 10:25 PM

Yup ! Got both of those videos and the supporting threads that spawned them. The orange wire thing is very prevalent on this chassis.

 

Front units are ok. Here is an update:

 

The rear *APPEARS* to have a ground-switching resistor pack. You know how the knob turns up incrementally ?  It doesn't just go "1,2,3,4"  It turns up like a volume knob. And the digital one also doesn't use 3 resistors. And the AUTO mode certainly doesn't. There is a processor in there.

 

But there is still a resistor pack.. only it doesn't really work like the traditional logicons.  The "Volume" of the fan may be set through the ground.

 

The purple wire is always getting full voltage (Funny, it gets exactly 14.4 volts which tells me there is a GREAT connection between there and the battery. Good stuff.) The black wire is ground. It's labelled that way, and it meters out that way too.  So what I'm going to do is short the ground to the chassis and I should see the fan spin. 

 

The fan itself is a serviceable unit. I can open it and inspect it but the rear cover is also the bearing so I can't operate it without the cover.  But brushes look great, the windings test out fine and everything looks great. 

 

I actually ran out of time because I killed the battery and  now it won't hold a charge at all. Since I get paid once a month and today is the 11th hour of my hand-to-mouth subsistence living I'll have to wait a bit before this goes full steam again.

 

I did find enough quarters in my couch to get my new bearings for the front wheels. I'll try to put those in ASAP and just work on the heat thing later.

 

PS that first video .. the connector is neat but whoever is following that direction needs to first get experience with connectors. Because you can easily futz up your truck and start a fire if you don't do that stuff right.



#4 OFFLINE   Celerity

 
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Posted 30 August 2017 - 10:28 PM

Oh, I forgot that I was going to clarify the possible ground-switching unit.  

 

Since this is a volume knob style of operation, my dad (An electronics wiz) has pointed out that under that condition it is likely not lining up resistors and then making a switch to choose which resistor you're going to use. Instead, it is creating square-wave modulations to control the motor speed.  This means diodes and stuff. So the resistor pack isn't really just a bunch of resistors like the front unit may be, or like the "1,2,3,4" speed fan units are.



#5 OFFLINE   AA1PR

 
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Posted 31 August 2017 - 05:41 PM

Oh, I forgot that I was going to clarify the possible ground-switching unit.  

 

Since this is a volume knob style of operation, my dad (An electronics wiz) has pointed out that under that condition it is likely not lining up resistors and then making a switch to choose which resistor you're going to use. Instead, it is creating square-wave modulations to control the motor speed.  This means diodes and stuff. So the resistor pack isn't really just a bunch of resistors like the front unit may be, or like the "1,2,3,4" speed fan units are.

 

yes, the video can lead someone into SH%$

 

yes, the knob is actually a potentiometer aka variable resistor in essence that tells the blower motor resistor module in the rear how much voltage there is and responds accordingly

 

humbly I would look at that unit since all fingers point to it

 

you have voltage but no fan, this is what controls the voltage on not sure what color wire to engage

 

good luck with those quarters, I'm disabled and know the feeling all to well


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2004 GMC Yukon, 4X4 SLT, 5.3L Vortec, ~ Yukon Build Thread
Trail Master 2.5" leveling keys, SkyJacker  Hydro 7000's & MOOG 81069 rear coils with 1.5" spacers,
Hella 700FF's,  Running on 33's BFG TA KO & XRC 12K Comp Winch

1966 Stevens M416 trailer too ~ M416 Build thread

"Now she is gone I got my Yukon"   

ExpeditionNorth.com


#6 OFFLINE   Celerity

 
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Posted 02 September 2017 - 01:51 PM

I jumped the ground over to the chassis, and the motor hums like an angel singing at sunrise. 

 

So I suppose this is the resistor pack at this point ?   

 

I have no workbench setup anymore (Wife's business TOOK OVER THE HOUSE) so I'll have to dig out my bench equipment to test it.  I also have to take it apart and it's a sealed unit so I'm not sure if I should or not.

 

Next I'm dragging the meter through the interior to check every part of the circuit. But I still have no schematic or wiring diagram for it.   Anyone here have the haynes manual or anything ?



#7 OFFLINE   AA1PR

 
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Posted 02 September 2017 - 09:22 PM

I jumped the ground over to the chassis, and the motor hums like an angel singing at sunrise. 

 

So I suppose this is the resistor pack at this point ?   

 

I have no workbench setup anymore (Wife's business TOOK OVER THE HOUSE) so I'll have to dig out my bench equipment to test it.  I also have to take it apart and it's a sealed unit so I'm not sure if I should or not.

 

Next I'm dragging the meter through the interior to check every part of the circuit. But I still have no schematic or wiring diagram for it.   Anyone here have the haynes manual or anything ?

 

I thought about rebuilding my old one (front) and decided it wasnt worth the aggravation since I needed a fan for the 20 mile ride home that sub zero winter day

but you might have more time to try it

all these electronics make me wish I had an old pre-96 vehicle still

times were simpler, spark, fuel, air...


___________________________________________________________

                           

 

2004 GMC Yukon, 4X4 SLT, 5.3L Vortec, ~ Yukon Build Thread
Trail Master 2.5" leveling keys, SkyJacker  Hydro 7000's & MOOG 81069 rear coils with 1.5" spacers,
Hella 700FF's,  Running on 33's BFG TA KO & XRC 12K Comp Winch

1966 Stevens M416 trailer too ~ M416 Build thread

"Now she is gone I got my Yukon"   

ExpeditionNorth.com


#8 OFFLINE   Celerity

 
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Posted 05 September 2017 - 10:48 AM

 

all these electronics make me wish I had an old pre-96 vehicle still

times were simpler, spark, fuel, air...

 

...  $1.10 for a gallon of gas... less than 5% MTBE / gal ... Oh yeah the good ol' days !   Those engines are getting 5mpg these days not because of what they are or what they are pulling (an old square body weighs as much as my econo BMW did... let that sink in) but because the gas is total garbage now.

 

Where are our 100mpg cars ? We're driving them. We're also driving them on what can barely be considered "octane"  (seriously, they cheat. It's barely 8 carbon moles per volume)



#9 OFFLINE   Celerity

 
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Posted 05 September 2017 - 10:57 AM

I am a pro with the Toyota 22R/20R/RE engines. I've built more than 100 of them, and I know them inside and out every mm.

 

in highschool, from 1992 to 1994 I drove a 1979 20R powered Celica.  between 1992 and 2004 I owned more than 20 RWD Celicas and trucks with the 20R engine.

 

Between 92 and 96 every fill up cost $19 (16 gallon tank) and I got 25mpg without variance.  I drove more than 40,000 miles a year.

 

I started getting less than 20mpg from 97-02 on that engine. But luckily I had a few test engines and platforms. I was getting the same mpg in the same style of Celica with a fuel injected 22RE and the 22R. I had a 20R/22R hybrid Celica as well that got somewhat better economy if I drove it the same (high compression, fun transmission.. yeah I drove it a little harder than the others) and my trucks were the same - a Cali choked truck, a 48 state truck, a high-altitude 4Runner and a 48 state 4Runner.

 

It was the same for ALL of them, simultaneously. After 97 they all started to get worse and worse mpg.  Carefully analysing engine tolerances and rebuild status, weights and chassis mods. The gas is getting much, much worse.

 

Then I got a job at a petro-chemical company (shall remained unnamed) and talked to their engineers and chemists. I saw some shocking documents and regulations that would make the american public take to the streets with pitchforks  and torches.   The gasoline is totally watered down, per government regulation.







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