Jump to content

03 Suburban rear HVAC not working

Celerity
 Share

Recommended Posts

Celerity Enthusiast

Celerity

Posted
Posted

Hey all !

 

Just signed up, but I'm coming over from gmc4x4.com. That forum has pretty much died out, and I need some pretty urgent help.

 

Rear heat !  Fan doesn't spin. Doesn't get voltage at the fan.  I have done the following, but I am willing to double check things too:

 

  • That red wire under the dash. Complete, charged and seems to be ok. I really don't understand this fix, so I'd be willing to talk about it some more.
  • Replaced rear resistor with the new updated one. Millivolts on those wires - nothing else.
  • Fuses checked and appear to be ok.
  • I have the auto-thermostat model with rear and fore temperature settings and "Auto" fan speeds. When I move the front HVAC control, it will disable the rear (Unless it's in AUX and the rear comes to life)
  • The vent flapper doesn't appear to move either.  It's like the entire rear unit has just gone to sleep.
  • Voltage applied directly to the motor will spin it. Motor and windings appear ok and test out ok.

 

Does anyone have any ideas ?

  • Replies 35
  • Created
  • Last Reply

Top Posters In This Topic

Popular Days

Top Posters In This Topic

Popular Days

Popular Posts

carnau
carnau

I have run into a lot of Control Processors causing this issue. If it doesn't work nothing will. Here is the Schematic. Check the Power coming into the Processor on circuit 1740 and the Ground on 1450

Posted Images

SpartanAutoworx Enthusiast

SpartanAutoworx

Posted
Posted

Check for voltage on the left rear pillar should have one connector with 4 wires. Two of them should be orange in that connector of a pretty good gauge wire. I bet you have voltage to only one of the orange wires.

carnau Enthusiast

carnau

Posted
Posted

I have run into a lot of Control Processors causing this issue. If it doesn't work nothing will. Here is the Schematic. Check the Power coming into the Processor on circuit 1740 and the Ground on 1450. If you got power and ground check the Power and ground from it to the blower motor. If you have power coming to the Processor and nothing coming out. That's the problem.

 

Part Number - 15-73506

http://amzn.to/2i2vhCb

 

Don't forget to hit the Like button if this helps!

879570.gif

  • Like 1
Celerity Enthusiast

Celerity

Posted
  • Author
Posted
55 minutes ago, SpartanAutoworx said:

Check for voltage on the left rear pillar should have one connector with 4 wires. Two of them should be orange in that connector of a pretty good gauge wire. I bet you have voltage to only one of the orange wires.

Wait, which left ?  On the side of the HVAC unit ?  I only know of one Orange wire, and that surely has very little voltage on it. like 300 mv.  But I'm not aware of the other one you're talking about. 

 

So yeah, you're already correct. One of them doesn't have voltage. Now what ?

Celerity Enthusiast

Celerity

Posted
  • Author
Posted
26 minutes ago, carnau said:

I have run into a lot of Control Processors causing this issue. If it doesn't work nothing will. Here is the Schematic. Check the Power coming into the Processor on circuit 1740 and the Ground on 1450. If you got power and ground check the Power and ground from it to the blower motor. If you have power coming to the Processor and nothing coming out. That's the problem.

 

Part Number - 15-73506

http://amzn.to/2i2vhCb

 

Don't forget to hit the Like button if this helps!

 

Now this is pretty good stuff.. that schematic though.  Where did you find that, the Necromonicon or the Darkhold ?  That thing is so hard to understand !  I'll look for the unit itself and just measure some voltage.   Tonight, however, is some kind of record breaking McMurdo station cold out there.  I'll give this a run in the morning. Thanks for the amazon link too !

SpartanAutoworx Enthusiast

SpartanAutoworx

Posted
Posted
2 hours ago, Celerity said:

Wait, which left ?  On the side of the HVAC unit ?  I only know of one Orange wire, and that surely has very little voltage on it. like 300 mv.  But I'm not aware of the other one you're talking about. 

 

So yeah, you're already correct. One of them doesn't have voltage. Now what ?

 Right side of vehicle   Passenger side  

 

 I'm used to customers always thinking it's  looking through the window. 

 

 So passenger-side the right side  four pin connector with two orange wires. 

Celerity Enthusiast

Celerity

Posted
  • Author
Posted
On 11/10/2017 at 9:17 PM, SpartanAutoworx said:

 Right side of vehicle   Passenger side  

 

 I'm used to customers always thinking it's  looking through the window. 

 

 So passenger-side the right side  four pin connector with two orange wires. 

Alright, so it appears the large orange wire isn't getting voltage. The other one is - Which is kinda what I was saying. That large orange wire is the supply for the resistor.

 

The smaller orange wire - What is it ?  Where does it go ?  What's next ?

Celerity Enthusiast

Celerity

Posted
  • Author
Posted
On 11/10/2017 at 6:08 PM, carnau said:

I have run into a lot of Control Processors causing this issue. If it doesn't work nothing will. Here is the Schematic. Check the Power coming into the Processor on circuit 1740 and the Ground on 1450. If you got power and ground check the Power and ground from it to the blower motor. If you have power coming to the Processor and nothing coming out. That's the problem.

 

Part Number - 15-73506

http://amzn.to/2i2vhCb

 

Don't forget to hit the Like button if this helps!

 

Ok, I have power going in, but the orange wire on the output (grey) connector is giving me 2.67 volts regardless of knob position.

 

sound about right ?

Celerity Enthusiast

Celerity

Posted
  • Author
Posted

Looks like the input voltages on the input side are there, but the output side is running ~3 volts. But on the orange cable to the fan resistor I get 0. 

 

Still not sure how this box works. The rear panel stops operating (Says "OFF) when I disconnect the module. The voltages don't change with the knob (But I don't think it should)

 

 

carnau Enthusiast

carnau

Posted
Posted

It should only be a 3 wire connector. Black , Purple, Orange. The orange wire should have Battery voltage. Does it have battery voltage? Not on the resistor. On the processor.  

Celerity Enthusiast

Celerity

Posted
  • Author
Posted
6 minutes ago, carnau said:

It should only be a 3 wire connector. Black , Purple, Orange. The orange wire should have Battery voltage. Does it have battery voltage? Not on the resistor. On the processor.  

Yeah that one there is dead.  I get millivolts on the purple and orange, the black is ground and is continuous to ground.   This is the problem.  It's dead.

carnau Enthusiast

carnau

Posted
Posted (edited)

Well the Next step would be to check the RR HVAC Fuse Under the hood. It is a 30amp fuse. See if it is good.

Edited by carnau
Celerity Enthusiast

Celerity

Posted
  • Author
Posted

Done and Done. Fuses are all ok. I'm getting power to the hots on the control module, and I am getting voltage on the orange under the dash.

 

Next is why I'm not getting voltage on the wire - which if I'm to understand that Darkhold schematic, that should be hot all the time .. like it's the same wire. 

 

But I get power to the control module, and then I get nothing but 3-4 volts FROM the control module at all times.  So I am getting on the side that the control module is bad.  But I'm still not sure. I think after this there is nothing left to replace.

 

If that orange truly is dead, then the control module shouldn't work either.... Right ?

SpartanAutoworx Enthusiast

SpartanAutoworx

Posted
Posted
4 hours ago, Celerity said:

Alright, so it appears the large orange wire isn't getting voltage. The other one is - Which is kinda what I was saying. That large orange wire is the supply for the resistor.

 

The smaller orange wire - What is it ?  Where does it go ?  What's next ?

Look up the connector for c397

The two orange wires should have 12volt battery positive voltage

If that other wire is dead I would say you need to trace it back for a break in the wire. 

I bet you put 12volts to the wire you will be back in business.

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing

  • Latest Articles

  • Posts

    • Grumpy Bear
      OCI, not when but why?

      By Grumpy Bear · Posted

      That dog don't hunt. 😏   First, a 2025 with 12K on the clock AND idled for a year nonstop is false on it's face; this is 2026. You can do one or the other but not both.    Second, ENGINE HOURS are absolutely available. The rest is third grade math. Micky Mouse scanner he got out of a box of Cracker Jacks OR an ID10T error.    Third, if they ran it out of oil "Several times" that motor is boned on the first hit.    Does this guy think piling higher makes it stink less? 
    • Chuck FB
      OCI, not when but why?

      By Chuck FB · Posted

      That's interesting, I assume that would add to the cost of the oil but also I was forgetting to bring up the issue of the low tension rings allowing more oil past which in turn forces the cats to have more oil additives pass through them that wouldn't otherwise so they are creating that problem and of course its all in the name of fuel economy. Mind you the other issue would be the lack of additives that fight the formation of carbon within the piston ring grooves which turn the engine into an oil burner and with in this GM forums case is your average off the shelf Dexos licensed oil, meanwhile the other off the shelf oil being Valvoline's R&P isn't licensed and the only one that is which is that certain Mobil oil that came out recently ( its not even being marketed in Canada ) and only a fraction of vehicle owners are going to be using it out of all the other oils on the shelf or the quickie lube bay that meet the Dexos spec by way of actual licensing.    Also I suspect that its an easy excuse to pool the non turbo DI engines in with the turbo DI engines and design the oil to not have LSPI issues in the most demanding engines and short change the naturally aspirated DI by not offering a higher concentration of additive package they could handle and still not be at risk of LSPI.    I wonder if Amsoil flipped the switch just lately and did whatever packaging designation at the same time as I wonder what oil formulation I would have bought in May, of course I don't know when it was packaged at the factory vs how long it was in storage at the Edmonton warehouse. I know its been said at least in the past that the big players switch over to a reformulated oil but the packaging has not changed until they make that move as well so there is that cross over time where its a new formulation in a predated formula marked package. 
    • PunchT37
      OCI, not when but why?

      By PunchT37 · Posted

      Hmm. A real reason to not just use the odometer to determine OCI?    
    • Grumpy Bear
      OCI, not when but why?

      By Grumpy Bear · Posted

      Sad thing is that this doesn't have to be the case. LSPI can be solved without a reduction in TBN. Swap Ca for Mg.  Cats are not a issue if the OEM can get a ring and valve guide seal even at SN levels of SAPS. Dizzy is purring like a kitten with a bowl of warm milk. 200K of Full SAPS oil and zero detonation issues and nice a clean inside and out. This shouldn't be an issue. It isn't 1920.    Tell ya what AMSOIL SS is excellent at, internal cleanliness. The new formula is even a step up from their already outstanding cleanliness levels. Can't say the OEM offering is quite that clean. There marketing suggest the SS is cleaner.     That is the only defense with at shelf oil. Nothing wrong with them if you ignore the marketing and OEM 'recommended' OCI and use a thimble full of common sense. 😉 You go sir. 
    • StingerZ16
      Roll up bed cover experiences

      By StingerZ16 · Posted

      I started with a folding cover by BAK PAC on my 2500. It went bad after close to 5 years. Bent and vinyl coming loose. Contacted BAK and they gave me a very good discount on a Revolver. Had it a number of years. Mostly outdoor storage. Some garage storage. Vinyl started to come loose. Still under warranty so they replaced to cover. Sold the 2500, bought the 1500 and got another revolver for it. Had it a couple years now and no issues. I store it indoors. Got a bit of discount when buying it as well. If you are seeing problems, contact BAK or real truck and let them know. Customer service was pretty good. But I think they changed their warranty.

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...