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GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 29570
Experience:  GM Grand Master Technician 2007. 14 years experience.
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Chevy 1500 Suburban: 2000 Chevy Suburban. Rear Blower system

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2000 Chevy Suburban. Rear Blower system stop working. Tested motor with DC 10V and 14 volts and operates fine. Tested volts going into Blower motor control module/resistor and read 14v from black/red and 10v from red/pruple. Also tested power coming out of Module/resistor leading to blower and red "2v" Red/Black going to blower. I bought a new Module/resistor (Delco P/N 15-8794) and installed and still no blower. New module/resistor still reads 2.3v.

What am I missing?
Hi, is this automatic climate control or manual? Also does it have a sunroof. Let me know and i will try to help you out. Thanks, Eric
Customer: replied 5 years ago.
Yes, Automatic Climate control. No, Sunroof. Also have replaced the fuses underhod Hvac and indide driver door. although, nothing looked wrong about them.
What is the voltage on the brown wire going to the rear blower module? Also what is voltage between black wire at blower and orange wire at blower?
Customer: replied 5 years ago.
Only three wires going to rear blower module orange, purple, black. Org/blk volt is 14.3v and Blk/purple is 00.4v, and Org/purple is 9.8v wires from module to blower are red and Black and they record 1v. but this is NEW.... they read 1v whether i have wires going to module plugged in or not.
Ok, check between purple wire and black wire. Turn blower speed control slowly from low to high speed and see what the voltage does.
Customer: replied 5 years ago.
off position purple/black read 4v. turning control slowly from low to high makes reading drop to 3.4v. and returns to 4v when back to off position.
Ok, does it have a blower switch for the rear on the front dash and in the rear of the vehicle or just on the dash?
Customer: replied 5 years ago.
both front and rear.
Ok, some of my schematics are not matching up with some of the wire colors you have. Can you give me the VIN number so i can make sure we are on the same page. Thanks, Eric
Customer: replied 5 years ago.
VIN 3GNEC16T5YG124235Can you tell me what the voltage is supposed to be coming out of module to fan? What is minimum required?Also wanted to mention that the system has three control board. One in dash controls front controls (driver/passenger), then there is a control on the front headliner that allows driver to direct system to rear, and the third control is located in second row headliner and permits 2nd row passengers to manage temps/speed, etc. All controls also Auto Climate.

Sorry for the delay, my internet has been acting up today. Is this the part you have replaced in the rear?graphic

Also if you check at blower plug the voltage should be 12volts on high speed and decrease down from there on the lower speeds, I cant access my info at the moment but see what your readings are from low to high at the motor connector unplugged. Thanks, Eric

Customer: replied 5 years ago.
that's not the part. My part is AC DELCO P/N 15-8794. You can see a picture at following link.


Certainly not getting 12v out from module to blower but am getting 14v from plug to module. What are odds that new module is bad as well?

From what we tested so far i am leaning towards the control head as the problem. Besides power and ground going in to the module, you have a third wire which is the control from the switch in front. It regulates the amount of voltage applied depending on what fan speed you select. Example. high fan gets full voltage, low speed gets lower voltage, etc.
Hi, just doing a follow up to our conversation. Let me know whats happening and if i can help you further with info, etc. Thanks Eric
Customer: replied 5 years ago.
Okay, I ordered a new front controller head and installed it and still have no blower. Fuses still good, and no change in volt readings already provided. What next?
Customer: replied 4 years ago.
Relist: Other.
Responses from expert are too infrequent. Been at this for two weeks and have purchased $100+ worth of replacement parts and still have original problem.

Lets run back through from the beginning and see what were missing. Here is a diag chart for your problem. Do you have a scan tool able to get into body functions?

1. Access the rear blower motor, behind the Right Rear (RR) wheel, inside of the vehicle.

2. Test for constant B+ to the blower motor on the Orange wire.

3. Test for a constant ground to the blower motor on the Black wire.

4. Test voltage on the Purple wire at the blower motor.

5. Should have 0.4 to 4.0 volts as the blower control is moved from low to high speed.

6. Check Heat Vent Air Conditioning (HVAC) auxiliary blower data with a scan tool.

7. The blower command should change from 0 to 98% as the blower speed control switch is moved from off to high.

8. Check for HVAC auxiliary blower related codes with a capable scan tool.

Customer: replied 4 years ago.
I don't have a scan tool to pull related codes. Only have good voltmeter. As indicated above... Blk/purple wires to module read 4v to 3.4v as rotate control off to high but no blower. red/blk wires from module to blower only read 1v or less.
Hello, I'm Cam.
I will see what I can do to help you. Give me a few minutes to read through everything and see what has been done and tested so I can advise you with out redoing anything.
So I have a question, when you powered the blower motor directly, did you supply a power and a ground or just a power?

What I am wondering is if the the ground for that is bad. A meter would show normal, but when you actually put the amps to it, the ground can fail. If so I would suggest running the motor black wire to a redundant ground to the body and see what that does next.
Customer: replied 4 years ago.
I bypassed the blower module by using alligator clips to direct power from red/black wires that normally plug into blower module (14v) and clipped to input connectors of motor. Also did same with purple/black wires (10v) that plug to blower module. Used same black wire (ground) on both tests to motor.
OK so the ground is good then. I need some time to find the chart for this. I will reply when I get it. Thanks for your patience.
Here is the diagnostic chart, can you follow it?
Customer: replied 4 years ago.
let me run through these and I will get back to you. Thanks.
THanks, XXXXX XXXXX does not lead to a repair, let me know the results of each step so I can follow with you.
Customer: replied 4 years ago.



I still think my problem has to do with the Purple wire (Ignition 3 Voltage Circuit) not registering enough voltage to power a simple test lamp (6v-12v).


I followed the test descriptions you sent. Here are my process responses.


Step 1. Reviewed auxiliary HVAC operation and moved to Step 2


Step 2. Performed auxiliary blower functions but does NOT operate at any speed setting of the front and rear blower motor switches.. Got to Step 3


Step 3. Disconnected Auxiliary blower motor, turn ignition ON with engine off, connected a test lamp (and Volt meter) between the auxiliary blower motor supply circuit (Red wire from blower motor resister module) and a good ground and Test Lamp did not illuminate (voltmeter read 00.4V)... go to step 6.


Step 6. Disconnected the auxiliary blower "motor resister" assembly connectors, probed Ignition 3 voltage circuit (Purple wire) with test lamp connected to a good ground. Test lamp DID NOT illuminate. However, It did illuminate when I probed the Battery Positive voltage circuit (Orange wire). Go to step 15.


Step 15. Repair the ignition 3 voltage circuit of the auxiliary blower motor resistor assembly. Need to refer to "Wiring Repairs" in wiring systems but the referenced Hyper Link does not work. Can you provide Wiring Repairs instructions? Thanks. Also will need Test Description Steps 21 and beyond. Thanks.



Quick question, if you jump power from that orange wire to the purple wire, does the system operate correctly? Reply you with your results and I'll get you the rest of the information.
Customer: replied 4 years ago.

Not certain what you mean (Jump power from orange wire to the purple wire)? I have used alligator clips from Orange wire direct to motor positive connector and good ground and the motor did operate.

Do you mean for me to use the orange wire in place of the purple wire directly into the Motor Resistor Module?

That is exactly it, what you did with the jumper wire.

THe wiring repair is a generic document that outlines basically how to use a crimp connector.
You will need to follow through the wiring from the fuse block to find the bad connection. Below is the diagram. The RBEC is the right bussed electrical center.
the fuse block is the left dash fuse block. This is where it becomes difficult to find. I would test at the right bussed electical center, which is same idea as the left dash fuse block, but has no fuses .If the wire has no power, then consider running a new wire across. Good work getting this far. I am sure you will get this fixed in no time now.

And step 21 is just to verify it works, and if not, go back to step 1.

Customer: replied 4 years ago.

Cam, you have more faith in my ability than I do. I have always steered clear of Electrical Repairs. I am more your Pull and Replace component type of DIY mechanic. BUT... I'll give it a try. Hopefully, the wire coming out of the RBEC is also purple, and with any luck, is getting good voltage from left dash fuse block. If I do this, should I also consider splicing in a FUSE along the path? and what size fuse should I use?

Thanks for your help Cam.

The only reason to spice in a fuse is if you add a different power source.

If you do decide to, a 10 amp is enough.

The wire is a brown wire all the way from the fuse block. Why it changes to purple I don't know. It is still the corner pin, b1?
Customer: replied 4 years ago.

Brown wire, corner pin, b1. That's very helpful.... Thanks!

Done for the night. 9:10pm local.

Yes, brown in B1 is the ignition 3 feed. Let me know how it goes tomorrow.

Thank you for allowing me to assist you. Please rate my answer 3-5 and feel free to ask any follow up questions regarding this issue you may have. :)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 29570
Experience: GM Grand Master Technician 2007. 14 years experience.
GM Tech (Cam) and 4 other Chevy Specialists are ready to help you
Let's try this, at the rear switch itself. You have a brown wire that likely has two wires into 1. Does that get 12 V with the key on?
Customer: replied 4 years ago.

Rear switch brown wire, at connector, does not have 2 wires to 1. Traced brown wire back to mid-harness and located a brown 2 to 1 at that location. Registered no Volts with key in on position.


I'm becoming convinced that it is the rear controller Part number 1572860. I have been able to make the rear blower motor operate by bypassing at mid-harness (alligator clips) from purple wire to light blue wire and also purple wire to red wire. Also able to get rear blower motor to operate from rear switch connector (again alligator clips) where corresponding purple wire, light blue, and red wires go in. I get nothing if I plug rear switch connector harness (21 pin) into rear controller.



I am 100% convinced it is not! The controller receives power on that brown wire from the rear blower resistor relay assembly. The power comes in on one brown then splits off inside to power that brown. The brown gets its original voltage through the IGN 3 fuse which gets it power through the ignition switch.
Customer: replied 4 years ago.

your images are not showing up on my end. can you send as PDF.


if you're convinced... I'll try to follow the brown wire back to the corner pin, b1 tomorrow but I am not certain what I'm looking for when I look at the RBEC. Perhaps that's the photo you are trying to send. Thanks for your help.


I have my Suburban interior all disassembled on the inside anyway...

I am sure, and here are links.
Customer: replied 4 years ago.

Thanks for the images... wish I was better at reading Auto Electrical Schematics. :-( I'll dwell on these tomorrow and see what I can accomplish. Thanks for saving the cost of yet another part from Rock Auto. They're making a killing off of me.


They are not bad. Power flows from the top of the one, starting at the fuse, then follow the line. Where there is a dot at the point where 2 cross, that is a splice.

Follow it through the 2 I just modified.

Customer: replied 4 years ago.
Will do tomorrow... thx
Customer: replied 4 years ago.
Cam, let me know if I need to add more money to my account. I located the brown wire at the RDEC, tested with ignition on and off and received no volts. To get power to it, I jumped power from brown wire (actually a dual wire coming off connector at RDEC) comes from left side fuse block. Spliced wires with in line 10amp fuse. This provided 12 volts through brown wire back to rear blower controls, but still no power to blower motor. PURPLE wire to blower module still no volt reading.

Recap, I had no power going to brown wire (ignition 3 voltage circuit), spliced it to power (12v) coming off connector at RDEC, and now I have ignition 3 voltage running to rear controllers but still no blower.
OK, I can see this reply and will be back at my PC in about 15 mins where I can give you my full attention. Is that Ok?
Customer: replied 4 years ago.
Ok, so now, does the orange wire get power at the rear blower resistor assembly?
Customer: replied 4 years ago.
Yes, and always has (12v), the purple wire next to it does not, and black wire is good ground.
Ok at the rear blower resistor assembly, manually ground the Red, white and sark blue, see if the power then flows to the blower.
Customer: replied 4 years ago.
?? Red, white, and dark blue? Three wires go into resistor module are orange, black, and purple. Are we talking about wires at the harness that lead to rear controls?
Can you just recap the parts replaced, name only will be fine.
Customer: replied 4 years ago.
Resistor module and front controller to rear blower
Not the rear module though, that is what this is looking like at the moment. IT sends the singal then on the purple wire