• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

AC / Heat Blower Mower Not Working

Big T

Big T

Well-Known Member
Messages
12,985
Reaction score
29,315
Location
Fullerton, CA
The dash AC / Heat blower mower stopped working on my '99 Suburban. Check all fuses inside the cab and in the engine compartment and they were good. Rear AC works fine. No sign that it was going out. Last work I did was resetting the turbo to downpipe band clamp, replacing air cleaner and fuel filter. Any possible wiring to disrupt in those areas? Or is this just the switches going out? If the latter, how do I test? Do I have to pull the stupid dash down to fix?

Man the AC was working great, very cold. Still is on the rear. At the lowest setting the blower did have a feint squeek in it, but it disappeared at higher settings.
 
First thing to check is the power feed wire behind the glove box. next thing is to pull the cover off the blower motor and see if the blower is getting power and has a ground.
 
THEFERMANATOR said:
First thing to check is the power feed wire behind the glove box. next thing is to pull the cover off the blower motor and see if the blower is getting power and has a ground.
Click to expand...

1) What color wire is the power feed behing the glove box?

2) Can the cover on the blower motor be removed without pulling the dash?
 
Power feed is just 2 wires: red and black. It will have a plug in the middle that likes to melt down. Will be between the blower and the HVAC box in the middle generally. May be wrapped in a black foam blanket.

If the motor locked up the fusible links in the blower resister pack also burn out.

Cover on blower motor can be pulled out, but, the ECM tray has to come out. Some people just hack it out and tape it back in without ECM removal. :rolleyes5:

Motor can be rotated and it will come out with fussing - a tight fit.

Mower :rof:
 
I'm not good at this, so I need you to be more descriptive.

WarWagon said:
Power feed is just 2 wires: red and black. It will have a plug in the middle that likes to melt down. Will be between the blower and the HVAC box in the middle generally. May be wrapped in a black foam blanket.

Here's a pic of the wiring behind the glove box with the ECM removed:

attachment.php


I do not see red and black wires going to the blower. There is a single red wired with a plug in the middle. Could not separate that plug, but it does not look melted. There is a foam covered black cable, but that goes through the firewall.



If the motor locked up the fusible links in the blower resister pack also burn out.

Where is this blower resistor pack? How do I know if the the motor locked up?

Cover on blower motor can be pulled out, but, the ECM tray has to come out. Some people just hack it out and tape it back in without ECM removal. :rolleyes5:

ECM tray = that which the ECM slides onto? How do you get that out? I'm looking at it and do not see a way to do it.

Motor can be rotated and it will come out with fussing - a tight fit.

Mower :rof:
Click to expand...
 
Large red wire in lower left of picture may go to a two wire connector? You are in the right area to find this connector.

post #10 has a pic.

http://www.thetruckstop.us/forum/showthread.php?24689-No-Blower-Motor-at-any-speed

Other issues:

http://www.thetruckstop.us/forum/sh...ickers-w-blower-off-amp-erratic-or-no-airflow

Where is this blower resistor pack? How do I know if the the motor locked up?

Resistor pack is on top of that black box in the upper left of the photo. May have moved for '99?

ECM tray = that which the ECM slides onto? How do you get that out? I'm looking at it and do not see a way to do it.
Yes ECM tray has several screws that go down. Real PIA to get out in the front of the tray as they are sunk down in holes.
 
WarWagon said:
Power feed is just 2 wires: red and black. It will have a plug in the middle that likes to melt down. Will be between the blower and the HVAC box in the middle generally. May be wrapped in a black foam blanket.

If the motor locked up the fusible links in the blower resister pack also burn out.

Cover on blower motor can be pulled out, but, the ECM tray has to come out. Some people just hack it out and tape it back in without ECM removal. :rolleyes5:

Motor can be rotated and it will come out with fussing - a tight fit.

Mower :rof:
Click to expand...

It's a single wire in the 99 as I know by 98 GM had done away with the 2 wire connector that always failed. The single red wire that plugs into a connector behind the glove box is the blower motor feed. Make sure you have power to this wire as it powers the blower. the plastic cover can be removed without pulling the dash as well as the blower, but like warwagon said you have to either pull the ECM tray or break the top portion of the plastic cover(mines been broke for quite some time now and hasn't fallen off). there will be a purple wire that powers the blower, and a black ground wire that hooks to a grounding tab on the blower body. The 2 wires can be removed without poulling the cover as they have to come off to remove the plastic shroud cover.
 
THEFERMANATOR said:
It's a single wire in the 99 as I know by 98 GM had done away with the 2 wire connector that always failed. The single red wire that plugs into a connector behind the glove box is the blower motor feed. Make sure you have power to this wire as it powers the blower. the plastic cover can be removed without pulling the dash as well as the blower, but like warwagon said you have to either pull the ECM tray or break the top portion of the plastic cover(mines been broke for quite some time now and hasn't fallen off). there will be a purple wire that powers the blower, and a black ground wire that hooks to a grounding tab on the blower body. The 2 wires can be removed without poulling the cover as they have to come off to remove the plastic shroud cover.
Click to expand...

I separated and tested the plug on the single red wire and one side has 12 volts.

I can see two small hex head screws on top that hold the ECM tray in place. Well there's a third on a lower support but the tray is not slid under that from previous work. After removing the tray, what else needs to be removed to get the blower motor out?

I see the purple wire, but can't get it off. I think I see the black wire connected to the blower off to the right. Do I need to remove these to get the blower motor out?

I really don't want to break anything. That's sorta cave man style.
 
OK, here's my progress:

1) Pulled the ECM tray via screws. Very simple.

2) Pulled the purple and black wires from the blower motor and pulled the soft plastic cover off the blower motor. It's a wriggle, shimmy and a blower dance to get out, but not that hard.

3) Using a spare battery, hooked + / - leads to purple and black posts on the blower motor and it RUNS full speed.

4) Test purple and black leads and no power.

So, it's not the blower motor. Where's my problem at? Resistor pack?
 
Did the blower run at all with it hooked up to the factory wiring? If it didn't run at all then you may have a bad blower motor switch in the A/C control. It is replaceable separately from the whole assembly. If it runs on high but no other speeds then your resistor is bad. If it runs on all speeds but high then your blower relay is probably bad. Of course you could have both a bad relay and resistor. your going to need to get a test light and start checking things to narrow it down.
 
THEFERMANATOR said:
Did the blower run at all with it hooked up to the factory wiring? If it didn't run at all then you may have a bad blower motor switch in the A/C control. It is replaceable separately from the whole assembly. If it runs on high but no other speeds then your resistor is bad. If it runs on all speeds but high then your blower relay is probably bad. Of course you could have both a bad relay and resistor. your going to need to get a test light and start checking things to narrow it down.
Click to expand...

Blower did not run at all when hooked up to factory wiring.

Where is the A/C control? Resistor? Relay?

I looked on RockAuto at the Resiistors and the AC Delco version is vastly different from the rest which have big spring coils on them. The PO who sold me the truck had a box of new parts and one of them looked like the big spring off brand version of the resistor.
 
Is this the A/C control:

attachment.php


I was able to pry off the bezel frame on the dash and then pop it out. How do I test it?

I had one of these on the '95 wreck, but Paveltolz took that.
 
Post #6 has a link describing the A/C control issues.
 
WarWagon, I looked at both links in post 6. One talks about getting settings 1 thru 3 on the blower, but not the 4th or Hi setting. I currently get nothing from the blower, though a direct test on the blower motor using leads connected to a separate battery got full speed out of the blower.

Both the AC and Recirc lights still work, so the first link in post 6 is definitely N/A. The second link was confusing to say the least.
 
Test the resister pack for getting 12v. Try any speed but high. If you get 12v to the resister pack it is burned up. Replace it and the blower motor. If the blower stops while the motor is getting power the resister coils heat up and burn the heat fuses out.

Likely as high doesn't work: If you don't get 12v to the resister pack replace the blower switch on the control head as it is cheap. If that doesn't fix it replace the control head. The repair in the 2nd link is complicated.

You could check the plug for 12v at the blower switch.

Assume you have checked all fuses?

Again making sure the red wire has power and a good ground is critical. This issue appears to be corrected for 1999.

Try a direct ground to the blower motor and see if it comes to life with the normal positive feeding it.
 
Joshua "WarWagon" thank you for calling me and working through this. I jump tested across all the nodes at the plug to the AC Control switch AND I get all 4 speeds out of the blower. The first time I did not listen closely to low, it was that quiet. I think this nails it down to the AC Control Switch and I'll order one from RockAuto.

Thank you, Thank You, THANK YOU!
 
THEFERMANATOR said:
You can buy the blower switch separate from the control head for about $20 VS the $150 or so a new control head costs. I'll try and see if I can find the part number for you. http://www.flashoffroad.com/Maintenance/hvac/imageHVACprob/gmc_ctrlhead.pdf
Click to expand...

http://www.rockauto.com/getimage/ge...m/smartpages/partinfo_resize/DUS/15-72275.jpg

AC Delco Part #1572275.

Wait the description on that says "Switch, Heater Control Blower. It also shows only 4 prongs, whereas mine has 8.

Is it alright to just replace this, or do the other parts on this control panel eventually go out?
 
The blower motor switch should be all you need.
 
You must log in or register to reply here.
Back
Top