Need some help - 1997 Tahoe Heater / Blower Motor

[MarcelMarechal]

Hey guys, hope all is well. When I turn on the blower to defrost my windows it doesn't work. I checked the fuse and it was toast so I replaced it. Then it still didn't work. SO I switched the starter and blower relays and then it started to work again for a while. Now it did the same thing and stopped working but I find it will randomly turn on and off by itself when I am driving but never works when I want it to. What do I do here?

 

[waveryd]

Drop the glove compartment and check the resistor which looks like coiled wire between two posts and ensure that they are intact and current passes through them with good connection. Also check the speed switch carefully by changing speeds slowiy to ensure the switch has good contacts. I had a '96 Suburban with 600k miles and had issues with both over the years. Lastly, hot wire the blower motor and wiggle test everything. Moisture and corrosion can take its toll over the years. If you suspect the motor you can swap the blower motor from the rear hvac unit to front to verify.

 

[OR VietVet]

Welcome to the forum.

Yes, like @waveryd said, check resistor and switch and even the blower to see what it does with direct power. Remember that the blower, I think, is supposed to run at a very low speed at all times for air circulation but on this rig, maybe not. Whatever you do, and figure out, use all new fuses and relays.

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

You are already receiving sage advice from the knowledgeable folks on this Forum.

 

[Hoesgottaeat2]

The switch in the dash is often a culprit with symptoms you describe as well. Replacement is pretty straight forward. Be sure to rule that out as well, if you haven't already.

 

[Eman85]

My money is on a melted connector on the blower switch. You can check power and ground at the motor first as it's easy to get to and then check the relay behind the glove compartment.

 

[Mean_Green]

I have a similar issue and will be checking all of these things. Planning a trip to a salvage yard, so might be able to pick up a switch if necessary.

Does contact cleaner work on them or are the contacts sealed?

Blower's a bit noisy too. Sounds like a rattle of some kind. Might grab one of those if possible.

 

[east302]

On the three that I’ve had, it was the connector on the blower switch (at the panel) that melted and caused the switch to work intermittently. It’s worth a quick check. You can buy a pack of the connectors and change it out. GM part 12064998.

Wiring diagram for a 98…

For the noisy blower, if there is rust on it then you likely have a water leak in the windshield cowl. Stick a mirror up inside the blower intake duct and you’ll see a self-tapping screw popping through the cowl. Water can leak in there (a then onto the carpet) so pull the screws on the cowl plastic and seal the holes up before reattaching. The blower would probably best then be replaced, but that’ll take care of the water leak.

Clean out the housing to the left of the blower at the evaporator while you’re at it. It gets gunked up pretty easily and reduces the airflow. Self-rinsing foaming a/c coil cleaner works pretty well.

 

[j91z28d1]

On the three that I’ve had, it was the connector on the blower switch (at the panel) that melted and caused the switch to work intermittently. It’s worth a quick check. You can buy a pack of the connectors and change it out. GM part 12064998.

View attachment 395269

Wiring diagram for a 98…

View attachment 395268

For the noisy blower, if there is rust on it then you likely have a water leak in the windshield cowl. Stick a mirror up inside the blower intake duct and you’ll see a self-tapping screw popping through the cowl. Water can leak in there (a then onto the carpet) so pull the screws on the cowl plastic and seal the holes up before reattaching. The blower would probably best then be replaced, but that’ll take care of the water leak.

Clean out the housing to the left of the blower at the evaporator while you’re at it. It gets gunked up pretty easily and reduces the airflow. Self-rinsing foaming a/c coil cleaner works pretty well.

yep, mine melted years ago. the oem blower motor started to get hard to spin and draw more current is what I think was the cause after all way said and done.

I tried 2 auto parts store blowers, both were noisy. ended up ordering a oem one, it was quiet and the switch plug never melted again.

for me the one setting below max speed melted, it was also the most commonly used.

 

[Mean_Green]

OP never returned.

Finally got a chance to dig into a few things.

Blower does not run (that I can tell) in any position other than High. And even then it doesn't sound right. Almost like something is loose.

Pulled the blower motor today. It's a Napa replacement, who knows from when, but it's all clean and tight. It does not spin freely by hand, but it isn't bound up either. When I connect it straight to a battery, it blows up a tornado. Wires that connected to it are OK, but the plastic shields over the 1/2 tab connectors are melted, ground is worse than 12V.

Resistor looks good to the eye. No discoloration or deformation. Wires and connector look good too.

Climate control appears to have been replaced at some time. Connectors are all good though, no signs of overheating.

Before I order a climate control, is there anything else to check?

 

[east302]

There are a couple of things that I’d check first.

On all but high speeds, power goes through the resistor and then to the relay.

Disconnect the connector at the resistor and check for voltage at the yellow, tan and light blue terminals using the chassis as a ground. The metal dash support bar would suffice. You should get 12V on each wire at corresponding blower speeds. Yellow is low, tan is medium 1, light blue is medium 2.

If that doesn’t check out, I’d replace the blower switch at the panel since you said that it’s connector is not melted. Pull the fan knob off and the switch just snaps into the control panel. The panel itself is really independent of the blower other than the plastic connecting it.

If you do get voltage at the resistor connector for the first three speeds, then the blower switch is good. Put it back together and pull the connector on the high speed relay which is next to it. Check for voltage (it will vary) for each fan speed at the blue connector.

If it’s good, then the resistor is good. If it isn’t, replace the resistor.

If it’s good, reconnect the relay and pull the power wire (purple) from the motor. Check for voltage using all fan speeds.

If you only get the 12V and no lower voltage, then the relay is probably the issue. If you do get varied voltage, then I’d swap the blower out.

 

[Hoesgottaeat2]

OP never returned.

Finally got a chance to dig into a few things.

Blower does not run (that I can tell) in any position other than High. And even then it doesn't sound right. Almost like something is loose.

Pulled the blower motor today. It's a Napa replacement, who knows from when, but it's all clean and tight. It does not spin freely by hand, but it isn't bound up either. When I connect it straight to a battery, it blows up a tornado. Wires that connected to it are OK, but the plastic shields over the 1/2 tab connectors are melted, ground is worse than 12V.

Resistor looks good to the eye. No discoloration or deformation. Wires and connector look good too.

Climate control appears to have been replaced at some time. Connectors are all good though, no signs of overheating.

Before I order a climate control, is there anything else to check?

In my experience with a '98 Burb I had with same symptom wound up being the climate control switch that you're leaning towards.

Do any of you other fellas have any idea what the resistance of that blower resistor should be here to test before eliminating that as a suspect?

 

[Mean_Green]

I'll see if I can dig up a meter tomorrow.

 

[Mean_Green]

Based on the pictures, I'm guessing the main issue is the switch is shot. None of those tests panned out. I get no voltage at all on any of the resistor connector pins in any setting. At the purple wire at the blower, I only get 12V when the switch in on high, but I get random fluctuating results when rotating the switch. I can hear and feel the relay actuating.

Connector to the switch shows heat issues on the plastic between the pins, but the pins and wires appear OK.

The whole unit is in question though since the end tabs are dry rotted and cracked so it doesn't mount properly.

On the Bay place, if I search 'climate control', I see them for around $50, but if I search 'blower control', they're all listed at $200 or more even though they all show the same item in the pictures.

 

[Mean_Green]

But I'm not sure that's the entire problem. With the blower motor completely removed, I still hear noise and what sounds like rattling. Is there another fan back under there some where?

Whatever it is changes as I push the AC or other buttons, but it isn't consistent.

 

[east302]

The melted connector (see post #8) is very likely your issue with the blower speed since you have erratic voltage at the resistor.

The replacement panels usually fall into the $200 range and there are differences in quality control compared to the GM part. I had one from dorman a few years ago that started smoking within a few minutes of installation. The backlights shined around gaps at the knobs and it had, overall, a cheap feel to it. I sent it back.

I’ve used the Delco 15-72547 (GM part 09378805) without issue. It came in a GM box and is what they would sell you at the dealership.

​

 

[Mean_Green]

The melted connector (see post #8) is very likely your issue with the blower speed since you have erratic voltage at the resistor.

The shell is only melted a bit, the pins and wires are fine, not discolored at all. Probably only did that as a result of the switch contacts overheating as shown in the first picture.


This is what I'm looking at. I just can't pop out another $200+ right now.

Pardon Our Interruption...

And I'm not sure what to do about post 15.

 

[east302]

If I were going to drop $200, I’d get the GM/Delco and avoid the typical aftermarket parts quality control issues.

In the interim, just to get it working, I’d replace that connector and the blower switch. That’s what fixed it when I had the same issue on three 98 models - the melted connector allowed the pins to barely move just enough to allow poor contact.

I’m unsure about the noise that you mentioned. There are no other fans or moving equipment aside from the air doors and actuators. One is on the recirculation door at the blower inlet and the other at the heater core behind the ashtray.

The internal gears in the actuators eventually crack and can cause a ratcheting or crackling sound as the actuator attempts to position the damper. Eventually, the actuator fails and the damper no longer adjusts.

Watch the silver position indicator dial to see how smoothly it rotates as the hot/cold is adjusted or (if you can see it) when the recirc button is pressed. That recirc actuator is really tucked up in there.

The heater (blend door) actuator:

Here is the recirculation actuator - viewed as though you were looking through the firewall into the cab with the blower being to the left in the photo.

 

[Eman85]

Electricity must make a full trip back to the battery so always check the grounds. Need to check voltage but many times with no load voltage might check good then the load is too much for the bad connection and the motor won't run. I would check input and output at the switch itself before I ordered anything. Then check at the resistor.

 

[Mean_Green]

I can't tell where those actuators are from those pictures, or how to get to them. That first one almost looks like it would be behind the radio.

The sound is constant as long as the key is rotated 'On'. I could see it being a spline turning inside a gear and it changes slighly when pressing buttons on the climate control.

If the gears have failed and the doors can't operate, would the motor(s) just continue to run?

Is there any kind of limit switch that would stop the motors?