Blower motor failure, removal, post mortem

[2seater]

 

I can understand that. I'm in the same boat.

 

Me too, but it's all good. Can't understand where the time came from to work??

[Ronnie]

 

Me too, but it's all good. Can't understand where the time came from to work??

 

Yeah, money is tight but it's nice to get up in the morning and say, "What do I want to do today?".

[heygibb]

 

 

The tests don't actually tell you the blower module is bad because other factors could be causing the fan to not get proper power to make it operate. For instance you could have 12 volts at the fan connector as you do but the fan would not run if there wasn't enough amperage to power the blower motor due to a loose or dirty connection, bad fuse, etc. somewhere in the circuit. However, if that was the case you would see the voltage drop as soon as you apply a load to the circuit. Perhaps back-probing the fan motor connector for 12 volts with the blower motor connected might give you an indication of what is going on.

 

I just did a load test, of sorts.

Voltage at connector that plugs into blower motor, unplugged and hanging free, w/ no key involvement, is 12v

Voltage via pins I inserted through insulation on plug wiring is 12v

Voltage at pins after I plug in suspect fan is .03v

 

Interpret this for me. I've rechecked fuses associated w/ HVAC...all OK.

[2seater]

Sure sounds like phantom power through the module, but I am not electrically savvy enough to know for sure. Do you have a 12 volt item of some sort you can jumper from the blower plug? Even something like a taillight bulb or something like that to bleed off floating voltage if it exists. If I get the chance, I will see about checking voltage at my blower plug under the same conditions.

[Ronnie]

I just did a load test, of sorts.

Voltage at connector that plugs into blower motor, unplugged and hanging free, w/ no key involvement, is 12v

Voltage via pins I inserted through insulation on plug wiring is 12v

Voltage at pins after I plug in suspect fan is .03v

 

Interpret this for me. I've rechecked fuses associated w/ HVAC...all OK.

 

This is just a guess from past experience.... As strange as it seems that might be normal operation of the blower control module with the key off. If your last test showed 12 volts instead of .03 volts I would say the blower module is bad. I'm not an electronic expert by any means but my reasoning is that the module varies the voltage most likely with SCRs or similar electronic components. Unlike a set of electrical contacts that open the circuit completely, the electronic components may have voltage passing through them at all times but not enough amperage to run a motor.

 

You should perform the same 3 tests with the key on and the fan control set to high to see what results you get.

[heygibb]

Sure sounds like phantom power through the module, but I am not electrically savvy enough to know for sure. Do you have a 12 volt item of some sort you can jumper from the blower plug? Even something like a taillight bulb or something like that to bleed off floating voltage if it exists. If I get the chance, I will see about checking voltage at my blower plug under the same conditions.

 

Absolutely great idea. I'll find something that draws 12v and test wiring under load.

That would be great if you'd pull your blower motor plug and check voltage w/ key on and off. I am going to guess you don't have 12v either way, if your AC is OFF. I think module acts as a rheostat and controls speed of fan w/ different voltages as you increase fan speed in car. If it is blown/fried, it releases full 12v down the line by default.

[heygibb]

 

 

 

You should perform the same 3 tests with the key on and the fan control set to high to see what results you get.

 

I'll do that.

[2seater]

My car has been idle for approx. 24 hrs, and with it in that condition, I get 2.2mv at the blower plug, disconnected. The meter will float around at more than that disconnected, so essentially nothing is coming from the module when shut down.

[heygibb]

My car has been idle for approx. 24 hrs, and with it in that condition, I get 2.2mv at the blower plug, disconnected. The meter will float around at more than that disconnected, so essentially nothing is coming from the module when shut down.

 

That tends to point in the direction we are all thinking...bad module on my end. Here are the results of some more testing.

 

 

Motor unplugged, key off   12.3v @harness plug       key on, 12.3v    engine on, 14.3v

 

Motor plugged in, key off   .3v @harness plug     key on, .3v     engine on, AC OFF  .31v

                                                                                                 engine on, AC ON   .33v

 

12v cargo lamp plugged in to harness    key off, .05v     key on, .05v     engine on, AC OFF  .05v

                                                                                                               engine on, AC ON   .06v

12v cargo lamp works when wired directly to car battery 

 

Apparently, the control module isn't producing the amperage needed to power anything requiring 12v. Under load, the voltage bottoms out and I don't quite comprehend what is happening, electronically.

Do any of you think there is any kind of risk for me to plug my new motor into this module? Or should I just go ahead and replace it prior to plugging in the new motor? I'm leaning toward the latter, but would like your analysis and why.

[Ronnie]

 

 

12v cargo lamp plugged in to harness    key off, .05v     key on, .05v     engine on, AC OFF  .05v

                                                                                                               engine on, AC ON   .06v

 

While performing the above test I would back-probe the orange wire (12 volts - hot all the time) going into the blower module and see if you see a drop in voltage. If that voltage stays at ~12 volts the problem is likely a bad module.

[heygibb]

I'll do that tomorrow. Let me know if there is anything else. Thanks.

 

I found the schematic we need to troubleshoot components. The fusible links caught my attention when looking at the layout, but the troubleshooting chart doesn't mention them (unless I overlooked it). I'll follow the procedure tomorrow and see what I find out.

 

[heygibb]

On 8/18/2017 at 10:14 PM, Ronnie said:

 

While performing the above test I would back-probe the orange wire (12 volts - hot all the time) going into the blower module and see if you see a drop in voltage. If that voltage stays at ~12 volts the problem is likely a bad module.

 

I tapped orange line, which splits into two purple lines at a fusible link. One goes to module and one goes to fan.

With the 12v cargo light plugged into blower motor connector, the voltage drops to .05v w/ key off and key on.

W/ engine running, AC OFF, voltage bumps up to .06v

W/ engine running, AC ON, it's .07v

 

If I perform the troubleshooting chart above, can I access the BCM and programmer wires from the engine bay side of the firewall, or do I have to access them by pulling the glove box? The attached pic is the engine bay side of firewall on the passenger side. I'm not sure what I am looking at.

 

[Ronnie]

I don't believe we are on the same page with the last test but your charts may be the right way to troubleshoot the problem.

 

What I had in mind is checking to make sure there is 12 volts available to the module before moving on. I just checked my module at connector C1 (photo 1 - see FSM 8A-66-1 for more info) that has the orange wire connected to it. I used a pin slid in beside the orange wire (photo 2) to make contact with the circuit that actually supplies the power to the blower motor via the blower module.

 

With the key off I got 12.5 volts on the orange wire. With the key on (engine not running) and the blower fan on high I got 11.8 volts which is about what I expected. There is a slight drop in the voltage due to the blower running and other items in the car being powered with the key turned to "run" and the engine not running.

 

It would be a good idea to test your car the same way to make sure your module is getting full power on the orange wire before proceeding to testing using the chart.

[heygibb]

On 8/19/2017 at 8:56 PM, Ronnie said:

I don't believe we are on the same page with the last test but your charts may be the right way to troubleshoot the problem.

 

What I had in mind is checking to make sure there is 12 volts available to the module before moving on. I just checked my module at connector C1 (photo 1 - see FSM 8A-66-1 for more info) that has the orange wire connected to it. I used a pin slid in beside the orange wire (photo 2) to make contact with the circuit that actually supplies the power to the blower motor via the blower module.

 

With the key off I got 12.5 volts on the orange wire. With the key on (engine not running) and the blower fan on high I got 11.8 volts which is about what I expected. There is a slight drop in the voltage due to the blower running and other items in the car being powered with the key turned to "run" and the engine not running.

 

It would be a good idea to test your car the same way to make sure your module is getting full power on the orange wire before proceeding to testing using the chart.

 

We're back on the same page. I'm tapped in at the module, as you have done now.

I'm getting 12.4v w/ no key on, and cargo light plugged into blower motor harness.

When I turn the key, no engine start, it drops to 11.8 because of my ABS brake pump.

I get 14.5v when engine started. Voltage not affected by any climate control selections i.e. AC or front Defog w/ high fan setting

Flash reflection in pic washed out VOM readout.

 

[Ronnie]

This thread is getting long and I can't remember it all too well. When you did the  HVAC Programmer Test  did you get the same results I did? If so your problem almost has to be the blower control module. Maybe the fan motor being hard to turn caused the module to go bad???  I notice the color of the wire you tested on your '90 was red/black and mine was orange but I think were were testing the same circuit. You did have the fan motor plugged in when you did the test didn't you?

[heygibb]

On 8/20/2017 at 2:38 PM, Ronnie said:

This thread is getting long and I can't remember it all too well. When you did the  HVAC Programmer Test  did you get the same results I did? If so your problem almost has to be the blower control module. Maybe the fan motor being hard to turn caused the module to go bad???  I notice the color of the wire you tested on your '90 was red/black and mine was orange but I think were were testing the same circuit. You did have the fan motor plugged in when you did the test didn't you?

 

My results were w/ fan plugged in.

I overlooked you have an '88. I have a '90. Maybe that explains the wire color differences. The orange wire I probed first attempt is shown at the lower left in my pic.

Here are my results on my “NO BLOWER OPERATION” test I posted about above.  I removed the glove box to access the BCM/ECM/Programmer area. I still don’t know for sure if my power module is bad or not. From the testing, my blower motor could still be the sole problem. I’ll know more once I install my new motor in a day or two.

[retired mechanic74]

....I have read some of the posting here and thought I would tell you what I did. The fan motor would not shut off with the key and after checking I condemned the blower module and called the part store and was shocked to find that it cost $177.00 SOOoooo I took a blower resistor from an older model Chrysler that uses springs for resistance and rewired the system and installed a three way switch under the steering column. Everything on the touch screen still works the same but I control, off hi and low, by the switch.

[heygibb]

That's an impressive fix, rm74. Thinking outside the box is necessary sometimes.

I'm still running through options. My new fan motor would not turn so I pulled a power module from a salvage yard yesterday. My fan will now run, but won't shut off. Sounds like I have a partially viable module, so to speak. I'll probably make another trip to the u pull it and scavenge for another.

[heygibb]

I've been busy w/ other obligations and was frustrated the module I pulled wasn't operating properly but am back for a status report. When I attached the u pull it module to my system at the salvage yard, the blower fan operated at all speed settings. However, when I shut it down w/ climate control settings, the fan still turned. I was happy I had moving air again but disappointed the fan would not shut off...particularly since I had spent 3-4 hrs in 100 degree heat scavenging for the one module I could find. (My body can't handle that kind of stress anymore (I'm 64) so it wore me out, tbh. What can I say. Getting old has its drawbacks.) But, wonders never cease.

Once I got home, I reconnected the module and fan motor, uninstalled, and it responded perfectly. All speed settings worked and fan shut down when turned off. Not sure if the extreme heat had something to do w/ the anomaly at the yard but I felt good about re-installing everything in its proper place.

I used some info from DAVES89 and others, to clean out my evaporator as best I could, while I had the plenum accessible. I used a small night light on a cord to lay in there to see better. I made a homemade scraper, of sorts, out of baling wire that would enable me to scrape any pine straw/leaves out that were wedged between the evap and the firewall.

 

 

[Ronnie]

Thanks for letting us know what it took to fix it!