NEED HELP Fan control module failed again

[Riktar]

After some research I thought I replaced the failed fan control module on my 07 TB which corrected my fan always on condition. Unfortunately the fix only lasted a few weeks with the same symptoms (Fan continues to run even after the TB is turned off. Temp solution is to pull fuse #35 in the under the hood fuse box) occurring.

I suppose it could have been a bum replacement part but I would like to seek the counsel of this forum to see if there is any other reason for the control module to fail.

 

[Blckshdw]

This is a new one, I haven't heard of before. To satisfy my own curiosity, are you able to change the blower speeds, and which vents the air blows out of on your control unit, even after the ignition is off? Or does the fan always blow at the last speed setting that was set?

 

[Riktar]

No on changing the blower speeds or changing the venting from the controls. And in terms of the fan staying on after the key: It's always locked on the highest fan setting. With the TB running I have tried changing the fan speeds and no joy. The fan just runs wide open.

 

[budwich]

It would appear that the relay in the module has stuck closed which causes your problem. Not sure how serviceable the actual module is but you might try "autopsy" it to see if indeed the relay failed / stuck / broke or something is holding it up (eg. stress on the board / component).

Of course, other electrical test to see if the selector is actually operating electrically correctly should be done as opposed to doing the "moved the switch and nothing happened" testing which does not tell you much about the condition of the electrical paths.

 

[TollKeeper]

Is it possible that his fan is starting to fail, and causing a high voltage spike when turning on, spark welding the relay?

 

[budwich]

anything is possible... without some investigative work, the wallet and replacement effort are the "tools of the day".

 

[Riktar]

Thank everyone for the suggestions! I will do some digging to see what measurement I can take for the fan to see how much it is drawing when hooking 12 volts to it.

 

[budwich]

not sure that the current draw will tell you much as I am not sure people know the power rating for the motor. IF you have to old one, I would pull the cover on the relay to see what's up. Go from there.

 

[Riktar]

While that is a great idea I took advantage of Amazon's return policy and sent the first replacement module back already.

Who knows? Maybe it was a case of just getting a bum replacement. My luck never seems to work out like that but hey, there is a first time for everything..... 😉

 

[budwich]

no problem... "free replacement" works for me. I guess then you are looking at crossing your fingers and hoping that the next will last a "bit longer". Outside of that (once the free replacement program ends), then you can start looking elsewhere... lots of posts about fan motor excessive draws, connectors melted, poor / oxidized connections, poor switches, on and on.

I normally work from cheapest / free to expensive and more work... but it depends on the problem.
Odds are high that the motor might be on its way out but it could be other things... but again without doing some checks (resistance / continuity / etc), it could be lots of areas.... or just bad luck.

you didn't actually mention the manufacturer of the modules that you have tried so far.

 

[Riktar]

This is the link to the part I ordered from Amazon:

Amazon.com: ACDelco 15-81773 GM Original Equipment Heating and Air Conditioning Blower Control Module: Automotive

Buy ACDelco 15-81773 GM Original Equipment Heating and Air Conditioning Blower Control Module: Blower Motors - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

 

[TollKeeper]

Personally... Not a part I would have bought...

 

[budwich]

This is the link to the part I ordered from Amazon:

Amazon.com: ACDelco 15-81773 GM Original Equipment Heating and Air Conditioning Blower Control Module: Automotive

Buy ACDelco 15-81773 GM Original Equipment Heating and Air Conditioning Blower Control Module: Blower Motors - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

ok... so now you need to clear up another question.... what type of controls do you have? manual or automatic?

 

[mrrsm]

This was First Hinted at by @Blkshdw in Post #2:

Check out this video for "The Toss Up" Choice between either The Blower Motor Control Module or in this case... the much more likely suspect...The Automatic Climate Control Module improperly sending PWM (Pulse Width Modulation) Grounding Signals along the Purple Wire to keep the Blower Motor Running ...even when the HVAC Switch/Key are turned OFF.

Perform a Quick Check of the Harness Wiring Connector with a DMM set to VDC checking the harness lead coming from the ACCM after unplugging it from the BMCM and then inserting The RED Test Lead between the 12 Volts DC (Red) Hot Lead side of the Connector while inserting the Black Test Lead at the Purple PWM Ground Connector.

This action should reveal if any Voltage is present and the ACCM is still LIVE with the Key Off ...and sending Grounding Signals along the Purple Wire at the WRONG TIME ...versus the problem being within the recently replaced Blower Motor Control Module:

 

[Riktar]

I have the automatic.

Thanks for the video and the suggestion for checking voltage! I am off with the multimeter this weekend to see what I find!

 

[budwich]

I have the automatic.

Thanks for the video and the suggestion for checking voltage! I am off with the multimeter this weekend to see what I find!

ok... well that helps me. forget about the "relay part", there is no relay in the automatic climate control system... its a power FET design which is "modulated" to provide the appropriate "chopped voltage cycle" to provide the "right amount of powering" for a given speed. As such, it is possibly that the main controller is not operating correctly as suggested in the post by mrrsm. Having said that, the "power switch fet" is the weak point and if the draw is too great, it will be "harmed".