2012 Freightliner M2 blower motor doesn't work on HIGH SPEED

[Monkeywithawrench]

So my service truck 2012 Freightliner M2 blower doesn't work on HIGH speed. Every other speed works (1-4), just not high. I replaced the blower motor last year. Tried a new control head........no joy. Its driving me nuts why this isn't working on high. So the blower motor has the 3 wires...Big black, Big Blue, and little blue. All speeds the big blue and black (Power and Ground) provide 12V so its not the usual suspects of a power issue at a connector or fuse block. The little blue wire (which is the speed controller for the stupid board inside the fan is doing what it should. With the plug connected to the fan, fan running on the different speeds, the reference voltage from the small blue wire coming out of the plug at the fan steps down in voltage with higher speeds.

SPEED BIG BLUE WIRE VOLTAGE (FAN POWER) LITTLE BLUE WIRE VOLTAGE (SPEED CONTROL)
0 (0FF) 12V 11.62V
Between 0 and 1 12V 7.51V
1 12V 6.49V
Between 1 and 2 12V 5.49V
2 12V 4.46V
Between 2 and 3 12V 3.35V
3 12V 2.34V
Between 3 and 4 12V 1.34V
4 12V 0.63V

So it seems every speed higher is a drop of about 1V on the signal wire at the blower motor. I've tried grounding out the signal wire to the ground wire at the plug on the fan..........one would assume that the fan would kick into HIGH with no reference voltage for the speed signal, since with the fan switch in the OFF position it gets 12V on the signal wire.
I'm assuming the blower motor control board 'MIGHT' be bad since its not kicking into full bore HURRICANE mode. I'm just not willing to throw another $250 at a blower motor just to try it.

Anyone run into this problem?? Anyone have this type of blower on their truck?? I'm wondering/ would like to know what they get for voltage at the signal wire on HIGH SPEED (4) , plug inserted into working blower motor.
Thank you!!

 

[Monkeywithawrench]

Pics of voltage readings and speed control

 

[Monkeywithawrench]

More pics, voltage readings and speed control

 

[Monkeywithawrench]

Speeds 2.5 and 3 voltage readings

 

[Monkeywithawrench]

Speeds 3.5 and 4 (HIGH SPEED) with voltages......sorry about the glare from the meter.
Sooooo, by following the path of logic; this blower motor 'SHOULD' work on high?? Same results with a new control head. I'm leaning towards the NEW BLOWER motor that I put in last year is defective. WHY CAN'T WE JUST HAVE A NICE SIMPLE RESISTOR SETUP LIKE WE'VE HAD FOR YEARS!!

 

[398370]

Before bought new blower motor remove old one and throw on bumper jumper with battery and see if hits hurricane force just my 2 cents

 

[Monkeywithawrench]

LOL!! Not with a whoosh of fire, but a whisper of smoke!! Took blower out yesterday and did that. Put alligator clips on pins for 12+ and 12- (Big blue wire and Big Black wire), put probes into plug for 12+ and 12-. Turned it on. Even though the alligator clips had insulating boots on them the 12+ alligator clip touched the signal (little blue wire) pin. Small wisp of smoke from probes, fuse popped, and now we have nadda!! No life in the stupid blower motor. Replaced fuse (30A mini), have 12V at plug, no response from blower motor. Ordered a new one off Amazon. Guess I should have left well enough alone. Ohh well, will report results when new one shows up.