1988 Grand Marquis - new blower motor, almost no air coming from vents?

[Tynnerstroem]

Hello friends,

I have a 1988 Grand Marquis with manual A/C (no Auto-option on the HVAC panel) that I changed the blower motor in, to a new one from RockAuto. A PITA to get to those bottom bolts for sure but I managed to do it. The issue now is that there's hardly any air coming out of the vents.

I have done no other work to the HVAC system itself. I can tell that the fan speeds change properly when I cycle through them, because the fan audibly changes through low to high, and the airflow goes from non (on low) to very little (on high). I also note that what little air does come out of the vents will change zones (panel, defrost, floor) as it should when I change it on the panel.

So to my amateur, driveway technician mind there is something blocking the air from the blower motor making its way to the vents, but what could that be? Getting the new blower motor in place was a bit of a pain, could I have hit something on the inside of where the motor goes to block the passage of the air? Or could it be something else acting up?

Thank you kindly in advance!

[kishy]

Any possibility of a mouse (or whatever locally prevalent small rodents are near you) nest inside the vent ducts? You'd surely smell it and presumably know about it, but it's definitely one way for stuff to get piled up inside the ducts, blocking them.

The flaps/doors which control the air flow to the various vent options (e.g. windshield defog vs panel vents) have hinges which consist of thin plastic which flexes back and forth. This, naturally, has a limited lifespan and eventually breaks. I wonder if one of the flaps has broken off and is unable to move to the correct position, and is now blocking airflow.

Some relevant photos here: https://www.grandmarq.net/vb/forum/t...29#post1160529

[Tynnerstroem]

Thanks kishy! There's no smell indicating anything in there, and up until I changed the blower motor air was properly coming out of all the air vents on the dash. Of course things will break when they break, but it's just such an irritating coincidence.

A flap could definitely have decided to break after 36 years. To get into the plumbing seen in the pictures, I assume the dash is coming out? If so, how much of an investment in time is that? Could the dash be out and in the same day? Is it a weekend-long job?

[kishy]

Oh, another possibility then, since it worked before: did the blower motor come with the blower wheel attached? If so, remove it and compare to your original. Maybe the fins are angled for rotation in the opposite direction. In that case, transfer the blower wheel off the old motor to the new one.

Or perhaps the new motor spins in the wrong direction. I'm not sure if that could be as simple as reversing its polarity (swap the two wires). Some of the aftermarket motors come with just bare wire ends and you splice them onto your original connector - was that the case for you?

Yes, to access the area shown in the photos, the dash must be removed. It's a significant undertaking. Let's verify the motor is spinning the right way first.

[Tynnerstroem]

Oh, another possibility then, since it worked before: did the blower motor come with the blower wheel attached? If so, remove it and compare to your original. Maybe the fins are angled for rotation in the opposite direction. In that case, transfer the blower wheel off the old motor to the new one.

Or perhaps the new motor spins in the wrong direction. I'm not sure if that could be as simple as reversing its polarity (swap the two wires). Some of the aftermarket motors come with just bare wire ends and you splice them onto your original connector - was that the case for you?

Yes, to access the area shown in the photos, the dash must be removed. It's a significant undertaking. Let's verify the motor is spinning the right way first.

It did come with the blower wheel and everything. Rookie mistake perhaps, but the old motor has been tossed. It never did occur to me to compare the angles, but I had to splice it on like you mention so I will at least try to reverse the wires and see where that gets me.

[sly]

I just changed the blower in my car as well... I tested after install without starting the car and it barely blew any air, but after starting the car, it ran great. Seems it really needs that extra 2-3 volts.

[gadget73]

I could swear someone else recently did this and found that the new motor runs the wrong way, and the fix was to re-pin the connector to reverse it.

[Tynnerstroem]

Thanks to the both of you sly and gadget73! I have tried it with the car running and the issue persists. It does give me hope that it seems re-pinning the wires could solve it.

[Tynnerstroem]

For the record, it was indeed the motor running the wrong way. I reversed the wires and it works great now. Thank you all very much for your help!

[sly]

Strong airflow makes for good AC.