2011 Jeep Liberty - Weak airflow from vents after about 20 mins of driving

Hello all!

Last week I finally got around to getting the HVAC distribution box replaced on my Jeep. Before that fix, air was not coming out of any of the dash vents. Everything works fine now in that regard. Air blows out from any vent now… but there’s a new issue. When first turned on, the amount of air blowing from the vents is plenty strong, but after about 20 minutes or so of driving, the air gets very weak. Hardly blowing anything out even on high. First thing I did was change the cabin air filters. Didn’t help.
I brought the car back to the dealership and they could not find any issue. Said they let it run for an hour and air pressure stayed the same. Said they check the fan for debris but it looked fine. But the issue persists.
Perhaps it only when the car is being driven, since they couldn’t replicate the problem?
I was thinking maybe the blower motor is simply on its way out. It does run quite loud on high. Or could something else be the culprit?
I would appreciate any help you all could give me. Thank you!

That just happened to me with the a/c on, the evaporator was freezing up because the freon was low. Have an independent shop that’s good with a/c check that out. Mine added some, now it works great in 108F weather.


The AC is blowing out cold. It’s not the temperature that’s the problem, but the amount of air.

The ice that’s forming keeps it cold, but blocks the flow. See if the the flow returns when you turn off the a/c but keep the fan blowing. If so, it’s the evaporator freezing up. If not, then it’s some other problem.


I will check that. Thanks!

I second what @texases said. Listen to his good suggestion.

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I hear air from vents. I don’t hear OP saying cold air.

A couple posts up.

OP says cold air.

Might make an appointment with an independent Air Conditioner shop . Drive around for 20 or 30 minutes before you get there and that may help find the problem .

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If the evaporator temperature sensor is not properly installed, the compressor won’t cycle and you will experience icing while driving, but not while idling.

If the refrigerant level is low, the air would blow 65 to 70 degrees at idle.

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An airflow block at any point in the loop could cause this. The air flow loop begins at the exterior vents at the bottom of the windshield, from there inside and through the evap core, blower cage, cabin filters, blend doors, and dash vents. If the A/C is in Fresh Air mode then the cabin air has to get back outside somehow, soften via hidden vents, usually at the rear of the vehicle.

So first step, clean debris from the air intake venting at the bottom of the windshield. Next step, do the symptoms change according to Fresh Air mode or Recirculated Air mode setting?

I’m guessing either the frozen evap core problem cited above, or some sort of hvac door problem.

I would suggest having the refrigerant charge checked on the A/C system. If the charge is a bit low that can cause evaporator freezing. The low side pressure is roughly equivalent to the temperature inside the evaporator. E.G., if the low side pressure is say 30 degrees or less the temperature will be too and since that is below freezing the evaporator may ice up. Adding some refrigerant will likely fix this as it will bump that low side pressure up to slightly above freezing.

To test; when it is acting up shut the car off for a bit. Wait about 10 minutes and look underneath the car on the passenger side. You will likely see a very heavy condensation drip due to the melting ice. Hope that helps.

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Thank you for all the helpful replies! I will most likely bring the car in to a shop soon. I’ll let you know the outcome.