I have a similar problem as the one posted about rodents/acorns in the blower wheel only this is a 2002 Ram pick up. I also found a nest under the rear seat. No real damage though. The one solution that was provided does not help me. I'm aware that mice and chipmunks can get thru tight spaces but the cabin-air intake still shouldn't allow rodents to get in. Are they really getting past the cowel? That seems pretty tight. Any other thoughts out there? Thanks

Replace your cabin air filter

the best first thing to do is check for a rodent nest in your system, look into the hvac air intake which should be under the cowl cover on the passenger side. if there is debris in there you have a rodent nest which needs cleared out. if your vehicle has a cabin air filter this is where the intake for the hvac is.

Could have a vacuum leak , Is the check ENG. light on ? Could need spark plugs, plug wires ,distributor cap . The IAC motors ,idle air control motor passage could be plugged with carbon. Bad mass air flow sensor could do it. Check for critter nests , found that cars that sit for a while , squires and rodents like to make nests under the hood . I have found air boxes full of dog & cat food. They take insulation and make nests. Check the Air Cleaner Restriction Indicator
The air cleaner restriction indicator is located on the intake duct between the air cleaner assembly and the mass air flow (MAF) sensor.
If the area inside of the clear section is green, no air filter service is required. If the area inside the clear section is orange and Change Air Filter appears, replace the air filter.

Just read an article in Brake & Front End, (a professional
trade publication ) in the last hour ,about mice eating
the cop ignition wires on 1 coil & going under intake &
eating the knock sensor wires ,on a 2002 Lexus

They didn't say how to stop that

Usually they get into the ducting & you get no air to the
motor, after they bring in their nesting materials & food

take out blower motor and use a vacum you might have too use smaller hose on it

I know this may sound nuts but you should check these things first, pull fan motor and look in the squirrel cage, i have cleaned out several gm and dodge blowers full of nesting material like insulation and acorns.....yes acorns...rodents love to fill the fans up as nests...yes they can get in where you cannot tell. next look at the connectors at the blower motor and where the wiring connects to the resistor pack, usually located on the ac case under the hood or near the blower housing. check the connections to se if they are burnt or melted. the resistor pack could be bad also. hope this helps....

GO TO HOME DEPOT OR LOWES THEY CAN TELL YOU WHAT TO PUT DOWN AND AROUND VAN TO KEEP RODENTS OUT.YOU NEED A FEW CATS AROUND THAT CAN HELP SOME.

I have seen that most of the time rodents will build a nest right in the middle of the fan on the blower motor. Remove the blower motor and clean the blower fan and clean out the air duct from the blower motor while it is out of the vehicle.

The blower motor is either bad or there is a rodent nest in the basket. Remove the blower from the heater box and inspect. If there is not a nest in basket then the blower will need to be replaced.

Before you take the dash off, try this: Remove the cover under the glove box. Remove the 3 screws that holds the fan motor onto the blower housing. Pull the fan motor down. Look for the rodent, or a nest. Look up, to see if a cabin air filter is installed, remove it & clean/replace. It would be very difficult for the rodent to get past the A/C evaporator & into the heater ducts, as they enter first thru the fan area. The fan usually traps the rodents.