Hopefully i dont have to remove dash.better yet, how do i keep them out and how do they get there in the first place?

Access the blower from underneath the dash in the passenger's foot well. Motor sticks down... only 3 screws. Be sure the resistor block which sticks up into the air flow isn't clogged too, wired to blower. I'm betting on mice. The cowel drains are behind the hood hinges. Stuff SS steel wool (pot scrubber) up from underneath. Any water will still drain through but critters can't get access. It's almost time for mice to be having babies.

while you have the fan out make sure it spins freely, if it gummed up replace it $50 from advance. also inspect resistor if it is cracked replace it $35 advance. mine was so gummed from dirt it kept blowing the resistor and after the second one the guy told me to check the fan... the damn thing barely turned with my hand and was basically ruined. the squirrel cage comes off and goes on the new fan. took bout an hour to do both.

Catch some field mice in a live trap and let them loose in the cab and wait for a week or so, by then they will have been in there and chewed it up into smaller pieces and when you turn the fan on high it should blow out the vents, just make sure you are going down the road at a high rate of speed and have the windows down before turning on the fan, this will help vacuum out the debris as it flies out.:lmao::lol:Sorry couldn't resist.

W&F your just so funny...:lmao:But seriously the blower motor is just easy to pull out and clean.

Sorry Mike, I disagree! Better to keep the mice outta there. It really stinks with dead mice in there, unhealthy breathing mouse rot & if they jam the blower motor, you can fry it... At least my neighbor did on a new Saturn. Warentee does not cover rodent damage, please pay the cashier! He & I then screened his air intake. Also, leaves & mouse fluff can clog the heater core air flow & is a beach to remove. The same stuff can block the resistor... protrudes into the ductwork where the airflow cools it. If covered by mouse fluff, resistor runs hot & fails. So short term take out the 3 screws & clean the bird cage. Long term, sceeen or block with the SS steel wool the cowel drains behind the hood hinges. Problem permanantly solved. I used the SS pot scrubber my first year with this truck... brand new... 12 years later, no mice in the cab, despite them trashing my under hood insulation.