Weak fan

My heater blower seems to be related to engine speed. Even on HIGH, I can’t even hear it when idling. I can’t actually hear when driving either, because I drive a Jeep Wrangler, mainly on gravel roads, and I can’t hear much of anything. But I can feel it blowing when I am cruising along. The switch to make it come out other places seems to work just fine. How does the engine speed affect the blower motor speed?

Can you hear the fan when the car is stopped and idling? What happens when you change fan speeds?

If I had to guess I’d say that your fan is probably not working at all. When you’re driving along your movement is pushing air in through the fresh air intake. To find out for sure, leave the fan off, turn the key to on without starting the car, then turn on the fan. If you get no noise and no blowing air then your fan is dead.

If so then the first thing to do is check the fuse, though if it blew you’ll need to find out why since it will keep blowing. If the fuse is ok then you need to start checking the whole fan circuit to find the problem. It may be as simple as a loose/corroded connection. It may be that you need a new fan or new switch. You’ll need a voltmeter to check the various elements.