Fan Speed #4 not Working

[lazabby]

The AC fan speeds 1-3 seem to work fine but when I turn it to the highest speed (#4) it doesn't blow. I remember reading about this problem years ago on this forum about this problem but I can't remember what the cause and solution was.

[Bitsyncmaster]

Speeds 3 and 4 are powered by relays. Most likely a pushed pin in the relay socket or a failed relay. Those two relays are the third and fourth one from the center of the car.