Jdcrae

Lately, my truck has been acting a bit odd in regards to the heater. I have an 08 STX 4.6 with manual heat. When on the highest setting, think its the 4th setting, I can audibly hear the air speed change. It will sound like its on high, and then intermittently, slow down, almost as if I manually turned it down a notch. This morning, subzero morning, while idling behind a car, I noticed that my lights would dim every time fan speed would slow down. Any ideas on what would cause this? My battery is good, tested no problems. Alternator is a high output from a reputable shop, Ford large case, tested good as well. Is it possible the resistor is starting to go bad?

On a related note, has anyone else had the problem of when shutting off the heat or a/c, it literally sounds like the blower motor drops an inch in the box? Any time I shut mine off, theres a loud clunk noise as if something is falling. With no cabin air filter, access to see inside seems pretty limited so I have never messed with it, just shrugged it off. Any help is appreciated.

rubbinsracin

I had a 1998 Oldmobile Intrigue as a work car years ago and every time the blower fan would come on/go off it had the same symptons you have described. They replaced my motor/squirrel cage fan and it was all back to normal.

However, you can find a resistor for our truck for like $15-$20 so it would be worth giving that a shot first.