fan motor won't run on high

[Rickey]

The heater / ac fan won't run on high speed all other speeds seem ok. Does anyone have any ideals.

[hootz]

if your truck is a/c equipped it will use a high speed relay. There will be a fused wire to the relay that is the feed for high speed. this fuse will be inline and usually within 12-18 inches from the relay. if the fuse is good and the connection at the relay is good make sure you are getting power at the relay from the switch in high speed with the key on and selector on heat or a/c. if you have power at the battery feed terminal and the ignition feed from the switch in high suspect the relay itself.

[Stocker]

When my high speed quit, it turned out to be a bad switch. My local NAPA had one.

[Mint68]

Mine has been acting funny. When I would switch it to high it would blow lower than the medium speed; but when I would push it up just a little it would kick back to high. I pushed the connector and wiggled it then it sliped on more. Fixed the problem; hopefully this is your problem, it is dirt cheap to fix.

[wzuke]

Mine had the same symtom - new blower switch fixed it.

[Hutch]

Rickey,
Check the ground wire from the relay on the firewall.
It is very short
It is located up high between the glove box and passenger side wall.

There is a short ground wire that is supposed to go one of the shroud bolts that come through the fire wall
Easy test is to attach a short piece of wire while it is on high from the relay to ground.

A lot of folks do not get the ground re-attached correctly while working on the heater coil.

The symptoms are
Low= Low
Medium= Medium
High = Very Slow