driver air conditioner AC fan speed

[JourneytoRet]

Here's a puzzler. While working on a turn signal problem, I was running the engine and air conditioner (to get a break from the southern heat!). While I was sitting in the driver's seat enjoying a splash of cold air, the fan stopped running at setting 4. I thought I blew a fuse. But when I turned the a/c fan speed knob, speeds 1, 2 & 3 worked fine, but speed 4 didn't do anything. Anyone have some ideas on what to check?

[idroba]

There often is a relay for the highest fan speed which takes full alternator voltage to drive the fan at highest speed. You may have had a relay failure, or the wiring to it. However, the specifics of you individual rig are unknown to me. Just a general area to look into.

[JourneytoRet]

Interesting, but I guess I never thought about how a 4-position switch actually provides 4 different fan speeds. Anyone have any idea where such a relay may hide? I guess I'll look in the fuse box to see if it's fused as well.

[HowieE]

What chassis do you have?

Most fan systems use resistors across the fan switch do give different voltages to the fan motor. #4 is usually a straight 12 volt feed and not the one that fails.

Look at the fan motor housing under the dash. If there are 4 wires going to it the resistors may be inside the housing. If only a single wire than the attenuation is done at the switch.

[richinny]

at one time GM used a separate fuse for the highest speed on the blower. it was located in an inline fuse holder behind the alternator. i have no idea if your rig uses this system.

[NavyCorpsman]

Check the blower resistor. It is usually mounted on the air box in the engine compartment. It should have at least 5 wires on the plug. All vehicles have one, they just look a bit different. On occasion they are easy to get to.....

[m.hony]

Ditto on the blower motor resistor-

[masseyfarm]

On the 96 CLIPPER, the fuse for the high speed is located on the front bulkhead, access from the front outside. The is after the relay that provides a #10 wire direct from the Chassis feed to the blower.

The resistor assembly for the three lower speeds is located higher on the front bulkhead, access from the outside, direct behind the dash area and fused separately.

Dave

[JourneytoRet]

How Dave knows all this stuff about the Clipper is beyond me. I vote Masseyfarm to have 10 rivets.

[garypk]

If you have the 3 lower speeds that means the resistors are fine. There is a separate wire from the battery to the switch to bypass the resistor & give batt voltage for full speed. Ck the wire & inline fuse.