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View Full Version : Automotive electrical / electronic advice needed.



MJC
09-23-2004, 08:43 AM
Why would the HVAC fan motor up under the dashboard not run on anything but high speed?

This happened to me once before and I replaced the fan motor, which solved the problem.

The motor only lasts a little more than 2 years. Why does it keep burning out like this?

Is there anything I can do to fix the motor? It's still running, but not on any of the lower speeds.

FWIW - it's in a '99 Ford Contour.

Ken Hutchins
09-23-2004, 08:59 AM
Don't know about a Fud, but Dogs have a resistor gismo the goes to crap with the same result. The dog resistor is under the hood on the dash. Can you tell I'm discusted with fuds and dogs, so just got a me new Toyota.

MJC
09-23-2004, 09:22 AM
Would there be resistors somewhere in the fan motor itself?

High C
09-23-2004, 09:28 AM
I had a Toyota pickup (84) that did that, wouldn't run on the lowest speed, oh well. My Chevy (99)sometimes changes speeds all by itself, but I'm pretty sure that's a worn switch. The switchgear on my '97 Ford truck was superb.

flatbottom
09-23-2004, 09:30 AM
I have a 1998 GMC Savanna 140k miles. In the last 8k miles I have bought two fuel pumps at $500 each plus labor. a new heater fan at $98, a new alternator at $140 plus labor. waterpump, a new Oxygen sensor at $100. and the list goes on. ( it is in the shop today because it is missing at highway speed)

By comparison I also have a 1999 Volvo V-70 which is rated as one of the worst cars to maintain. It has 180K and the only thing I have had to do is change a light bulb evry couple of months and replace a $50 upper motor mount.

I wish Toyota or one of the Japanese companies made a full size van

SC-Lion
09-23-2004, 11:21 AM
As mentioned above itís probably the power resistor (assuming you donít have ACC- automatic climate control). Could be the switch as well, but the odds are with the resistor.

If you can get to them theyíre very easy to change out, but Iíve never seen one integrated into the fan motor. They produce, and need to dissipate, a fare amount of heat so they are usually mounted separately from the fan motor and somewhere under the dash that gets some air flow. My experience is with foreign cars so I donít know exactly what a Ford unit looks like, but it should be about 3 to 6 inches long and have a cross section (hollow round or solid square) of somewhere around .5 to 1.5 inches. Theyíre usually made of ceramic and very easy to spot when you see it.

If you can remember what a ballast resistor looked like on an old points and condenser car this thing is their cousin and looks similar.

-Gary

Kev Smyth
09-23-2004, 11:31 AM
Since the problem is recurrent I'd guess it isn't so much a design flaw as a bad connection or dirty switch. If either are questionable, the motor/resistor pack won't get the full designed voltage, and will run "hot." The extra heat will degrade the resistor(s) and cause it to fail.

When you replace it, work your way back through the circuit cleaning/checking all the connections and switch. A little contact cleaner from Radio Shack will help.

I'd also throw a volt meter on while the motor's running, headlights and fan on high, and check to see that you still have 13.7- 14.0 volts at the battery. It can be useful to check at other points in the system, such as headlights, too. If you find less, the real issue might be a compromised alternator or voltage regulator.

Good luck! ;)

Domesticated_Mr. Know It All
09-23-2004, 01:08 PM
On a Ford It's more than likely the blower switch. They are junk and frequently burn up, sometimes causing fires. Get the switch and also the plug with wires that plugs into the switch since it's probably melted too. I got a switch and the plug from a junkyard for a 91 Taurus, less than 5 bucks. The really hard part was getting the plastic dash panel off and back on without breaking anything. It took me all afternoon but it works on all 3 speeds now.
Hang in there. smile.gif