My heater fan only runs at high speed. I just replaced the fan speed switch on the dash. The fan still only runs on the high speed. What else can I check out.
Thanks for any help.
R J F

 

I forgot to put in year of truck it's a 93 inline-6 auto no ac

 

Check the blower resistor. When it fails, you will only have high fan speed.

Good luck!
Scott

 

Scott thanks for the info. Is this located under the dash or under the hood? Also an idea what it looks like would help.
Thanks again,
Rich
R J F

 

Usually inside the fan housing - a short coil of resistance wire (or 2 coils if multi speed. Mounted on a little insulator in the air stream. Some of them are on the back side of the electrical connector to the fan motor (if the connector is mounted to the housing and not the motor), and can be reached by taking out the connector mounting screws. Your mileage may vary.

 

Thanks alchymist, I'll check that out.
Rich

 

Text book resistor.

Look above the exhaust manifold, as close to the firewall as you can get... just as he said above.

EZ fix.

 

I 'm going fishing tomorrow (Stripers in Cape Cod Bay) so I'll check this out on Saturday. Thanks a lot for all the info.
you all have a great day
Rich

 

Hi,

Had similar problem. My mechanic neighbor suggested checking the blower resistor - he was right. Had to find it - inside the passenger compartment ('99 F150 SuperCab), under and a bit in front of glove compartment, beside the blower motor.

Chunks of the resistor assembly were corroded. Bought replacement from Ford dealer (part no. 4L3Z-19A706-AA, under $25 Cdn).

Watched it in action, while connected to the wiring harness, outside the blower duct (?). Two of the resistors operate red hot when the blower was running on the first 2 low settings of the blower speed dial. Mounted it in its place. Seems to be working OK. But, have a feeling it will need replacing in another 4-5 years from now.

Good luck on solving your problem.

 

Thanks to all who replyed. I found the blower resistor in my 93 it was under the hood in the heater duct work next to the heater fan. I took it apart and I'm waiting for a part to arrive from ford. Thanks again all.