!993 Ranger Heater switch won't change

[sacred77]

I replaced both the center turning switch which has (cold to left) and (hot to right), and the module just above the element.

Still no activity on the switch itself.

It is electrical and is sending no signal. Checked all fuses.
Truck just blows cold. all other things like heater hoses and core are fine.

Thanks for your help, blane

[Selectron]

If you have an electrically-operated blend door, as distinct from a cable-operated type, then you should find an electrical connector with three wires on the back of the temperature selector control knob. Those three wires will connect to the blend door actuator, and there's an excellent article here which explains how to test the system.

I'm not familiar with your vehicle so I can't help with component locations, but if you follow those three wires from the control knob, they will lead you to the actuator.

This is the wiring diagram for the '97 Ranger, which I notice has a '95 date on it, so if it applies to the '95 and if you're lucky then it might also apply to your '93. Check and see if the three wire colours match up with the diagram, which shows grey/red, dark green/orange, and yellow/light green. Even if they changed the colours between '93 and '97, you should still be able to make a diagnosis by following the testing procedure. Let me know if you need any help in interpreting voltage readings, etc.

P.S. Bear in mind that it might not be an electrical fault - it might be a mechanical failure such as a damaged blend door, but that's all covered in the article.

[99MBSport]

Rangers are notorius for having the blend door break at the top pivot point. See the motor/relay itself has a 90 degree swing BUT the area where the door opens and closes is something like 78 degrees. That means that when you close the heater switch to cold the door hits the box opening and puts pressure against it.....and the same with the other way. Therer are several good articles on this forum about the FIX....I did it by using a dremmel and slicing the bottom of the heater box off where the blend door is and put in a new blend door ($10.99). You can epoxy the heater back together and its as good as new................and you don't have to pay $800. to have a mechanic do it.