My 1997 Ford Ranger is a 2.3L and has been a great truck for all 320,000 miles. Recently my blower stopped blowing. I have replaced the dashboard switch, the blower motor, the resistor coil, and the relay switch. Unfortunately still nothing. When I remove the relay and use my volt meter, I get 12 volts across all the terminals. When I remove the 40A fuse I read 0.01 volts across the terminal (the fuse looks fine) - this doesn't seem right. Using the volt meter at the plug that plugs into the blower motor I get nothing. I get nothing on the volt meter at the plug for the dashboard switch either. I'm out of options, I don't know what else to check. I've seen other threads regarding blower motors, but my problem seems to be unique. Any help would be very much appreciated!

 

Welcome to the forum

Fuse #6(7.5amp) in cab fuse box powers the Blower Relay

The Blower motor fuse(40amp) sends 12v to blower motor when Relay is Closed(grounded)

The whole blower control system is Grounds, not 12v
Blower motor gets 12volt directly from Blower relay, then it needs a Ground to start working.
If you have key on and selector on anything but OFF then motors Pink/white stripe wire should have 12volts, that means blower relay is CLOSED
If no 12v then blower relay is not closed, check fuse 6 in cab fuse panel
Speed controls in the cab are Grounds for the resistor block

 

First, thanks for the system description, that helps a lot! OK, so put my volt meter ground on the battery terminal and the positive on each side of the fuse. I get 12V across the fuse at all times (regardless of fan speed switch position). At the blower motor, again I put the ground on the battery terminal and the positive on the pink/white stripe wire. I read 0.2V all the time (again regardless of switch position). So based on what you said below it sounds like the switch is not grounding the system properly to allow the relay to open and provide 12V to the blower? Does that mean that the old switch and new switch I bought are both bad?

 

And did you check Fuse #6 in the cab fuse box?

This fuse powers the Relay that powers up the Pink wire
No volts on pink wire means relay is OPEN

Fuse #6---------------Blower Relay-----------Cab select switch------cab ground

Blower fuse------------Blower Relay-----(pink wire)---------blower motor--(resistor block)-----Speed switch---------cab ground

Here is the diagram

 

OK. So fuse #6 in the cab is working and has power. The 40A fuse in the engine compartment is hot. I have power on the red and orange wire at the switch. The relay clicks when I turn the ignition on (regardless of control switch settings). The posts to the relay are all 0 except for one that shows 12-14V all the time. Even when I remove the #6 and 40A fuse I still get one terminal of the relay that shows 12-14V. Could it be that I have a short that keeps the relay close all the time? Below is a diagram of the terminal the relay plugs into along with the voltage reading I get from each terminal.

 

Are you sure your diagram is correct?

Lower slot above would be relay #85, the one directly above it running the same direction would be #86, these are the relays COIL terminals, they activate the relays when one is 12v and the other a ground, doesn't matter which is which, it just a coil of wire inside that turns into a magnet when there is 12v AND a ground
85 and 86 would be pins 1 and 2 in the diagram in first post
If you pulled Fuse #6 in the cab then that 12v should go off, if not you have the wrong relay

The other slot running the same direction but in the middle is #30 it part of the LOAD the relay passes, pin 5 in the wiring diagram

In the middle with slot running up and down is #87A, it would be Pin 4 if diagram had a pin 4, it is what arrow is touching in diagram
#30 and #87A are connected when Relay is OFF

On the far right is #87, no A, lol, it would be pin 3 in the diagram, #30 and #87 are connected when relay is ON

Now Ford or any car maker can reverse 30 and 87, but one of them should have 12volts from the 40amp fuse in this example

Picture of Relay numbering here: http://www.mobileinformationlabs.com...es/HowTo-7.gif

And no, no one in the wide wide world of sports knows why relays are number this way, story is Bosch/VW did it, but Germans are more clever than that, IMO, I think politicians did it, favorite numbers thing

German thing here: http://www.vintagebus.com/wiring/defs.html

 

Thanks for the feedback RF Veteran. OK, so time to back up. What I thought was the blower motor relay is Relay #5 in the under the hood power distribution module. It is labelled "WOT A/C Relay" in my owner's manual, but what you said above has me thinking I am looking at the wrong relay. The owners manual has a cryptic statement "...have alternate locations for some relays." So, can anyone tell me where the blower motor relay is located? We'll get there! I appreciate the help guys!

 

I think I found it. Is it up by the passenger side headlight?

 

 

Test if its the correct relay by pulling Fuse #6 in cab fuse box, key on, Slot #85 or 86 should lose 12volts

Yes, WOT(wide open throttle) Relay wouldn't be the right one for blower motor, this relay shuts off AC Compressor if driver presses gas pedal to the floor(WOT) so engine has MAX Power for passing or ??


EDIT:
You just posted the diagram

Key on, Pull #6 fuse in cab to see if #86 loses power, if so this this is probably the right relay

#87 is the Load power, should be Battery Voltage though, pull 40 amp Blower Fuse and 87 should lose power, yes it should have power 24/7(all the time)

#85 is a Ground when Heat or AC is ON, this activates the relay, most vehicle electrics are Ground activated, as it is safer to run ground wires around a vehicle than 12v wires

#30 should be the Pink/white stripe wire that runs to the Blower motor, when relay closes 30 and 87 are connected

87A wouldn't be used in Blower motor circuit

Concern is #87 and its low voltage, test voltage AT the 40amp fuse and retest that fuse
9-10v means there is probably no AMPs so it can't run the motor, a Voltage meter has no LOAD or Draw, so when you see a lower voltage, than Battery Voltage(12.5v), it usually means its just a "light" voltage, it has no AMPs for a load like blower motor, it will drop to 0 volts when connected to blower motor

 

Will give it a try tomorrow. Thanks again for the help.

 

Well I got sick and that delayed my plans a bit. Anyway, finally got back to it and thanks to all of your help, I finally figured it out. The problem was the relay box for the blower motor which is located just behind the passenger side headlight. When I disconnected it from the wall and took off the wire cover, I could see corrosion pretty bad. I pull on the wires and one popped off completely, it was the BLK/GRN wire that powers the blower motor. I was able to go to NAPA and get a harness connector which had the plugs for the relay and new wires. I just spliced the new wires into the exist, left the old box attached because it houses another small relay that isn't corroded. Everything works! So nice to have a blower motor functioning again.

So for anyone looking at this thread. My problem all started when my blower motor low speeds stopped working, only my high speed worked and it only worked for about a month before it gave up as well. Most people say that the problem is likely the Resistor assembly in this scenario and it may well be most of the time. That was NOT the case for me (although I replaced mine because it was a rusted mess). Thanks to all who helped, and good luck to those reading and using this thread. The attachment in the thread above from RonD was most helpful as it is the wiring diagram for the electrical circuit.

 

Good work

Thanks for posting the update and the FIX