Mazda Protege Fan Detection Circuit Fix

This page is a how-to guide for applying the solution for the "Flickering Fan Speed" which was presented here: Mazda Protege Fan Detection Circuit Analysis

Materials

The only thing you really need to do this are two resistors that are close to 470 Ohms (yellow-violet-brown) and 200 Ohms (red-black-brown). I'll list everything I used just for the sake of completeness.

Materials:

• 1x 470 Ohm resistor (1/4W or greater)
• 1x 200 Ohm resistor (1/4W or greater)
• 2x Small/Red crimp-type butt connectors
• 1x Small/Red solderless quick splice connector
• 3x 20cm length of hook-up wire
• 1x 10cm length of 1/4" heat-shrink tubing

Tools:

• Soldering Iron
• Wire cutters/strippers
• Crimp tool
• Small flat-head screwdriver
• Radio removal tool (made from a coat hanger)

Instructions

These instructions are merely the process I used, feel free to get creative.

Prepare the resistors

Attach wires, solder, and trim

This is the colour code I used for my wires:

• Black - Ground
• White - Input
• White/Blue - Output

Add some heat-shrink to isolate everything

Tape works just as well...

I pre-crimped and labelled my connectors to make sure I don't mess up

A quick primer on how to remove a stock Protege radio

Remove the plastic covers on either side of the radio.

Insert two bent pieces of coat hanger wire into the holes as shown. You'll feel them lock in place when you get far enough (don't be afraid to force them in there). Push your tools towards the doors while pulling out and the radio should just slide out. You might not get it the first time, but when you do you'll be able to steal a stock radio in less than 15 seconds ;)

Remember to remove the antenna and main radio harness connectors before proceeding.

This is the wire you're going to cut (Blue/Yellow)

It's much easier if you remove the connector from the back of the climate control unit to give yourself more room to work.

Cut and strip the wire

Try to cut away from the connector ... just in case you make a mistake.

Connect the circuit you made previously

• Connect the "output" to the wire that's still attached to the connector (the right butt connector).
• Connect the "input" to the wire that's buried in the harness (the left butt connector).

Connect your ground

Not very surprisingly, the black wire in that harness is ground. Splice into it or use any other bare metal to make your ground connection. I used one of those fancy solderless quick splice connector's just because I had some handy.

Enjoy some A/C at a proper fan speed

Seriously, 3 is the best speed.