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Weird fan a/c switch problem

draffelt on Sun February 13, 2011 11:10 PM User is offline

Year: 2001
Make: Mazda
Model: 323
Engine Size: 1.6L
Country of Origin: Australia

On fan speed 1,2,3 the a/c works but the fan does not.
On fan speed 4 the fan does work, but the a/c does not.

Currently I can get both a/c and fan if I place the knob half way between 3 and 4.

Any ideas? The fan switch seems like the obvious choice, but a friend said it could be the 'relay'.

Any suggestions are much appreciated before I start pulling the dash off.

NickD on Mon February 14, 2011 6:46 AM User is offline

Sure would help to have a schematic, typically, the compressor is disabled with the blower switch in the off position so any contacts in the run position provide an enabling voltage for the clutch relay. High blower speed may use a separate relay where the lower speeds use the blower switch contacts directly through a resistor bank mounted downstream from the blower air circuit. Sounds like those resistors are burnt open. Only takes one as they are all in series to kill the blower at the lower speeds.

Would suspect both the blower switch and the resistor block, the major culprit is typically the blower motor, it draws a huge amount of current when first switched on, but tapers off rapidly once the speed builds up. If this motor is stalling due to corroded sleeve bearings, that is the culprit. Replacing the resistor block and the blower switch would only repeat this problem.

Cussboy on Mon February 14, 2011 7:24 PM User is offline

On the older made-in-Japan Mazda trucks (1986-1993), their blower motors were 2-wire, and symtoms exactly like this are the result of a bad blower resistor, typically mounted on the evaporator case.

mk378 on Mon February 14, 2011 7:37 PM User is offline

Yes the old system required continuity through the resistor to engage the A/C. If it is a resistor system check the fan area for mouse nests, etc. that can stop the airflow that keeps the resistor from overheating.

NickD on Tue February 15, 2011 6:41 AM User is offline

You mentioned a two wire motor that triggered some old memories, they were all two wire. First car I owned with a half way decent heater was a 48 Chrysler with a single resistor for a two speed blower. Prior to that like a 37 Caddy limo, olds, 41 Chevy, and Buick were all single speed with a two wire very repairable motor. Used propeller type fan and people would fight to sit in the right front seat. Anyone else, including the driver would freeze to death. Earlier cars like a 30 Ford or Olds, even a 33 Buick, didn't have any heaters whatsoever, but that is the way they were and were accepted like that. But you sure didn't have any blower motor problems with these cars, ha, didn't have a blower motor.

Alcohol was the standard anti-freeze, highest value of a thermostat was 160*F, any higher than that with an open cooling system, would evaporate. Was quite expensive too, with minimum wage of 75 cents an hour, ran about five bucks per gallon. Too rich for me, had to drain the radiator and block every night.

On minimum wage, still about the same, but everything else skyrocketed in price.

draffelt on Sun February 20, 2011 5:59 PM User is offline

Thanks a lot for your replies, much appreciated. I think it is time to buy myself a repair manual.

draffelt on Sun February 20, 2011 10:22 PM User is offline

So I managed to buy a copy of the 323 Protege manual which should be the same for my 323 Astina.

Here is a link to the A/C wiring diagram:

Here is some more info on the control system terminal labelling: and

Not sure if this offers any clues?

So I guess I should pull out the resistors first and check their resistance is correct? Then if that fails check the continuity of the fan switch?
And also check the sleeve bearings in the blower motor for corrosion as Nick suggested.

Thanks again!

mk378 on Mon February 21, 2011 8:44 AM User is offline

On this type of system, the symptoms you describe almost certainly mean the resistor is bad, and/or the connector to the resistor is burnt out. The resistor should be mounted attached to the ductwork just past the fan, usually behind the glove box.

draffelt on Fri February 25, 2011 9:47 PM User is offline

Hi All,
Thanks very much for your help. After replacing the resistor everything works fine.

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