Motor configuration help

[SJones]

I am trying to work out how a motor works, I know some basic electrical principles but I'm a little confused as to how this motor works (or to the reasons why it is set up the way it is)

The motor is from a car's cooling system, the part I am a bit confused with is that it has 2 posotive and 2 negative terminals in combination with 3 relays to control speed.

here is the wiring diagram

here is the connection diagram and amp rating


my confusion is why 4 connectors (specifically 2 negative)? in the low speed configuration it only uses 2 of these connectors, so my guess is one of two things, there is some sort of reistors on the motor itself (as there is nothing in the wiring diagram before the motor) to control the amps - this would probably make the most sense. OR the motor is a compund motor but this seems overly complicated for a fan motor?

Any thoughts on whats going on here?

 

[Kabelsalat]

This might be an obvious question, but I know some cars do have double cooling fans in front. My old (now scrapped) X-trail was one such car.
So the question: Does your car have two separate fans ?

Otherwise : What car model is it? Can you post an image of the fan and especially the connection points and any labels ?

 

[SJones]

Its a 2006 mazda mx5 (miata) and its only got one fan, the fan is burried deep into the bonet (its at an angle and has stuff like battery, ecu. power steering tank, washer fluid tank and other stuff ontop)

however this is the picture from an ebay sale of said fan

as per the second image in the first post there is 1 connector, 4 pins, this can be seen centre, top of the motor in the above picture

 

[Minder]

Two possibilities, one is a DC motor with wound field, the second, a ECM electronically commutated motor.

 

[SJones]

Two possibilities, one is a DC motor with wound field, the second, a ECM electronically commutated motor.

Thanks for the info, but from my understanding, don't both circuits in those types of motor have to be active at all times for it to work?

If the above statement is incorrect, have you got a link to how these work (all info I have found on wound field motor imply that both need to be activated as there are no permanent magnets and for a ECM wouldn't there need to be at least 3 connections at all times?)

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This was my thought on the way it works
if you look at the second picture in the first post
if its on the slow setting then only 1 circuit is made ( Connector C (positive) & B (negative)) this looks to be a standard DC brushed motor as it doesn't need anything else to run.

But the middle speed, the relay activates and connects a second negative connection (according to the wiring diag) and now draws more current,
This is where I thought there would be some sort of resistor comes into play, all located within the motor/fan assembly, one on the connector C and another on connector B at some rating higher than connector C
When both B&D are connected it gives the maximum output of the the resistor C.

Then when in high speed, with both circuits activated it draws the full amps the fan can use bypassing the resistors on C&B connections and flowing unimpeded through connectors A&D?

 

[Kabelsalat]

Without detailed knowledge of the fan motor itself, it's a guesswork at best.
Since the relay arrays is arranged in such a way there are two for +12V and one for extra ground AND that the relays are marked "fan 1" to "fan 3" there may be one of, or a combination of:

• The fan symbol is actually 3 different fan motors (why else should the relay boxes says "cooling fan1" to "cooling fan3" ?)
  
• The fan is only one, but the relays are arranged in such way that one or more criteria (a logic function of such, typically one or more sensors) must be met in order for the fan to spin.
• One set of relay for "full sped" and another for PMW speed control.

That is - if the schematic actually are representative for your car model. .