Interior fan/blower problems

[Gregb7488]

Hi, I’m having issues with the interior blowers on my wife’s 2007 jazz sport.
A few weeks ago the fans/ac stopped working, the digital display was on but nothing working.
I did the usual fuse checks and there is no problem there. After a bit of research I replaced the blower motor resistor, now the fans are permanently on high speed and cannot be turned off or down.
I did more research and changed the relay for a brand new one and replaced the cabin filter. None of these sorted the problem. Since then I have also replaced the blower motor itself in case that was causing the resistor to blow and fitted 2 more resistors and still the fans are constantly on.
I was advised to check the climate control switches too, once unplugged the fans still run 🤦🏻 I and also pretty sure there are no issues with the wiring
the only time the fans stop is when the ignition is switched off or the resistor is unplugged, but surely 3 of these can’t all be faulty. Can anyone shed some light on this as I’m now at a loss as to what to try next.
Thanks in advance

[CRC]

I've attached a graphic showing the wiring for the blower motor, and it looks a pretty simple system as car wiring goes.

Your fault suggests that the heater blower switch may well be the culprit, as, if that switch is in the 0 position, then there should be no route to ground for the blower motor, regardless of anything else.

For the blower motor to run, it must have a route through that switch to get to the vehicle O volts (ground) or no current can flow, and therefore the motor will not run.

[CRC]

Also, I'm not sure what you mean when you say you've replaced resistors?

The wiring diagram indicates that there are three resistors for switch positions 1,2 and 3, and position 4 lets the motor run with no added resistance.

Were these the resistors you're talking about?

These resistors are known as "ballast resistors" and tend to be physically quite large as they are flowing the full current that is flowing through the motor. They actually act a little like an electric fire element - they don't glow red hot, but they still tend to get quite warm and often come with aluminium cooling fins.

If you didn't get the right resistors for the job (and I'm not sure where they physically live) it's possible that there's a heat related wiring issue in that area?

Having said all that, I've now re-read your post and think you might not be talking about the blower fan ...... though in our 2003 Jazz, I know that the AC doesn't start up unless this fan is running. Please clarify....

[Gregb7488]

Hi thank you for the diagram, the car has the digital control switches, when I unplug the switch panel the fans still run. The resistor I’m talking about is maybe more a transistor (maybe I got my terminology slightly wrong) it lives under the dash just to the right of the blower motor it’s self. And once this is unplugged the motor stops.if I press the a/c button you hear it kick in under the bonnet but no change inside the car

[CRC]

A transistor is generally used as a solid state relay and comes into it's own when fast switching is required, for example, when the ECU is switching the coil packs on and off numerous times a second.

Our car only has a 4 position blower fan speed switch and an AC switch. If this is pressed then the AC only comes on when the blower fan is running, with the fan speed a function of the ballast resistor value that is now in series with the fan motor.

You need to find how the fan current is routing to ground ..... normally through the switch, but in your case ....

[Gregb7488]

Ok I will have to look into this. I just find it strange that the original problem was that the whole blower system stopped working completely and I researched possible causes, and what was described as the blower motor resistor was the probable cause. Once I replaced it the system works again but now won’t adjust or turn off unless this resistor is unplugged 🤷🏻

[TnTkr]

I would think that the new resistor or transistor was faulty. In another car I have there are two transistors in the fan speed control circuit board, and when they fail the fan runs at max speed just like you described.

[Gregb7488]

Ok, where are these located, the one I have replaced 3 times is in the plastic housing under the dashboard just to the right of the blower motor itself. Has a 4 pin plug coming from it to the wiring harness

[TnTkr]

The diagram describing your car with digital control switches is essential to find the problem. The diagram posted above is for conventional rotary switch speed control, and it does not help in your case.

[Gregb7488]

Yeah I don’t think I mentioned it was digital in the original post, I just need to sort this now as the wife has gone through 2 heatwaves now with constant warm air circulating round the car 😂

[CRC]

In the diagram posted, you can easily see how the system works with the manual switch.

Position 0 - there is no ground connection and the blower does not run.
Position 1 - three resistors are connected in series ( the resistance values are added together when in series) so there is maximum resistance, minimum current and the fan runs slowly.
Position 2 - two resistors connected in series so fan runs faster
Position 3 - one resistor in series, fan runs faster still.
Position 4 - no resistors in the circuit so fan runs at maximum.

I've looked on eBay and there are pictures of these resistor blocks and they seem to have 4 connectors and an open cage at the rear, and this opens cage would allow air to flow and cool the resistors.

The chances of having three faulty resistor units are vanishingly small, so the problem is somewhere else.

If it was me, I would take a multimeter set to resistance (ohms) and measure between the 4 pins of the resistance unit.

1-2, 1-3, 1-4 then 2-3, 2-4 and finally 3-4.
Produce a sketch of what you find see how it compares with the posted diagram. It should make sense and be the same.

I don't know how your " screen display" unit works, but it's bound to do something similar to the manual 4 position switch, but the switching will somehow be done electronically.

That is most probably where the issue is.

Electrical fault finding on 12 volt system is mostly about understanding the circuit, measuring voltages and resistances and concluding where the problem must be.