Hi All

Long time browser first time poster.

Have a weird and annoying issue, my interior blower Motor runs at 100% with or without the ignition on and it happened whilst i was driving so had to pull over and pull the power cable as there was a burning smell. I've replaced both the Blower and the Blower Resistor with the following last Friday:

Blower Motor: https://www.auto-doc.ie/nrf/13865402

Blower Resistor: https://www.auto-doc.ie/hitachi/15894358

I replaced both parts as my blower motor would have a mind of it's own, it would turn on sometimes and then turn off, when I took it off i found the Blower appeared to be slightly burnt and the Resistor had a burnt smell. In the week I've had a properly running Blower it has been ramping up and down occasionally, I only use 2 fan speeds, 3 or 6.

Have i just got unlucky with the resistor? or has my heater control unit gone?

Appreciate any help especially as I'm due to head away for the easter weekend

The other thing to consider is that the temperature/humidity (optional light) sensor might have failed. Non-FL MK3s have a sensor behind the mirror that often fails (common Golf problem too). I think the strategy might be that the fan motor runs higher than normal to compensate for no sensor information. If that's been the situation for a while it is likely you have burnt out your blower motor and/or the Heater Control/Climatronic unit in the process. A full code scan will reveal this.

I don't have any sensors behind my mirror, i just have a basic mirror and heater controller, it literally has AC, Rear defrost and Recirculate air, from what i can tell it is an OEM Part number 5E0820047D.

Regarding the initial fan stopping it was only 2 weeks prior to it being replaced, and the fan running at full power only started today.

Quick update:

I've managed to obtain an electrical drawing for the MK3, from this it appears that the high pressure AC sensor feeds the switched live input to the blower resistor when I pulled the connector off there was a very audible click. After this I metered the switched live without the ignition on and I was getting a variable voltage of about 8.9-9.3 volts, I was expecting this to be 0 volts.

After doing some further research from other forums it would appear that the fan uses PWM control which would explain the fluctuating voltage, my understanding of PWM control would be that the rotary switch would affect the voltage value am I wrong on this?

I have an OBDEleven on order but won't have it until the weekend courtesy of Easter, will provide another update when I can do a scan.

Update:

I finally have the OBDEleven scanner, I've finally got a code B10BE31. From Googling it appears to suggest the Blower Motor Controller, I'm assuming it's referring to what is called the Blower Resistor (J126 Module), am I right? If so did I just seem to get unlucky and get a bad resistor? or is there something else i should look for?

is there any resistor I should get? I thought buying a Hitachi would be good as they're a reputable brand, should i just get the OEM Bosch version? also has anyone bought anything from Skoda-parts.com?

4 hours ago, CianKT said:

Update:

I finally have the OBDEleven scanner, I've finally got a code B10BE31. From Googling it appears to suggest the Blower Motor Controller, I'm assuming it's referring to what is called the Blower Resistor (J126 Module), am I right? If so did I just seem to get unlucky and get a bad resistor? or is there something else i should look for?

is there any resistor I should get? I thought buying a Hitachi would be good as they're a reputable brand, should i just get the OEM Bosch version? also has anyone bought anything from Skoda-parts.com?

Even though it's called a resistor it's not actually a resistor but an electronic module that uses PWM to control the motor speed in a way that doesn't dissipate lots of heat.

Update:

Finally received an OEM Bosch unit from skoda-parts.com, great price and fast dispatch but seriously deceiving delivery time frame, used FedEx 2-4 business day, ended up being 9 business days.

Resistor/Controller has been replaced, fan is no longer running at 100% all the time and I can vary the speed and there's no codes, I will test it for a while and rescan and come back.

After disassembling the old Hitachi/Huko unit it smelt of burning. Hopefully it was just an unfortunate luck of getting a bad unit.