Polo Mk10 2019 Fan Resistor Pack

[johntheo]

This is the battery current as measured by VCDS, negative when engine off (but ignition on) and positive with engine running (charging) but meaningless then for load measurement as the alternator is supplying all the electrical loads + the BMS managed charging rate.

IDE01836 Battery current -4.645 A

 

[sxdave]

I found this (

) on youtube - testing and disassembling a fan blower resistor from a skoda. Early on in the video the resistor values can to be 2.25 ohms, 0.85 ohms and 0.3 ohms. Later in the video, after destroying the part the conclusion is that the resistors are in series. The resistor values are similar to the you have measured. So taking the values from the video 2.25+0.85+0.3=3.4 ohms and the current you have for the slowest speed setting (3.9 amps) I get 13.26 volts, almost no voltage left to run the fan motor. From this I conclude the current readings must include some other users (probably various ECUs and associated peripheral sensors/actuators).
Also of interest is that the resistor pack has a thermal fuse that blows on overheating. The partial cut diagram you have also indicates the presence of a thermal fuse. I suspect this may be what fails in your case.
Another thing you mentioned is that the pack is wrapped in fabric. I wonder what this fabric is and if it should be present in operation (removed on installation?).

 

[johntheo]

This is what I come up with, probably incorrect. (Table 1) as the fan power will scarcely have such a jump from full speed 4 to speed 3.
The fan speed control has a 30A fuse and speed 4 is the only speed that will restart the engine (stop/start) even after a hours run so the current draw must be pretty high?

If you compare just my resistance readings (which are as shown) in Table 2 below, how does this fit with the U tube diagram and which terminal is no1 from left, are the terminals (u tube) 1,2,3&4 or 4, 3,2&1. My resistor had the terminals numbered and that's how I probed them so resistance readings+probed terminals are as shown.

Also have a look at electrical diagram in post #1.

Fan	Resistance	Circuit	Resistor		Resistance	Fan	Fan	Fan
speed	Ohms	Amps	watts		Vd	volts	Watts	Output
4	no resistor	17	0		0	12	204	100%
3	0.6	10.8	70.0		6.48	5.52	60	29%
2	0.9	6.2	34.6		5.58	6.42	40	20%
1	2.3	3.9	35.0		8.97	3.03	12	6%

Spare Resistor New
1 to 2	2.3	ohms
1 to 3	0.9	ohms
1 to 4	0.6	ohms
2 to 3	1.7	ohms
2 to 4	2.6	ohms
3 to 4	1.1	ohms
probe to probe	0.2	ohms

 

[telectrix]

replace the pollen filter. if it's blocked, the reduced airflow may be causing over heating.

 

[johntheo]

This was done after 2nd replacement and the old one looks in pristine condition compared to the ones that I change normally in other cars (every 3/4 years) with ~ X 5 times the mileage.

 

[brianmoooore]

You need to get an accurate value for the motor's current consumption, by connecting a DC ammeter in series with the feed to the motor or the resistor pack.
If the fan has it's own fuse, can also be done there, by pulling the fuse and connecting the meter across it's socket.

 

[johntheo]

Found 30A fuse but this only supplies the Blower control unit (J126) and only draws 1.58A at all blower speeds.

 

[johntheo]

Took another set of readings today but included the Alternator output, speed1 & speed2 with engine running don't make a lot of sense. One interesting point I noticed on speeds 3&4 is that the fan consumes ~ 2A less when blowing air through the heater matrix, presumably due of its resistance reducing the air flow.

20/03/2022​	Engine OFF​		20/03/2022​	Engine ON​
​	Battery​		​	Battery​	Alternator​	Battery​
Engine Off​	Amps​		Engine On​	Amps​	Amps​	Volts​
speed 0​	-4​		speed 0​	4​	5.5​	13.50​
speed 1​	-8.6​		speed 1​	5.3​	7.4​	13.46​
speed2​	-10.9​		speed2​	4.9​	9.2​	13.45​
speed 3​	-15.5​		speed 3​	4.5​	17.5​	13.44​
speed 4​	-21.7​		speed 4​	4​	26.5​	13.40​
	Fan Amps (calc)​			Fan Amps (calc)​
speed 0​	0​		speed 0​	-2.5​
speed 1​	4.6​		speed 1​	-1.9​
speed2​	6.9​		speed2​	0.3​
speed 3​	11.5​		speed 3​	9​
speed 4​	17.7​		speed 4​	18.5​

 

[johntheo]

You need to get an accurate value for the motor's current consumption, by connecting a DC ammeter in series with the feed to the motor or the resistor pack.
If the fan has it's own fuse, can also be done there, by pulling the fuse and connecting the meter across it's socket.

Took fan power readings from family 17 year old Polo (with original resistor pack), readings almost identical to present Polo, so would think "fault" elsewhere as I am now hearing of others with same problems.

9N Polo (2005), readings via M.meter. 3.7/6.3/10.2/16.2 (amps)
Mk 10 Polo (2019) , readings via VCDS. 3.9/6.2/10.8/17.0 (amps)

 

[johntheo]

I do not know how VW do this but on other makes I have seen the resistors are in a daisy chain so that:-
The slowest of 4 speeds uses R1 + R2 + R3,
The next slowest uses R2 + R3,
Next uses R3,
Fastest uses no resistors.
With this setup a failure in R3 causes all but fastest speed to fail.

Just for interest, I removed my resistor pack today and this is how the resistors are utilized, exactly as you have shown on utube. (terminals 1 to 4 from left to right)
speed 1, term. 2 to 1, R2+R3
speed 2, term. 3 to 1, R2 only
speed 3, term. 4 to 1, R1 only
Can't fathom why all three speeds fail together, R2 must fail to make both speed1 and speed2 fail together but speed3, is fed from term 4 to term 1 via the fusible link and R1 so one of these must also fail at the same time as speed 4 is the only one available once the pack fails.
Also term 1 (common) which goes to the fan via the fan switch becomes live (12V) once speed 4 is selected, don't know what this is for as the fan is fed directly from the fan switch (speed 4) and the fan runs on speed 4 with pack terminal block removed.

Also, would be grateful if someone can point me to a (mail order) motor factors as I just can't source a spare anywhere except the main dealers at £100, even mister-Auto sent me the wrong one as the (proper) code 2QO.959.263 seems to look for the wrong type.