The Final Stage Resistor is playing up in my recently acquired 2002 TD6 L322. So I ordered a new Britpart one along with some other stuff & installed it yesterday. Tested it outside the house & all was well. a little while later I had to go for a short drive (about 20mins) About 10mins into the drive the fan blower went on full & no matter what I did it wouldn't turn off or slow down. Even when I turned the engine off it wouldn't stop blowing at full speed, So I pulled the fuse, left it to cool down & swapped the old unit back in. As this is a LHD RR access is very difficult (I didn't remove the Glove Box or Fuse Panel) Luckily I had left the Resistor hanging down where I could get to it & had not replaced any panels, which was good as it was dark at the time.

Now having put the old unit back in I can hear a ticking, like a rapid clock. I assume I never heard this before as the resistor was hidden away behind all the panels. I can't be 100% sure its the resister ticking but it does go away if I remove it all together. If I plug the dodgy Britpart resister back in I can't hear anything because the fan is going at full blast.

Any idea what the ticking is? is it normal? is it because the old unit is failing? Or is something else failing that causing it to tick?

I just want to know whats going on before I fit another (genuine unit!) so all input greatly appreciated.

Cheers, Nigel

I would say your fan is seizing. That would cause the new FSR to burn immediately. Put the old FSR back and try pressing it from the connector side. If it then makes the fan spin, it means that the solders inside are gone due to high current.
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DJ

The resistor must be fitted into the airduct to keep in cool in operation. If you left it just dangling behind the dash it will overheat and burn out. The slower the speed the more current it is controling so will get hotter quickly.
I would try another cheap one but install it properly. Mine was a blue one!

Hmmm, Thanks for the input but not convinced. The original FSR still works but does weird things, the new one works too but only at full blast. I've got another new one coming on Monday hopefully that will sort it.

Both dj and andy are absolutely spot on with there advice.

The fsr is simply a bank of resistors that are switched into blower fan circuit to vary the voltage to the blower fan motor to vary it's speed.
The fsr drops the alternator /battery voltage to 8V for maximun speed and thereafter adds resistance to the circuit in stages down to 2V for minimum speed.

These resistors produce a great deal of heat hence the cooling rods attached to the body of the fsr.
The cooling rods are air cooled and to achieve this fully must be in a cool air stream, for convenience car manufactures tend to use the un-heated air stream into the blower fan to provide cooling.
It is imperative the cooling rods are in the inlet air stream to achieve the necessary cooling otherwise the fsr will simply over-heat and destroy itself.

A blower fan running on maximum speed irrespective of control knob setting indicates the fsr has failed for whatever reason but usually indicates it has over heated causing the resistors to fail / burn out along with the associated electrical connections.
The fsr in this situation is fit only for the bin.

As regards the motor being stiff to turn, this indeed can be a problem.
If the motor is stiff to turn it will take more current to run. This results in one of two things, either the circuit fuse blows or the fsr is subject to higher current which results in the component resistors significantly over-heating which cause the fsr to fail.
A stiff motor on another of my cars did exactly the above and burn out the comparable fsr, fortunately VW have the sense to install both the blower motor and fsr in positions which allow them both to be changed in a matter of minutes at significantly less cost than those in an FFRR.

As regards your problem, it may be a stiff motor causing your problems but I'm inclined to doubt it.
It is almost certainly fsr related.

The Britpart units are cr.p and only fit for the bin when you buy them.
Your original unit which is playing up appears to have partially failed causing the symptoms you describe.
I would be inclined to buy a genuine LR fsr, fit in into the correct position and I have a suspicion you problem will be resolved......for the life of the fsr. Unfortunately they don't last forever.

The FSR is NOT 'simply a bank of resistors', neither does it vary the voltage between 2v and 8v.

It is a collection of resistors and other electronics (probably Darlington pair transistor switches - this will be why the fan can continue to run on when everything is turned off, when darlingtons fail they usually go short circuit, and they are also prone to fail if overheated, e.g. run without the heatsink being in a good stream of cold air).

The 5 wires going to the FSR are as follows:-

Brown - Earth
Yellow / Green - Permanent 12v feed
Red / Green - to fan motor
Black / Green - to fan motor
Red - control voltage from HVAC ECU.

To check your fan motor is OK, remove the plug from the FSR, and short the pins for the Yellow / Green and red/green wires together (using a short loop of wire), similarly short the pins for the brown and black / green wires together - fan motor should now run at full speed. (if it doesn't, you either have a wiring fault, or it is cream crackered)

Using a voltmeter, measure the voltage on the red wire with the other meter lead connected to earth (ignition needs to be turned 'on' for this test).

With the blower control 'off' (no LED's lit), you should have 0v. Turning the blower control up one step at a time should increase this voltage by 1v for each extra LED lit up to a maximum of 8v if this is OK, all well and good, if not you have an issue either with the switch, wiring , or (rarely) the HVAC ECU.

If both of the above are OK, then your FSR is goosed - I will post a set of pin to pin resistance readings for a 'good' unit and a 'bad' unit here as soon asIi have time to collate them. (replaced my FSR last week due to fan continuing to run on with ignition off) 2006 (56 Reg) 4.4 V8 Vogue In Bonatti Grey (Gorgeous!!)

^"Bank of resistors" might be a slight simplification but that is what it essentially does.

Lot of important info in this thread.

Any news on fan still not working after replacement of FSR?

Sorry, but as a new member I need to post 3 times before I can send a PM to anyone on this thread with FSR problems…

I think the P38A pulse width modulation system was better. Ron B. VK2OTC
2004 L322 V8 Auto
2007 Yamaha XJR1300
Previous: 1983, 1986 RRC; 1995, 1996 P38A; 1995 Disco1; 1984 V8 County 110; Series IIA

Yes, bet you do. But do not help out on fan problem on L322…

I just fitted a new final stage resister. Now the fan speed dial only goes up to 6 and 7 won’t light up. What have I done? 😩