Heater motor fan

[Jilldub]

When I bought the van, the heater motor fan wasn’t working so I can’t describe it’s failure mode.
 I guess I need to replace the fan motor, switch, and resistor?
 I have looked on Brickwerks and see there are 2 motors available for the t3 - Meyle and Febi. Are they interchangeable or do I need to strip my van before purchasing a new one?
 I understand people also replace the resistor with a PWM modulator,
Is this the better route to take and if so can anyone recommend where to purchase one from and what brand is best?
Thank you.

[ZsZ]

They are the same fan, just different brand - I am not sure what is the difference, they might were made in the same chinese factory. However there might be differences in sound level if they are not the same but different boxes.

IMO you need to change the switch and resistor just when they are faulty.

You may need a heater box foam kit - usually they are fallen apart. And some clips if the box was never opened before.

The PWM module gives you the possibility of stageless speed control - you replace the switch and resistor pack with it.
You can buy the cheap chinese modules form ebay/aliexpress, they are decent quality for the price - IMO the ones with the remote pot are easier to install. They need less butchering of the switch panel.

[Jilldub]

ZsZ
 My intention was to order the parts before removing the dash (hopefully to rebuild it the same day).
 I don’t want to take the dash out twice so do you know if the switch and resistor pack can be replaced with the dash in position?
If not, my thoughts were to fit a PWM as it seems a cheaper alternative.
Not sure if PWM performs as well as switch and resistor.
 I will order a foam kit.
Do you know how many clips are fitted to the unit?
Many thanks for your help.


 

[ZsZ]

You will need 11 or 13 clips according to BW. They say it depends on the heater box itself. I remember 13 on my '86

The resistor pack is inside the heater box so you cannot change that without removing the dash but you can access the switch by just removing the lever panel or from through the ashtray/radio hole.

The PWM controller pulses the full power which for the motor is like a voltage drop caused by a resistor. So if the controller amp rating is matched to the amp rating of the motor then it will safely replace the switch and the resistor pack.

[Robsey]

Apart from the switch, EVERYTHING else will need the dash panel removing.

As said - once the heater casing is unbolted from the van, it is likely that you would need to replace all the foam seals.

I did mine a year or so ago, and found that the matrix (heat exchanger / mini radiator thing) was okay.
I was also lucky that my casing already had the clips fitted.

I too fitted the PWM controller - but ensured that mine was rated much higher (amps) than a typical blower motor. Less chance of the pwm module dying than a unit rated close to the current draw of the motor.
Although - as most of these are made in China and obviously of various grades of quality.
It is good to mount the module somewhere easily accessible, rather than having to rip stuff out again if it fails.

The motor will only draw the current that it needs...so a higher rated PWM unit is perfectly safe.

As for how the PWM controller works, it turns the motor on and off in short pulses of full voltage.

The longer the pulse, the faster the fan motor speed.
As the PWM suggests it controls the width (duration) of the pulses - Pulse Width Modulation.

Obviously the resistor pack wastes battery voltage, which heats up the resistors.
Therefore more thirsty / wastefull on the battery demand than the PWM unit.

[Jilldub]

ZsZ.
Thank you for letting me know how many clips are needed, I will order them at the same time as I order the other parts.

[Jilldub]

Robsey.
That’s been really helpful.
I have decided to go the PWM route and have taken on board your comments

[Robsey]

ZsZ.
Thank you for letting me know how many clips are needed, I will order them at the same time as I order the other parts.

Is it not possible to look at the edges of the casing, to see if clips are already fitted?
Either through the ashtray hole and look from above,
or pull the lower plastic dash cover off its slides, and look from underneath-ish.

UPDATE - Expect to give it a good clean too.
They get very dusty over 30 plus years



But here is where you might see some clips...

[Robsey]

Looking at your first post...

I am assuming that you have checked all the obvious.
Or has the previous owner already reported a dead fan?

Fan not working.
On some speeds, or none of the speeds.

Some speeds - just top speed = resistor pack failure.

All speeds - testing order...
1 - Fuse is present, intact, and clean.
2 - Are you getting 12 volts at the "30" terminal of the fan switch.?
3 - when removed - can you turn the fan by hand.?
(Power off / take ignition key out).

[Jilldub]

Robsey.
Again, thank you for this information.
 I will check everything in order as suggested.
Unfortunately it will not be for a few days. 

[johnxl]

This is something I posted a couple of years ago, the PVM is still going strong (which is more than can be said for the diesel motor).

This is the one I used, you need one with 5 wires to the rheostat which allows the unit to be completely switched off (unlike the first 3 wire one I bought which always had a small draw). I removed and bridged the forward-reverse switch. Only fitted 4 months ago so I can't say how long it going to last.

https://www.amazon.co.uk/gp/product/B089DK89Z1/ref=ppx_yo_dt_b_asin_image_o08_s00?ie=UTF8&psc=1

[Robsey]

I used the original "blower switch" as an on off switch.

Position 0 = off.
Positions 1 to 3 = on.

All wires linked together to provide battery voltage to the pwm module.
My pwm rheostat is tucked in close to the glove box, out of sight, as it is rare that my wife or myself ever change the fan speeds.
On both of our cars, the speed is set to position 2.



I have heard it suggested that you could set the three speeds that you want via the rheostat (assuming remotely mounted).
Measure the resistance at each of the three speeds.

Finally - wire in the desired resistance value for each speed between the original fan switch speed pin number and the return wire to the pwm module.
Voila - three preselected speeds and no hot wasteful ceramic resistor pack.
Note that the resistors for the pwm speeds do not need to have a high wattage / current rating as it is a control circuit, not a motor feed / return circuit.

UPDATE - Hot off the press -
PWM Module with speed resistors instead of variable resistor.



Note however a separate isolator switch would be needed to turn off the supply to the PWM module.

But - as such, the module should only be live when the van is running. (Ignition live - not cranking. X relief relay fed circuit).

[Jilldub]

Checked the fuse. A 10 amp was fitted ( position 13) and blown. Previous owner had left several other 10 amp a day 20 amp fuse in the glovebox also all blown.
Managed to view heater box which had no clips fitted.
Could not see fan to test if it was seized, is this only possible when removed from the heater box?
 

[Robsey]

The fan could easily exceed the 20 amp fuse rating if the bearings run dry - and or the motor brushes become worn, burnt or whatever...

Unfortunately, it IS only possible to feel how freely the blower motor can spin when it is removed from the casing.

It seems odd that the previous owner would continue to swap fuses (10 amp) if it has already blown a 20 amp fuse.

But - it does point to a fan that is getting stiff, thus drawing excess current.

[Jilldub]

Thanks Robsey.
It looks like I’m back to plan “A” and need to remove the dash .