Blower pwm upgrade

An alchemy of sparks, copper wire and earth

Moderators: User administrators, Moderators

Post Reply
Lanciaman
Registered user
Posts: 180
Joined: 14 Nov 2010, 23:17
80-90 Mem No: 13785
Location: Cornywall

Blower pwm upgrade

Post by Lanciaman »

I've got my dash out at the mo, so am going to fix the blower motor and like the idea of the pwm upgrade.
But I can't find much about it, and Bw's, CVC and JK don't seem to offer them. Some of the reviews of the units on Amazon report early failure of the electronics, so I wonder if this is as good a mod to do as it might appear.
Can anyone recommend a unit that has proved reliable, and from where did you purchase?
(Also, have you seen the price of replacement resistors if you stay with the original set up...40/50 quid...for a resistor???).

User avatar
Robsey
Registered user
Posts: 1159
Joined: 19 May 2012, 20:45
80-90 Mem No: 11137
Location: East Manchester

Re: Blower pwm upgrade

Post by Robsey »

There are people for and against the pwm units.
The general rule of thumb is that if you want the pwm module to last, get one that has a current rating significantly higher than the motor's intended rating.

Sadly most pwm modules are cheap and sometimes chearful units from China.
Should I say - usually ebay specials...

The pro-pwm group will say that you use less electricity with pwm, and units are much cheaper to buy than a restistor pack.
You could probably buy three for the price of a resistor pack.

Also most pwm users locate the module outside of the heater box, and therefore it is easier to access and replace when the time comes.

Just ensure that you do not skimp on the wiring.

‐-----------------------------------------

The non-pwm group will have the advantage of a known, good reliable unit that will probably out-live the van.
Yes the resistor packs are expensive as a single purchase, but you may never need to replace it again.
Which is just as well, as not everyone enjoys ripping the dash out to access and split open the heater casing.
1983 Tin Top with a poorly DF and 4 speed DT box.
1987 Electrics and a DJ engine.
Maybe one day I might get it finished

johnxl
Registered user
Posts: 31
Joined: 26 Jun 2019, 07:22
80-90 Mem No: 16948
Location: Wales

Re: Blower pwm upgrade

Post by johnxl »

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

Lanciaman
Registered user
Posts: 180
Joined: 14 Nov 2010, 23:17
80-90 Mem No: 13785
Location: Cornywall

Re: Blower pwm upgrade

Post by Lanciaman »

I am not convinced this is a worthy upgrade. I think the fact that Bw's don't offer them tells you something.
I'm reluctant to install one of these units in spite of it looking like a good upgrade from a user point of view, but wanted to seek recommendations. Unfortunately the price of the resistor is a bit steep, and out of stock, so I am in a bit of a dilemma. Think I'll test the old resistor see if it's usable and stay old school. Bw's are always out of stock when I'm doing a job grrr. [E D I T - no they're not, it's the loom that's out of stock. But 40 quid! Hey ho]
Thanks for the feedback guys.

User avatar
Robsey
Registered user
Posts: 1159
Joined: 19 May 2012, 20:45
80-90 Mem No: 11137
Location: East Manchester

Re: Blower pwm upgrade

Post by Robsey »

Could be worse...
Heritage have the resistor and loom in stock for £72.
Youch!!

You are definitely looking at the front resistor pack for £40.?
That sound like the price for the rear heater resistor to me.

UPDATE -
Just checked - yes, it does look like the correct part.
Easy enough to crimp a couple of tight female spades onto the three legs. :)
1983 Tin Top with a poorly DF and 4 speed DT box.
1987 Electrics and a DJ engine.
Maybe one day I might get it finished

Lanciaman
Registered user
Posts: 180
Joined: 14 Nov 2010, 23:17
80-90 Mem No: 13785
Location: Cornywall

Re: Blower pwm upgrade

Post by Lanciaman »

I do like a tight female spade  :run

TONYT25T25
Registered user
Posts: 1825
Joined: 16 Sep 2013, 17:19
80-90 Mem No: 13596
Location: Hampshire

Re: Blower pwm upgrade

Post by TONYT25T25 »

My blower packed up a few years ago, preceded by an electrical burning smell then a bit of smoke and then no more blower, it had been squealing for a while.  Have been unable to remove dash since then due to a couple of screws seizing up and no amount releasing fluid releases them.  Have even thought about buying a 12v bilge ventilation blower and attaching it to the air outlets to see if they work in reverse and blow air to the inside of the windscreen.  Do not have a problem with demisting anyway due to the nature of the vehicles structure.
1984 Campervan 1.9DG Petrol WBX

User avatar
Robsey
Registered user
Posts: 1159
Joined: 19 May 2012, 20:45
80-90 Mem No: 11137
Location: East Manchester

Re: Blower pwm upgrade

Post by Robsey »

Although it is a slight detour from the main topic,
The screws that hold the dash on around the front are only self-tappers.

The only way is to drill them out when a No2 Philips will not grip.

Once the heads are drilled off, the dash can be removed, and then so can the heater assembly.

If it is 100% untouched since the factory, then the heater casing will be clipped and glued together.
Great fun in a masochistic sort of way... But there are plenty of youtube videos about that.

Once the heater is out of the way, it is possible to remove the remnants of the self tapping screws by gripping and twisting with a pair of mole-grips or similar.
That is how I did it on my van - a bit worrying at first, because I did not take the screen out and I thought one false move may cause the drill to go crashing into the glass.

Take your time, let the drill do the work, and you should be fine.
Accidents usually happen when you are pushing too hard on the drill, or simply rushing.
1983 Tin Top with a poorly DF and 4 speed DT box.
1987 Electrics and a DJ engine.
Maybe one day I might get it finished

User avatar
Splurt
Registered user
Posts: 484
Joined: 09 May 2011, 22:51
80-90 Mem No: 9694
Location: Co.Armagh Syncronaut #283

Re: Blower pwm upgrade

Post by Splurt »

Some good info here, wish I had have known about the 5 wire rheo vs the 3 wire when I installed mine!  I cut a hole to install the rocker switch for piece of mind that there is zero draw whenever not in use. 
I am very happy with it though.  If the PWM fails it is located just behind the panel below the radio that pulls off.  I soldered in spade connectors so that it can be a plug and play replacement if needs be.  For less than a £10 for the unit it would be my pick over a resistor pack, even if I do go through a number of them over the years.  
From reading up on the resistor packs, the slower fan speed requires power to be 'wasted' in the form of excess heat by current moving through the resistor coil.  If the fan is on full speed no resistance is required.  Without knowing this I would have always kept the fan on a low speed for some light airflow in the cab.  I still like to do this, but with the PWM the speed is reduced in a more efficient, less dangerous way, without having to run it through what is essentially an electric heater.
Here is what the internals of my heater box looked like on opening, too much charring for my liking....
ImageImage


 
Ryan

89 - 1.8T AGU - SA Syncro - Hightop Camper 

'I love my brick'
Fr Jack Hackett

User avatar
Splurt
Registered user
Posts: 484
Joined: 09 May 2011, 22:51
80-90 Mem No: 9694
Location: Co.Armagh Syncronaut #283

Re: Blower pwm upgrade

Post by Splurt »

I have my old resistor pack still, your welcome to it if you want it?  

My blower motor seized so it had been working correctly prior.  You would need to test it though to be sure

Image

 
Ryan

89 - 1.8T AGU - SA Syncro - Hightop Camper 

'I love my brick'
Fr Jack Hackett

User avatar
Robsey
Registered user
Posts: 1159
Joined: 19 May 2012, 20:45
80-90 Mem No: 11137
Location: East Manchester

Re: Blower pwm upgrade

Post by Robsey »

I did a slightly different take on this.

I wired my original switch, so that I could turn the supply to the pwm off - in the off position of course.

I then bridged speeds 1, 2 and 3, so that they all shared the output to the pwm module via one wire.

This retains the original look of the van.

My pwm module has the rheostat built into the circuit board - the rheostat has a positive click for it's own off position.

when I finally finish restoring the van, the pwm will probably sit behind the plastic trim, below the radio.
1983 Tin Top with a poorly DF and 4 speed DT box.
1987 Electrics and a DJ engine.
Maybe one day I might get it finished

Italjohn
Registered user
Posts: 19
Joined: 03 Jan 2019, 14:31
80-90 Mem No: 0

Re: Blower pwm upgrade

Post by Italjohn »

PWM blower regulator



How I did it:
 

airheadboxer
Registered user
Posts: 52
Joined: 14 Aug 2019, 15:45
80-90 Mem No: 0

Re: Blower pwm upgrade

Post by airheadboxer »

I'm a bit late to the party, but this wiki link may be of interest:

https://club8090.co.uk/wiki/VW_Electric ... ol_Upgrade

AHB
1984 DG Autosleeper

Post Reply