Club 80-90 Forums

CovKid wrote:when I ditch the resistors that set motor speeds and use a motor speed controller

I still reckon a thermocouple in the cab, coupled via a fairly simple circuit connected to an analogue controller for the fan, would give a certain degree of "climate control"

Oldiebut goodie wrote:

CJH wrote:Hmm - I don't understand the discrepancy between those ratings and the Vehicle Wiring Products ratings.

Maximum and SWL.

I figured it would be something like that, but would VW really have used a wire with a safe working load of 8.75A for a blower motor that can draw 10A even when the bearings are fresh? I suppose it's a question of what constitutes 'safe' - a small temperature rise in the wire might be acceptable, especially if it's in a circuit that isn't on all the time. Is it normal to fuse the circuit at the same level as the 'maximum' wire rating? Whatever their reasoning, they seem to have had second thoughts in 1986.

ghost123uk wrote: I still reckon a thermocouple in the cab, coupled via a fairly simple circuit connected to an analogue controller for the fan, would give a certain degree of "climate control"

You design it then, and Covkid can prototype it and put it in the wiki. I moved my resistors out of the heater box when I replaced the motor recently, partly to give me the flexibility to do the controller mod without dismantling the dash again.

Don't forget the servo for the water valve!

All dooable. Will talk with Ghost on thermocouple as we do have each others numbers. Quite a lot of prototyping going on already with other things. I'm a long way into my new rear lights now which are possibly the best ever seen on a T25 - been hacking them over recent years. The Mercdoctors were quite impressed the other night. When switched off, everything looks standard. I still think a proper hatch for blower motor would have made things much simpler in terms of replacement but like many of these areas, VW didn't envisage these vehicles lasting as long as they have, or indeed owners that would want them to.

Putting these in tomorrow

Ah news - motor controller has arrived

Thanks for all the info chaps... looks like its dash out what's the best guide and any tips, have seen wiki but there's always new ideas.( cant really be bothered ) at this time..

https://www.youtube.com/results?search_ ... sh+removal" onclick="window.open(this.href);return false;

Where does the heater fan actually pull air from exactly?

ScienceBoy wrote:Where does the heater fan actually pull air from exactly?

Through the grill above the radiator.

Which is fine in Summer but not so hot (excuse the pun) in Winter if the flaps don't fully close. I tend to rely on the Propex for at least the first three miles. I keep meaning to run a Y-piece from Propex that would couple to dash outlets. In the Summer, the best source of cool air is opening quarterlights.

Just watching this so I can read it atr work later, thanks.

If you replace motor, it pays to fit one of these too:

https://www.youtube.com/watch?v=3GzJ8N1Rqp8" onclick="window.open(this.href);return false;

Although the stock resistors work as a way to get lower fan speeds, its a very inefficient way to do it.

The original return (earth wire) on motor goes to minus connection on controller instead of earth crown.

Covkid,

I bought one of these, took the old switch out and found that I had two yellow wires and one white one coming from the fan, and a black Red wire coming from my ignition live feed.
I tried as many combinations as I could but I could not find the one where the fan would turn!
Do you have any idea what the different colours are for?

It depends how your new fan was packaged when you got it but you only need two wires from fan which should BOTH go to controller ONLY. The earth (negative) must go to controller negative. The positive at fan should go to positive at controller. On a stock system the only wire on blower switch that actually matters here is the yellow one - this is the flat-out speed and ignores the resistors.

Heres how the stock system works so you can understand what needs to be done:

Firstly, go grab your Haynes manual and turn to 12.38 - (wiring diagrams) - its towards the back.
See V2 bottom left? thats your blower motor.

The wire below it is the earth (brown) trhats going to earth crown. Just above the motor there are two other wires that connect to it, but further up there are three that come out of E9 (the fresh air/heater blower switch) - the three wires for the three different speeds. By default the motor runs full pelt so they added Dr Frankenstein resistors (N23) to slow it down for the two other speeds.

Basically these are the three speeds and the wires are coloured thus:
1) ge (stands for yellow and motor would be flat out)
2) ge/sw (yellow and black - motor at medium speed)- power now going through one resistor
3) ws (white - motor at slowest speed) - power now going through TWO resistors

So, the only wire you need (if you leave resistors where they are, is the solid yellow (flat-out) one. Thats positive and should go to motor-positive on controller. Ignore yellow/black.

The brown that normally goes left, under the dash to earth crown needs moving and should now go to motor-negative on controller. The other terminals (plus % minus) on controller are for your 12v feed. The one you found from ignition should go to battery-positive on controller and the negative you can just ground to chassis. My video helps you translate chinese symbols. If your new fan has extra wires, you can ignore them.

If you;re still stuck and have some photos I can guide you no prob.

Subnote:

For anyone else fitting this mod, DO NOT fit it to an old fan motor. Only do this with a new one. Old motors draw considerable amps at startup which might damage the controller. Therefore this mod needs new fan, new controller - period. If you've not long fitted a new fan and want to go PWM, you can do it with dah in situ but you have to discover which brown wire at earth crown serves the blower and the only sure way to find out is turn on blower and disconnect earths one at a time until blower stops - you've found the right wire. As mentioned above, that wire should go to motor-negative connection on controller instead. If you don't do that, controller will have no effect on blower speed at all. The controller MUST have the blower to itself - if that makes sense.

Many thanks.