Blower switch nightmare

[Reimotim]

A while back my blower switch stopped functioning properly and required a little wiggling to get the fan to go. Then I lost speed 1, but still had 2 and 3 if wiggled into place gently. "Oh well" I thought, "nothing too complicated, I'll order a new switch..."
New switch arrived from Jk, Christmas came and went, then I thought about doing that "5min job".

I duelly disconnected the old switch, fitted the new one and the inserted the control knob into the switch and pushed it firmly home ... Suddenly the back of the switch popped off, depositing the inner workings all over the inside of the dash.

Back on the phone to JK and they very kindly sent a replacement. Which I have fitted today. All good... Except it doesn't seem to work consistently. The switch still needs wiggling to get the motor to run and if I take my hand off the switch the motor stops.

I thought that there must be a problem with the connector block, but upon closer inspection that is fine and it seems down to the switch.

Am I missing something, is it possible I,ve been sent two dud switches? I thought about getting one from VW heritage, but they stock the switch from the same supplier.

I put a multimeter on to test that the switch was making a circuit and it does seem pretty hit and miss and seems to rely on careful positioning of the knob .

Help! I want a functioning blower.

Is this really down to cheap and faulty parts or is there something else, I'm overlooking.

Thanks in advance

Tim

[CovKid]

I would have thought any rotary position switch would do providing it can handle the amps.

Have a nose: http://www.ebay.co.uk/sch/i.html?_from= ... h&_sacat=0" onclick="window.open(this.href);return false;

You just cut down the stem to suit your needs.

[Reimotim]

Thanks CovKid

[CovKid]

Just watch shaft size to make sure your knob fits (oooer) but otherwise a four position one will do. Doesn't matter too much if there are more positions I suppose - you just don't use them. Ghost123UK may be able to pick out a suitable one for you - more his thing. I'm not sure of the potential amps through the switch.

[Hacksawbob]

I had a look at this a while back
https://club8090.co.uk/forum/viewtopic.p ... r&start=15" onclick="window.open(this.href);return false;
and tried a PWM resistor running through the high speed wiring, it didn't last long though and got really hot!

A replacement switch needs to handle at least 15 amps, preferably 20A, I had to grab one of these from halfords to keep me going:( http://www.halfords.com/motoring/garage ... tch-hef422" onclick="window.open(this.href);return false;

[California Dreamin]

You also need to consider that there might be other underlying issues. Typically, fan switch issues are a product of high current load caused by a failing blower fan....are you hearing any high pitch squeezing noises?

Martin

[CovKid]

And the olther one - the blower relay. Bad connections on that can cause wires to heat up and the fuse to blow - just as much as fan itself. I was convinced my fan was the cause until I reseated relay.

[California Dreamin]

Relay? do you know something I don't..again? lol

Martin

[CovKid]

Not sure about later/other models Martin but certainly mine definately does use a relay for full speed. Its tucked up above the earth crowns and its evidently been there since it was built.

Last year I was having to increase the fuse rating (slightly) for the motor to keep it going, concluding (as we all do) that the motor was on the way out. However, the motor operated smoothly, so when I had the dash out, I followed the circuit more carefully and discovered that the flat-out position on the blower has a relay in the circuit. The fuse only ever blew in flat-out (non resistor) mode. When I unseated this relay, the terminals were corroded and there was evidence the wires to it had been heating up. With a good clean and dash replaced, I was able to fit the correct fuse and the problem went away.

From a technical point of view this would make a lot of sense since if you went from say zero to high speed, the initial draw is substantial. Whether this continued, or is in all or just some T25s I cannot say but its possible this fault didn't crop up when you worked for VW (they were relatively young vehicles then) but has in more recent years. I've seen three vans like that, including my own. I have to say, its not easy to see or get at, but its up there. It would seem incredulous that Vw would rely on that tiny blower switch to shunt the load. or did they just fit a meatier switch post-85?

I think Fazzer also recently encountered this.

[Reimotim]

You also need to consider that there might be other underlying issues. Typically, fan switch issues are a product of high current load caused by a failing blower fan....are you hearing any high pitch squeezing noises?

Martin

Hi Martin,

I'm fairly sure the motor is ok. I replaced it about 18months ago. It runs smoothly and doesn't squeak.

I haven,t tried simply connecting the terminals and seeing if I get a consistent run then. May be that is the next step.


Tim

[ghost123uk]

Neither of the 3 post 85 vans I have had had a heater fan relay, must be a "MKI" thing.

Agreed with the partially seized fan pulling large current theory as mentioned above. It's all too common. I have had to do it twice (on different vans). You could measure the current at full speed to compare with a known good fan motor (which pulls....... Oh heck, I don't know )

The other possibility, especially after the way your first switch fell to bits, is JK's legendary parts "quality"

I would "hot wire" it without the switch (so it will then be on full speed) and measure the current flowing (if you have a meter with a 10 amp current range). I can measure what my new motor takes and that will either point to a failing motor, or not.

[Oldiebut goodie]

That is the rad fan relay up there above the earths - that's the one that I had to ask what it was for a few years back, did have a pic but can't find it now. Has a big fuse, 30A or 40A or 50A on it.Nothing like being sure as to the rating!

[CovKid]

Rad fan relay sits alongside it. I suppose its possible someone retro-fitted it but looks like its been there from the start. I'm on the 'cusp' year so perhaps it only appeared in the 84/85 when one design came to a halt and everthing changed. VW did some weird things in the gap between the end of the Aircooled models and the 86-on models. Notably the blower was piggy-backed from the wiper circuit so that may have been 'a solution' at the time?

[Oldiebut goodie]

If I remember correctly there were some more original mounting holes near that on mine so maybe you are correct.

[CovKid]

You wonder though, why they didn't split blower from wiper fuse at same time or even 'instead of'. It could be that this sharing of fuses was identified as a problem during production over those years, hence that solution. Seems a bit half-cocked though. Anyway, I finished the job, left the relay as wired and split the fuses. Not had a problem with the fan since. Same with rad fan relay - that was corroded up too - clean sorted it.