Blower fan acting crazy - solved

[Sol]

Hi all, well it's happening to me...the dreaded heater blower acting up. I'm on hols in a week so will have the chance to fix it if it lasts another week. I know where the blower is, how to get it out, where the fan resistor is and where the relay is.

My tale is a bit different to the usual issues though.

A week ago, the fan started making a chirpy sound, kind of jangly chirpy cricket noise, at speeds 1 and 2. It sounded fine on speeds 3 and 4. A few days later it started chirping and jangling in speed 3....only sounded fine on 4.

Then it began to cut out, after a while it would start up again....but behaves like a variable pitch fan....speeds up, slows down....blows fine...then jangles and slows down. 

When the heat setting is turned to exactly the last black notch before full temp, it whistles sharply like a jet engine. Below that, it runs at varying speeds and sometimes stops altogether, then runs again. 

So...I have manual AC and can't decide which motor I need if the motor is bad but as I'm a controls engineer I will pull the motor and service the comm and brushes as a starter for 10. Some have a black impeller, some have a white one. I think I need the white one but will know when I pull it out.

Thoughts are, the control panel is bad, or the transistor pack on the motor if it has one.

Anyone had this behaviour and share any insights before I pull it all out?

EDIT - If you want to jump to the removal process for the fan and resistor - click here: https://www.berlingoforum.com/thread-201...#pid127842

[Gryffindor]

First, I know nowt specifically, so forgive me if this is not helpful.

As a kid (10-12 yrs?) living in an unheated house, I went through a phase of rescuing old fan heaters and trying to fix them (didn't last long!). Most of the time, the problem was that the plastic fan blades were push-fitted onto smooth metal motor spindles, and the plastic hubs had got so worn over time that they slipped when the motor was started up. That slipping mate a squeaky-screechy noise, intermittent or constant depending on how bad the wear was.

If the fan was wobbling on the spindle, then the sound that made could be called chirpy etc. It would happen each time the plastic fan made brief contact with the spindle and got spun up for a tiny moment. Bit like a bouncing violin bow maybe?

Because your sound has begun relatively quickly, it may be that your fan blade's hub has split. And because the noise soon changed characteristics, perhaps the split did too?

Just a guess of course. A quick temp fix if I am right might be a cable tie or jubilee clip if the split isn't extensive, but either would affect the centre of centrifugal force so would not be good in the long term.

Something I've been trained to do in trucks (though not by my current employer) is to always open one window in the cab just a tiny bit whenever putting the fan on full speed, so that the wind it generates has somewhere to escape, thus putting a lot less strain on the fan and making it live longer. The change in its tone as you open a window is quite apparent.

[Sol]

All good points there mate. I can pull the fan motor and service the brushes and commutator, hoping the onboard speed controller is not fubarred and take it from there. What's odd is the heat setting seems to affect the fan speed directly so it may be the dash panel control is faulty, but that wouldn't cause the chattering sound. Unless I have more than one fault....

And the usually handy catcar shows 3 part numbers for the fan model related to my VIN, but 2 say "automatic air conditioning" and one says "no air conditioning" yet I have manual air con, with an AC switch and rotary controls.

It must be a printing mistake but I can't identify which of the two AC models will be mine and with a new fan motor in the eye watering price range it's a costly mistake to just choose one. eBay sellers will say anything so that's no guide.

I can just pull it and if fooked, look for a new one from the sticker part number but then it's (the van) not useable till I get a replacement.

Currently the part of Scotland I live in is at low single figures and pissing down most days so a fan is a must have. I was hoping someone would say oh mine is the same manual AC and I had to get a 6441 GR or whatever, that would give me a head start.

Again the speed control resistor and thermal fuse may be acting up and causing the stalling and weird speed behaviour but not the chattering at low speeds.

If I only had one symptom it would be easy to solve, not 3 lol.

[ffrenchie]

What's odd is the heat setting seems to affect the fan speed directly

The heat setting just operates flaps to allow cold air to mix with the hot so it can't affect the electrical function of the motor speed. It does change the air resistance to the fan making it sound different.

[jj9]

As far as I'm aware the fan has no built in speed controller, the speeds are controlled by the resistor pack which works in conjunction with the blower switch to reduce the voltage to the fan to give the different speeds.

Heater fans normally use Oilite type self lubricating bearings which can dry out over time and start to seize on the shaft which can cause strange sounds & behaviour.

Hopefully your problem is nothing more than this, or worn brushes.

.

[Pedronicus]

No experience with vehicle fans but with my knowledge of large building aircon/vent systems I would suggest either one of the bearings on the motor has failed or the impeller has come loose on the shaft. Maybe even some debris in the fan scroll.

[Sol]

Yeah all possible outcomes. I'll find out this weekend when I pull it out.

First 15 mins it sounds perfect and works like normal, then it starts to chatter, then the speeds get wonky. Changing the temp to a higher setting makes it start a high pitched whistle like a turbo spooling, which instantly stops when the temp control is turned back to mid way.

Bad bearings usually sound worse at higher speeds, this gets better at 3 and 4 when it starts, then after a while 3 is clattery and only 4 is smooth. Then it cuts out after that and next morning, fine again.

[Gryffindor]

If it's okay for the first 15 mins then isn't, that might suggest some component failing when it gets warm? Could be either an electronic or a mechanical component of course. If the impeller is plastic and rubbing on the motor spindle, then it could be friction warming its hub up and softening it.

That might suggest that you'd need to investigate it when it's warmed up - symptoms might not be so evident when it's cold?

The noise may not just be speed-dependent or temp-dependent; it could also be dependent on resonant frequency for example.

Okay, we all know cheap eBay gadgets are rarely what they claim to be, but just to keep you warm(ish) for a week while you do this surgery, how about one (or two) of these?

https://www.ebay.co.uk/itm/312870623880

Don't go flattening your batt though!

There are of course many other models, and cheaper, from China, but I limited the '12v ceramic heater' results to the UK because of your urgency, and as a result only this one caught my eye as having any sort of promise.

Of course you could easily put it back on eBay later.

If you are willing to wait for stuff to come from China, then this sort of thing might be more viable:

https://www.ebay.co.uk/itm/254729281113

Not too sure what the central heating pipes are for though.

Re your Catcar woes and eBay trader despondency, wouldn't one of the reputable parts suppliers' websites be able to specify the right unit with your reg etc? With luck it'll tell you the part number, then you can go back to eBay for a pulled one.

Lastly, just a thought: would the fan be connected up to the canbus, and if so, would the ECU do things to it if it detected a fault, and cease if the fault disappeared? That might be one of the contributory factors to your complex symptoms...

[Gryffindor]

Sorry - just noticed. That ebay heater says 12v in one place and 240v in another... the pics suggest it is not for use in a car. Oh well.

[Gryffindor]

https://www.ebay.co.uk/itm/164219697237