639 Vito heater fan problem. Going nuts!

[Steve Jowett]

Hi all, Hoping someone can shed some light on a problem. The heater fan suddenly stopped working in my 2004 Vito (no A/C). Thought it was the usual so bought a new resistor pack. Still nothing. Changed the heater controls for a supposedly known good pack. Still nowt.
Put old resistor pack back in. In fact tried all combinations. Got the multimeter on the connectors. 12v to the switch, nothing out on any speeds. Bridge the contacts on the connector and get all 5 speeds!
Took the switch pack apart and there's a tiny 'fuse' strip on the fan switch connections which had melted on both switch packs. Can only assume it's a fail-safe in addition to the actual 40A fuse. Worked out it is a 30A maximum draw on the blower motor so soldered a 30A fuse wire to bridge it. Re-assembled and it all works!
Only trouble is, it is now permanently live, i.e. the fan works even with the ignition off, the key out and the van locked. So I have to remember to switch the fan off to '0' before I leave the van.
It's driving me mad! The Merc wiring diagram doesn't make sense to me either.
Does anyone have an idea? Please. Or I may take my Kango to it!
TIA

 

[Kev555]

Good fix Steve but sorry dont know why its always live after what you described as a solder fix. Any solder dropped onto contacts or board below it by any chance?

 

[Steve Jowett]

Good fix Steve but sorry dont know why its always live after what you described as a solder fix. Any solder dropped onto contacts or board below it by any chance?

Hi Kev,
No, fairly tidy soldering job on both switch packs and both do the same. There’s nothing behind that circuit board either. Not sure if the SAM system has any input in the circuit. Weird. Thanks for the reply though!

 

[Steve Jowett]

Just stopped. Fan blower works fine, no noise. Nothing blocking it.

 

[baddesley5]

I know this is an old post, but for anyone with this problem I can shed some light on this. I've just fixed the same problem on an 08 Vito 639 for a friend. The fan speeds gradually stopped working, but it still worked on full speed. Then that stopped. I bought a new resistor pack for it, assuming that would be the problem. However, replacing this made no difference - still no blower/fan.

I found this post and took the control panel out. Yes, it looks like there is a fusible link between the control contacts, but this is NOT a link. These are simply metal ‘fingers’ that hold each contact to the plastic base! The ones shown just happen to be close together to look like a blown link. If you connect these two together, you will have shorted out the power to the first contact (low speed), so it WILL run permanently!

If the resistor pack doesn't fix it, you have another fault. In my case, it was the fan motor brushes. One was worn out and not contacting. A new motor from eBay for £38 fixed it! If you have a meter or test bulb, see if you have power to the centre fan connector. If you have power, your fan is faulty. If not, check fuses etc. Don't be tempted to try changing the brushes or buy a used motor, it's not worth the trouble.

To remove the power connector to the motor, use long nosed pliers. Remove the one to the resistor pack by pulling out the pack first, it's easier. Push the cables to the far right, over the edge of the cover to enable you to pull the cover out (remove the three torx screws first), so you don’t have to remove the connector right at the back (break a small plastic clip right at the front to enable the cable to pass it).

However, DON'T remove the heating control panel unless you HAVE TO - it’s a pain to put back. There are two linked rods and shafts on the top controls that are basically impossible to get back without removing the lower panels. The rods and shafts only go in one way round, so you can’t get them in wrong.

It’s unlikely, but the problem could be your control panel, as the contacts get dirty and greasy. If you don’t have power to the fan, look at this as a last resort: clean it with WD40 and a cloth.
P.S. I am an Electronics Engineer.

 

[MinionBob]

Thanks for taking the time to post that, always very useful those kind of snippets of wisdom.