My 05 Octavia heater is blowing the main 40amp fuse each time i switch the heater on, i have replaced the actual blower motor itself, the switch panel in the dash and the speed control resister but have still the same prob.....Any help would be great as its not very fun in these cold mornings as the windows steam up and cant see out.

Does it blow immediately, on any particular setting, or when? I assume that the blower isn't blocked with leaves etc.

Sorry if this is really obvious or if this a common problem on octavias, but here's some ideas:

Unfortunately I don't have a haynes manual for the octavia or a circuit diagram, but if you have access to a multimeter I would probably try something along the lines of the following:

Perhaps try fitting a new fuse and with the ignition off, switch the blower to the highest setting and then turn the key to supply the ancillaries - ?short in switch setting 1 or when switching between 0 and 1.

Remove the fuse and check for continuity btw circuit side of fuse and ground on each speed setting (obviously fan won't work but just each switch setting)

If always shorted:

-> Unplug the cable to the dash control and check for continuity between the circuit side of the fuse and ground, if no short then it's going to be the other side of the switch

If on any particular setting:

-> Check resistance between each wire on the dash fan switch plug and ground, if one is shorted to ground then follow that downstream

-> Unplug plug at resistor pack, see which side of that the short is

If you can't find a short anywhere then is the blower drawing too much current because it's blocked/jammed?

Hope that wasn't too obvious, don't know how much you've worked on car electrics before.

Cheers

Rob

Hey Rob thanks for the reply

Ive replaced all the parts to do with the heater. I replaced the fuse with heater and power supply off then switched it on to number 4 then turned on the ignition the heater was goin perfect but as soon as i switched it back to 3 it blew the fuse, and i tried this for each setting on the switch fron 1 to 4 and it was the same each time. my mate has same car and tried all his parts aswell but no difference.... im takin it has something to do with the wiring but im not sure.

Just to clarify:

Ignition off then on on switch position:

4) Fine until turned

3) Fine until turned

2) Fine until turned

1) Fine until turned

or

4) OK

3, 2 and 1) Blows when ignition switched on?

I think if I get this info I can tell you where to look.

Cheers

Just reread you reply, and I figure it's OK if switched on in any position until changed.

To me, that would point to a fault with the switch, but if you've replaced the dash switch, then it can't be that - is it a simple turn switch or an electronic unit?

I'll have a think and get back to you

EDIT: Also, looking at http://briskoda.net/attachments/25425d1226155131-skoda-fuse-box-diagram.jpg, the fuse is 20A for the blower - is this the fuse that's going? Not that using a higher rating fuse will cause it to fail... If the fuse you're having problems with is one of the 'major' fuses, then I can't be much more help without a circuit diagram I don't think, sorry.

Edited 25 January, 200917 yr by jacko203

Thanks for the help.

Yeh its works fine on any switch position until the switch is moved then it blows the fuse. there is 2 fuses marked for the heater but its fuse number 40 i think and its a 40amp aswell i think it has to be a wiring prob i have..

I can't think of any way that this can be anything other than the switch faulty (shorting to ground somehow on turning), but I don't have a wiring diagram, so it's hard to fully get my head around it. Are there any other circuits running off the same fuse?

Sorry, I'm not sure I can help with this.

Rob

I'd go with the switch as well, sounds like its internally breaking down as the contacts move between the selected speeds.

IIRC, there are two connectors for the heater controls. The fan connector doesn't have a ground, but the other connector does. Try pulling the other connector and see if it still happens.

Try leaving things unplugged such as the fan motor then move the switch. I'm guessing you've tried a new resistor pack for the blower motor?

IIRC, there are two connectors for the heater controls. The fan connector doesn't have a ground, but the other connector does. Try pulling the other connector and see if it still happens.

I've not taken an octavia apart (only driven one as a courtesy car, and not sure they'd like me doing that!), but is it possible to switch the two connectors over when you tried the other switch, blowing the fuse because of that? Probably a different connector, but thought I'd mention it.

On the old golf I fixed, I could take the switch apart, clean it and bend the contacts back into the proper shape; might be worth a try.

Good luck

...is it possible to switch the two connectors over when you tried the other switch, blowing the fuse because of that? ...QUOTE]

No. One is 6-way and the other is 8-way.