Heater blower not working

[Dano41]

Hi,I have a 406 diesel saloon 1999 the heater blower is not working.Read other threads on the net and on here a lot of them are out of date or the pictures are no longer accessible or seem to be different from mine.I have checked the blower with another battery connected to the red and black wires which you can see in pic and it is working.Is there anybody here with the same set up as mine who has bypassed the ignition switch with a relay and can tell me how to do it please?A lot of posts talk about a 40 amp fuse in the drivers side fuse box with a heavy red wire going to it,dosen't appear to be in mine.With engine running there is no power going to the black and red wire passanger side which are connected to the green and grey wire.Which of the fuses on my board are for the blower,which of the wires coming from the ignition barrel is the one for the blower?Any help would be greatly appreciated.Dan

[flyin2wheeler]

Im having the same issue on my 04 hdi but your fuse boxes are both different from mine.
I havent got really indepth to testing mine but I do know,theres no power headed to my fan.
My plan is,live feed from the battery to a relay and using the radios live wire to activate the relay and make the fan work

[flyin2wheeler]

Did a few tests on mine tonight,very odd!!!
Full power going through all the red wires to the fan,no issues there.
Black wire to the fan,did a continuity test to an earth point on the body...nothing!
took fan out,going grand with a 12 volt feed to it but,my earth aint earthing!!!!
Did a temp repair,black wire on fan,joined in a section of cable and earthed to the body but fans running flat out as soon as i fire up the car.
im thinking its my controls are dickie!

[steve_earwig]

Sedre is unclear what actually controls the fans, but from your findings I guess it's the earth that varies (pwm?).

It also seems to say the control box can be part of the fan or it could be separate:

D9FM blower cotrol module.JPG

(62.58 KiB) Downloaded 1 time

[GingerMagic]

Hi, I would suggest the resistor as first port of call, when they fail you are left with a fan that won't work, or a fan constantly on full speed...
I don't know if it's the earth that is resisted, to set the speeds - I'm crap with electrics - but a wiggle of the wires going to the resistor, when the engine is running, may help?
Also, sometimes the ignition barrel leads can fail - easy to replace.

Apologies if you have already read all this on older threads...

[flyin2wheeler]

sorry to hi jack this thread,earth going into my resistor,no earth going to the blower
Took it apart and it has a field transistor inside which id say is the culprit

[PeterN]

There is usually a separate thin lead from the control panel which varies the voltage on one of the transistors on the motor control circuit, it only varies the voltage by a very small amount, probably less than half a volt, if you disconnect this lead it shouldn't work, if it does the transistors have failed - this is all assuming that the car has climate control.

Peter

[flyin2wheeler]

If I knew what type of FET it is thats screwed to the heatsink it would be a handy fix as those field electronic transistors are only about £1.50 from CPC

[steve_earwig]

The transistor's been mentioed a few times e.g. viewtopic.php?f=3&t=13315&hilit=transistor but I'm not sure if there's just one or (as seems more likely) lots..

[PeterN]

I am only familiar with the XM heater which I think is similar but probably not exactly the same. that uses a pair of MJ11015 which are actually Darlington pairs, although I didn't know that and fitted a pair of ordinary bi polar transistors which worked fine, possibly any heavy TO3 PNP type will work?

Peter