Interior blower/fan only working on slow speed.....ideas?

Anyone come across this problem? The interior fan only works on the slow speed! It does switch off when the 'OFF' button is pressed and comes back on when the fan speed knob is turned but only the slow speed (1st speed). We have fitted a NEW fan speed controller loacated near the fan motor just behind the lower glove box, passenger side footwell, no effect. We have exchanged the dash switch cluster/panel with a working one from my Supra, no effect. We have swapped the relay in the fuse box marked HTR, no effect. The air con works ok, all flaps seem to work ok when the AUTO climate control is engaged, the heated rear window works ok, the heater gets hot and warm/cold air comes out of the vents, all the switches and lights in the switch panel/cluster work ok. Car has not been messed about with the only thing fitted which is non-standard is an Alpine stereo CD unit.

Any pointers/help would be much appreciated.

has anyone any ideas on this as this is a problem i have with my car?? any help would be great

Andy

bump this up as this is just like my problem exept my rear window heater dont work either!! cheers

Andy

do the supras have a resistor? if so that could be the problem. not sure the heating contorols take power form the stereo iso harness though

if it has a resistor then High speed feeds straight +12V to the motor, but the lower speeds drop the motor voltage through the resistor. The lower speeds usually fail first, because that's when the resistor gets hottest and doesn't get cooled because the air is also moving over it the slowest but as i say im unsure the mk4 has a resistor.

cheers mate, i was out having a look about it today and i think they do have a resister under the blower fan in a small case, everythin looked ok though, will need to get someone to test it somehow see if it is the resister or evan the blower!! will be a case off trying each part off the heating contols too see witch is faulty! cheers

Andy

cheers mate, i was out having a look about it today and i think they do have a resister under the blower fan in a small case, everythin looked ok though, will need to get someone to test it somehow see if it is the resister or evan the blower!! will be a case off trying each part off the heating contols too see witch is faulty! cheers

 

Andy

resistors are hard to test, best bet is try a spare from someone, but usualy on moast cars when there is only 1 or 2 fan speeds working then it ends up being this. the fan motor will only be an on/off (should be) and the resistor is what controlls the speed signal to it. try a new resistor first, someone here may have one

cheers for your help buddy :)

Andy

Might be worth just buying a new heater control box could be something internally in there. I have a heater box that did that but it happened after i tried the blue led conversion never tested the box to see if it was like that before i did the conversion. So i bought another one and that works perfect. Can pick them up for around £30