s2 climate problem

[Sindres2NORWAY]

Have a big big problem with the aircon on my 1991 s2.

the heater fan will not at any stage blow air out.
when i measure the plugs i have +12volt. but when i connect the fan the voltage goes to +0Volt.

i have tested the fan with a battery 12volt source and the fan works great.
All of the flaps and heat regulation works so its just the fan that will not blow any air

its the early aircon controller with LO HI controll of the fan.

any tips of what the problem can be ?

thanks from norway

[Sindres2NORWAY]

now i suddently have +6v. any guesses ?

[johne]

Your fan motor speed is controlled by the Blower Control Unit which sits just to the left of the fan motor on the side of the housing. I'd check first that the two connectors to it are good.

There's 4 wires going to that unit:

Black/Blue going to pin 2/B which brings in the 12 volt supply via fuse S17 which is also the fuse for the Climate control unit.

Black/White going to pin 1/B which is the speed control signal from the Climate control unit pin 15

Black/Red going to pin 1/A which is the +ve supply to the fan motor and also goes back to pin 14 on the Climate control unit so it can monitor the fan speed setting

Brown going to pin 1/C which is the ground/earth.

If the voltage on pin 1/A never rises above zero then the fan motor won't run. If there's 12 volts on pin 2/B and a control signal on pin 1/B that changes as you change the Hi - Lo on the Climate control unit but the fan motor still won't run I'd suspect the Blower control unit.

Does the fan run when you select "Auto" mode?

Hope that helps, information all taken from Bentley.

John

[Sindres2NORWAY]

Thanks for quick answer johne

The fan will not work at any setting or speed.

Im going to measure tonight but is there any way to bypass the blower control unit?

and does the heater fan go thru a relay ?

[johne]

Thanks for quick answer johne

The fan will not work at any setting or speed.

Im going to measure tonight but is there any way to bypass the blower control unit?

and does the heater fan go thru a relay ?

It does look as though your Blower control unit is faulty, but also there could be no control sugnal to it from the A/C Control Head. You could bypass it by linking the Black/Blue and Black/Red wires at the Blower control unit connector but then your fan would run at full speed all the time. Would be a good check to see that everything else works though.

There is no specific relay for the fan motor, power is supplied - as well as to lots of other things - by the "X" relay, the load shedding one, in position 5 in the main fuse box.

John

[Sindres2NORWAY]

Black/ blue wire has +12v direct from fuse 17.

Black/White going to pin 1/B has +9,49 on lo setting, and +9,52 on hi setting

Black/Red going to pin 1/A has +0,65v

if i take a wire from black/blue -> Black/red the fan blows like crazy!

so it seems like i have control signal on black/white
and +12v on black/blue.
black/red have 0.6 V

have testet with another AC display unit,and have the same measurments

So im wondering, the 0.6 volt i have on black/red Pin 14,is it the correct voltage from ac display unit ?

Sindre

[johne]

So all your wiring to the fan and Blower control unit is working.

I don't know what form the signal on the Black/white wire from the A/C control head takes but I'd expect it to be a pulse waveform with varying mark/space ratio hence you seeing an almost constant 9 volts. You'll need an oscilloscope or another known good A/C Blower control unit to check it out.

As all your wiring is good and you've got some sort of signal from the A/C Control head, it looks more and more likely that your A/C Blower control unit is blown which isn't surprising given the high current to the fan motor it has to cope with.

John

[johne]

Just seen your edited post.

The 0.6V on the Black/Red wire to pin 14 on the A/C control unit isn't a voltage out of the the A/C control unit, it's the voltage that the A/C Blower control unit is feeding back to the A/C control unit so the A/C control unit knows that the signal it has sent to the Blower control unit on pin 15 is being worked on correctly by the Blower control unit - which in your case it isn't!

If things were working normally you'd see from zero to 11 volts on pin 14 as the fan speed increases.

Time for a new or replacement Blower control unit..........................

John

[Sindres2NORWAY]

The wiring seems to be correct yes.
i think theres time for a new blower control unit hehe
thanks for the good help johne