Motor or switch broken on fan for heater/cooler

workaccount

Hi,
I have an old Nissan driving around at the moment and only the highest fan setting will work. (out of four I think)

It makes it very hard to regulate the temperature.

Is this the motor or could the switch be problematic?

Nissan Sunny btw.

ART6

workaccount wrote: »

Hi,
I have an old Nissan driving around at the moment and only the highest fan setting will work. (out of four I think)

It makes it very hard to regulate the temperature.

Is this the motor or could the switch be problematic?

Nissan Sunny btw.

Fan speeds are generally controlled by a resistor bank, so although I am not a Sunny expert I would have thought it's fan was too. I don't know where the resitor is on a Sunny but they're usually somewhere near the fan casing or in a recess in it. The wires from the switch go to that resistor bank, four of them from a 4 position switch with one earth wire to the car body. Normally three of the wires connect to each of three resistors, while the 4th connects direct to the motor. Therefore, if your fan runs on full speed then the problem might be bad resistor connections, or worn out fan motor brushes. I'd suspect the latter since when that happens there is insufficient power getting to the motor through the resistances to overcome the low brush pressure on the motor commutator. It's a very common fault on older cars.

crosstownk

If only the highest setting is working then it's definitely the series resistance as the highest speed bypasses the resistance altogether to allow full current to the blower motor.

Lucifer

As has been said it is the rheostat that is the problem. Had to replace one on 2 micras and 1 pulsar which should be the same as a sunny, they were located below the glovebox. I think there is a philips screw holding it in and there will be a block connector connecting to it.

will be something like the block connector on the right in this picture but from memory is a little bit more rectangle


is shaped a bit more like this one i think.

workaccount

Lucifer wrote: »

As has been said it is the rheostat that is the problem. Had to replace one on 2 micras and 1 pulsar which should be the same as a sunny, they were located below the glovebox. I think there is a philips screw holding it in and there will be a block connector connecting to it.

will be something like the block connector on the right in this picture but from memory is a little bit more rectangle


is shaped a bit more like this one i think.

Deadly. Wonder why it's under the glovebox?

So it's the black box with the numbers in that first picture is it?

crosstownk

workaccount wrote: »

Deadly. Wonder why it's under the glovebox?

So it's the black box with the numbers in that first picture is it?

It's mounted behind the glovebox because that's where the blower motor is located on most cars and the resistor is usually mounted to the blower motor housing. Once you remove the trim below the glovebox it will be all visible.

workaccount

crosstownk wrote: »

It's mounted behind the glovebox because that's where the blower motor is located on most cars and the resistor is usually mounted to the blower motor housing. Once you remove the trim below the glovebox it will be all visible.

Just found that now in the Haynes manual. I'll get a replacement tomorrow before I take the cover off.

Thanks very much.

E92

Had something similar in my E34 recently. Turned about to be the rheostat wasn't varying resistance, so needed to be replaced. Cost €65 to get it sorted, including labour.