Air Conditioner problem.

[GregTD5]

I have a problem with the auto airconditioning on 2001 Discovery.
In auto mode, the air con will only run if I manually set the fan to Max.
Any tips on where to start looking.

Thanks,
Greg

[dirtdodger]

In the D2, the heater/aircon fan speed is controlled from the air temp ecu via a separate power transistor external to the ecu...........

Except when maximum fan speed is selected manually. In this case, the ecu bypasses the power transistor (G109) and energizes a relay (R104) to supply full power to the fan motor.

The first place to start , would be to locate the power transistor G109.
Depending on the model D2, it may be a resistor pack instead of a transistor.
Either way, it is bypassed with max fan speed manually selected.

Remove the glovebox, and mounted to the left on the plastic ducting you should find it........marked G109.
If it is a resistor pack, it has an internal fuse.

It may be the ecu failing to control the power transistor. But, I doubt it. The climate control ecu is quite reliable.
However, a power transistor or a resistor pack that has to modulate current to a fan motor is a likely suspect.


Have fun.

[cucinadio]

In the D2, the heater/aircon fan speed is controlled from the air temp ecu via a separate power transistor external to the ecu...........

Except when maximum fan speed is selected manually. In this case, the ecu bypasses the power transistor (G109) and energizes a relay (R104) to supply full power to the fan motor.

The first place to start , would be to locate the power transistor G109.
Depending on the model D2, it may be a resistor pack instead of a transistor.
Either way, it is bypassed with max fan speed manually selected.

Remove the glovebox, and mounted to the left on the plastic ducting you should find it........marked G109.
If it is a resistor pack, it has an internal fuse.

It may be the ecu failing to control the power transistor. But, I doubt it. The climate control ecu is quite reliable.
However, a power transistor or a resistor pack that has to modulate current to a fan motor is a likely suspect.


Have fun.



bloody hell im glad i own a D1.....:(

cheers

[dirtdodger]

bloody hell im glad i own a D1.....:(

cheers

Yeah.........well............

I did not want the "Thought Police" jumping on me for giving out dud info:angel:

[GregTD5]

Thanks for the info dirtdodger, you couldn't have made it any easier for me. The only problem is, I can't find anything with G109 on it.
I found x2 relays on side of fan motor and what looks to be another 2 ecu's with heaps of wires going in, on left side kick panel.
On right side of fan motor, attached to ducting, I found a Denso unit with cooling fins attached.
I'll go back and have another good look!

Greg

[dirtdodger]

If your vehicle has Nippon Denso climate control. (Indentified by an LCD screen and push buttons. NOT rotary switches), check the unit you have found with Denso on it.

It will have four wires to it,

*Black
*Black with orange trace
*Purple with a green trace
*Green

If all match, you have found it.

[GregTD5]

Yes I have the LCD screen and push button air con.
Those wires all match what I have to this Denso unit.
Looks like a throw away part to me, so of to a wreckers to see if I can find one.
Once again thanks for your help!

Greg

[dirtdodger]

To make it easier for the next poor unfortunate.......

A pic of the power transistor behind the glovebox


http://img223.imageshack.us/img223/6503/d2aircondfancontroloc9.th.jpg (http://img223.imageshack.us/my.php?image=d2aircondfancontroloc9.jpg)http://img223.imageshack.us/images/thpix.gif (http://g.imageshack.us/thpix.php)

[justinc]

OK, I have the need for help here, testing the D2a heater blower speed transistor. The above symptoms are exactly the same, but is there a definate way I can test it without buying one (at a reasonably high price) first:(?

Will a simple continuity test across the transistor help????
Any typical values I should be seeing?

Thanks in aticipation,

JC

[robbotd5]

bloody hell im glad i own a D1.....:(

cheers
Good on ya!!!!
Regards Robbo.

[dirtdodger]

OK, I have the need for help here, testing the D2a heater blower speed transistor. The above symptoms are exactly the same, but is there a definate way I can test it without buying one (at a reasonably high price) first:(?

Will a simple continuity test across the transistor help????
Any typical values I should be seeing?

Thanks in aticipation,

JC

Assuming that you have the Denso system (A lcd screen with push buttons, not rotary switches)
and..... it has a power transistor for fan speed control. (some early, early d2s had a resistor block with fuse)
If your d2 has a resistor block there will be an internal fuse.

O........K.....
The transistor will be marked as "G109" and the connector marked as "C858", hidden behind the glove box.

Four wires to it, on connector C858
* Black, pin 2
* Black /Orange pin 1
* Green pin 3
* Purple/ Green pin 4

Remove unit and test unit with................

A multimeter on low ohms or diode test.

between pin 1 and 3 in one direction should be high resistance, in other direction should be low resistance. (continuity).

between pins 3 and 2 in one direction should be high resistance, in other direction should be low resistance.

Between pins 4 and 1 should be a high resistance both ways.

I have not specified the resistance values because I don't know what transistor type it is, or the collector resistor value.

However..... if you do not get the high/low values where required, its a fair bet that the device has had a meltdown.

If so, pull it apart and check the transistor numbers.
I have a suspicion that it may be a 2N3055 or similar.....common as dirt and cheap too.
You may be able to save a dollar by fitting a new transistor.

Reference: Rave wiring diagram 38:2 and workshop manual 82:12