Heater only working on 4 !

Hi all,
I have a 97 300Tdi non air con and all of a sudden the heater will only work on the 4th setting. There are no overheating issues (that I know of) and have no idea where to start! I guess its not a fuse as 4 works... Any ideas??

Thanks

Right its the heater resistor pack

Quite a common fault on a lot of cars, it will probably be the resistor pack has gone.

BLOWER CONTROLS K1
CIRCUIT OPERATION 1
CIRCUIT OPERATION
Front Blower
With the Ignition Switch (X134) in position II, battery
voltage is applied to the Ignition Load Relay (K127).
The relay is energised, applying battery voltage to
the Front Blower Motor Relay (K192).
When the Front Fan Speed Switch (X247) is turned
to position I, ground is applied to terminal 85 of the
Front Blower Motor Relay (K192). The relay is
energised, applying battery voltage to terminal 2 of
the Front Blower Motor (M101). Ground is applied to
the Front Blower Motor (M101) through all three
resistors of the Front Blower Resistor Unit (Z214).
The Front Blower Motor (M101) then runs at low
speed. When the Front Fan Speed Switch (X247) is
turned to position II, the Front Blower Motor Relay
(K192) remains energised. Battery voltage is still
applied to terminal 2 of the Front Blower Motor
(M101). Ground is now applied to the Front Blower
Motor (M101) through two resistors of the Front
Blower Resistor Unit (Z214) and the Front Fan
Speed Switch (X247). The motor then runs at the
low–medium speed. When the Front Fan Speed
Switch (X247) is turned to position III, the Front
Blower Motor Relay (K192) remains energised.
Ground is now applied to the Front Blower Motor
(M101) through one resistor of the Front Blower
Resistor Unit (Z214) and the Front Fan Speed
Switch (X247). The motor then runs at the
medium–high speed. When the Front Fan Speed
Switch (X247) is turned to position IV, the Front
Blower Motor Relay (K192) remains energised.
Ground is now applied directly to the Front Blower
Motor (M101) through the Front Fan Speed Switch
(X247). The motor then runs at high speed.
Fresh Air Mode
With the Ignition Switch (X134) in position II, battery
voltage is applied to the Ignition Load Relay (K127).
The relay is energised, applying battery voltage to
the Air Recirculation Solenoid In–Line Fuse (P138)
and Air Recirculation Solenoid (K123). When the Air
Supply Selector Switch is moved to the Fresh Air
position, ground is applied to the Air Recirculation
Solenoid (K123). The solenoid now opens the fresh
air intake flap allowing fresh air to enter the vehicle
cabin. When the fresh air intake flap has been fully
opened, the microswitch inside the Air Recirculation
Solenoid (K123) moves to the Fresh Air position
interrupting the ground supply. The solenoid now
stops and remains in the Fresh Air position.
Recirculated Air Mode
With the Ignition Switch (X134) in position II, battery
voltage is applied to the Ignition Load Relay (K127).
The relay is energised, applying battery voltage to
the Air Recirculation Solenoid In–Line Fuse (P138)
and Air Recirculation Solenoid (K123). When the Air
Supply Selector Switch is moved to Recirculate Air
position, ground is applied to the Air Recirculation
Solenoid (K123). The solenoid now closes the fresh
air intake flap allowing only the air inside the vehicle
cabin to circulate. When the fresh air intake flap has
been fully closed, the microswitch inside the Air
Recirculation Solenoid (K123) moves to the
Recirculate Air position interrupting the ground
supply. The solenoid now stops and remains in the
Recirculate Air position.

Hope_5 said:

Hi all,
I have a 97 300Tdi non air con and all of a sudden the heater will only work on the 4th setting. There are no overheating issues (that I know of) and have no idea where to start! I guess its not a fuse as 4 works... Any ideas??

Thanks

Click to expand...

It's the resistor pack that's gone and it defaults to #4 Very easy job to replace.

Remove the glovebox and you get direct access to the fan itself and the resistor pack is attached to the fan housing. 30mins tops to do.


Dave

Thanks for the replies. I was worried it was a dash out job! Am I right in thinking this is the part I need?

LANDROVER DISCOVERY 1 - 300TDI - BLOWER MOTOR RESISTOR | eBay

That's the one. Really easy job, via the glovebox area.

Thank you!!