Is your Fiat Ducato / Doblo
Heater Resistor faulty?

The problem

Since 2005, many Fiat owners have experienced a problem with the heater fan not working properly.
Vehicles affected include the Ducato and Doblo II.

Two types of controls are used, depending on whether the vehicle has climate control / auto air-con or not.
Generally, it is the vehicles without digital auto air-con that have the most common problems with the heater and this is the vehicle we are dealing with here.

Owners may experience an intermittent heater blower fan, on one or more of the speed settings, or the fan may not work all, or will only work on full power, or may be stuck on full power.

The possible causes

There are two common causes of a heater blower fan problem in the Ducato and Doblo without auto aircon:

A. Faulty Heater Resistor (Otherwise known as the Heater Blower Resistor, Resistor Pack, Heater Rheostat or Blower Motor Resistor, (Part No: 55702407 13248240 77364061 6436C4)
Usually, it is the thermal fuse on it that fails.

An open circuit Heater Resistor Thermal Fuse 

B. Overheated/Burned Heater Resistor Wiring Loom Connector
The connector can become overheated and melt, causing damage to the loom.

An overheated/burned Heater Resistor Loom Connector

The fixes

A. Faulty Heater Resistor
If it is the thermal fuse that has failed, you can just replace that, using our thermal fuse repair kit.
Find out more replacing a thermal fuse
Alternatively, replace the Heater Blower Resistor with new.

B. Overheated/Burned Heater Resistor Loom Connector.
Replace the wiring loom connector by fitting a Repair Loom.
(Part No: 55702409)

C. Other Causes
There can, of course be other causes, like a faulty blower motor, or a blown fuse, but the two main causes above are far and away the most common.

Repair guide
Stage 1 - Investigate.

If your heater blower is totally dead, do check your fuses first.

Disconnect the Heater Blower Resistor from the loom for inspection.
The Thermal Fuse is shown arrowed here.
It should read short circuit (zero ohms)
This is the usual cause of failure of the Resistor Pack.
You can fix this with our Thermal Fuse Repair Kit.



Now carefully inspect the Heater Resistor Loom Connector.
Here's an example of a badly overheated one.
Clearly, this one needs replacing, but even if yours looks OK, look carefully at the contacts, and replace the connector if at all doubtful, using our loom repair kit.

Repair guide
Stage 2 -
Order new parts as appropriate.

Repair guide
Stage 3 - Replace/repair.

Replacing the Heater Resistor Thermal Fuse

1.Cut off the old fuse, leaving as much lead length remaining as possible.
2.Use your pliers to straighten these legs.

3.Bend the legs of your new thermal fuse into a "U" shape.
4.Now crimp the new fuse onto the old legs, such that the fuse is still close to the Resistor Pack body.
Cut off the protruding legs, and the Heater Resistor is repaired and ready for re-use.

Don't forget to try and determine why the fuse failed in the first place.

Replacing the Heater Resistor Loom Connector:
To do this, you need to cut off the old connector, and connect the cables on the new loom kit to the original loom.
For safety, disconnect the battery first and make a note of the radio code.

Eliminate the possibility of making a wiring mistake by cutting, and crimping or soldering only one cable at a time.