The problem

In the headlines now, following reports in the media of numerous fires in Vauxhall and Opel Zafira B vehicles.
The fires are especially disturbing because they start suddenly, inside the vehicle, without warning, and the driver often has the added task of unbuckling possibly 2 or 3 young children from their safety harnesses in order to make an escape before the fire envelopes the interior.
There has also been at least once instance of the driver being trapped inside, unable to operate the electric locks.
Fortunately, to date, nobody has been seriously injured, but the risk for potential tragedy is obvious.
The fires start in an area behind the dashboard and are reportedly associated with the heater blower resistor.
Vauxhall have issued a statement and are recalling all vehicles potentially affected.
Vauxhall statement on Zafira fires
They state that it is only vehicles WITHOUT automatic aircon (ie climate control) that may be affected, and not Zafira A's, or the current Zafira Tourer.
They point blame at the incompetent repairs and/or the fitting of non-approved parts by independent garages.
However, BBC's "Watchdog" has cited examples where the work has been carried out by Vauxhall - and of course they will only use genuine Vauxhall parts.
There have also been reports of fires in vehicles not long after having been declared safe following a recall inspection.

The cause?

The heater blower resistor (otherwise known as the resistor pack), is being blamed as the cause.
But why on this model only? Or are other models likely to be affected too?
So, lets take a look at the heater blower resistor from a Zafira B without climate control (automatic aircon):

Zafira B Heater Blower Resistor
A Zafira B heater blower resistor

Our first Impressions

Anyone familiar with heater blower resistors only needs to glance at this resistor to see it is of an old fashioned design, which was mostly phased out around the year 2000.
Closer inspection also reveals a primitive solution for the thermal fuse - a soldered joint.
(Circled in the above example - it has already blown.)
Most heater blower resistors on modern vehicles without digital air con look like the example below:

Heater blower resistor
A typical example of a more recent style of heater resistor, - this one is from a Corsa D
Its "microtemp" thermal fuse can be seen sited at the top.

These later style resistors are of a more unified and encapsulated design that don't have individual resistors, but use coils of resistive wire that are embedded in a ceramic material, which distributes the generated heat more evenly so it does not get as hot.
They also use a "microtemp" thermal fuse which blows at an accurately preset temperature.
This style of blower resistor, however, does fail also, and they often lead to their connector plug burning out.
Fires as a result, though, are rarely, if ever, the result.
So possibly it is the result of using these old style resistors with primitive thermal fuse that is causing the fires?

Further Investigation

There have been many reports of blower motors becoming partially seized because of water ingress, and Vauxhall are known to be fitting "rain shields" below the scuttle cover, and replacing all blower resistors and pollen filters, and also, if the current drawn on speed 1 exceeds 4.5 amps, they are replacing the blower motor.
There have also been reports of charred / burnt pollen filters and of the resistor heat shield falling off.
There have also been reports of Climate Control models setting on fire from the glove box area.

What might be happening?

From our experience with heater blower resistors, we know that a common cause of failure is usually not just that the resistor "fails" - there is generally an underlying reason.
The way that these systems work is that the heater blower resistor is used to step down the power to the fan motor.
The heater blower resistor gets hot as a result. This is normal (if wasteful)
To stop it getting too hot, the car's designers situate it in the flow path of the blower fan.
However, if the flow path becomes restricted, maybe because of a blocked filter or perhaps autumn leaves in the inlet vents, then the resistor will get get hotter and hotter.
In addition the blower fan will be working harder, trying to push air through a restricted opening, and will start to draw more electrical current, which leads to the resistor get hotter still.
The same scenario can result from a fan motor that has developed partly seized bearings, maybe through water ingress.
Whatever the exact cause, something has to give.
In theory, the resistor should "self destruct" before it can do too much damage because it is fitted with a thermal fuse that should blow if the temperature exceeds a certain value.
We have also examined the electrical circuit for the blower motor and have discovered that the main fuse is rated at 40A, and that this will allow the cable (rated at 39A @20C) to be overloaded for up to 10 minutes at 54A before it blows, whereas we would expect the design to allow a safety margin of 25%.

Conclusions.

We suspect that the pollen filters and/or airways are becoming blocked, and also that water is entering the fan motors, causing them to draw excessive current.
We also suspect that genuine original blower resistor thermal fuses are unreliable, not "blowing" as they should, allowing an excessive build up of heat, resulting in the dashboard soundproofing catching fire.
We also suspect that there may be instances where the blower motor draws enough current to overheat the wiring before the fuse has time to blow. This would also affect the Climate Control versions, that Vauxhall currently have excluded from the safety recall.

Our recommendations to owners

1. If you haven't already been contacted by Vauxhall / Opel, contact them immediately to book your free recall.
2. Inspect your ventilation system air vent inlets at the base of the windscreen, and ensure they are not blocked with leaves etc.
3. Use your blower as little as possible, and only ever on setting 4 (the fastest), as no current passes through the heater resistor resistors on this setting.
Be especially wary if there are strange noises from the dashboard area whilst the blower fan is on.
4. If you ever see or smell smoke, turn off the heater, pull over as soon as possible and open a door to ensure you do not get trapped inside the vehicle. Then turn off the ignition.
5. Continue to regularly inspect and keep clear your heating system air vent inlets even after your vehicle has been recalled and rectified.
6. Join the Zafira Fires Facebook group to keep abreast of the situation, and get advice from other members.

If you don't want to wait for Vauxhall, either DIY, or contact an independent garage to carry out the following:
* Check your pollen filter and replace it - or just totally remove it to permanently improve the safety of your system.
You Tube - Change pollen filter on Zafira B
Out of interest, the blower resistor is partly visible in the upper centre at 4:35 / 4:53
* Check your blower motor...
Testing Zafira amps at 40A fuse
Remove 40amp fuse (top left hand side of fuse box under the bonnet, in fuse box) and place your ammeter terminals at the exposed terminals as shown.
Set the blower speed to "1", and if the measured current is more than 4.5A, you need to replace your blower motor.
* Replace the 40A fuse with 30A or 35A. This will give you added protection if your blower motor starts to draw more current than normal.
* Waterproof your blower motor...
Ensure the scuttle cover is correctly located, and is sitting flush and is not loose or damaged, otherwise water may find its way into the fan motor.

If for some reason you aren't able to get Vauxhall to repair your vehicle for you, you can purchase a new replacement resistor pack from us, with or without the end of the loom that plugs into it.



Please note whilst these recommendations are provided in good faith, we cannot be held responsible for any loss relating to the information we have provided.

 

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