Technical Heater issue

[Ant39]

Hi everyone,
Hoping somebody has come across this issue before since I'm now lost on what to attempt next.
For a while now setting 1-3 wasnt working on the heater so I eventually replaced the resistor and this got it working again right away.
24 hours later it blew again and stopped. Took out the heater motor and it did look quite corroded in some areas so I fitted a new heater motor and a new resistor.
Worked again however about 2 weeks later it's gone again.
I've had a look through all of the connections and none of them are burnt, as far as i can tell there doesnt seem any issues with the wiring which may cause a short.

Anyone able to offer some insight on this as to why the resistor keeps blowing? Both times I bought genuine to avoid issues like this.

Thanks in advance.

 

[RalphM]

Does it have a pollen filter? if so check it's not blocked not sure on your car
but many cars use the air flow through the heater to cool the resistor pack
so if the filter is blocked the pack can over heat.

 

[varesecrazy]

Is this a basic dash model with 4 fan speeds?

So you seem to have replaced the Fan motor
And the Resistor Pack

No mention of the wiring loom that links switch to resistor pack..

 

[Ant39]

It had a new pollen filter put in when it was last serviced in November.

It does have 4 fans speeds, I had inspected the loom and there are no breaks, exposed wires or burns though so hadn't looked to replace since there's nothing visibly wrong at least.

Cheers

 

[Mike1alike]

Remove the pollen filter and check the box for dead leaves that could have fallen inside. Something is not good there and is causing the problem. Can you mesure with a multimeter the DC voltage you get on those wires? And mayby the wires are "burned", I dont't know for sure, but could be the case that the wires are supposed to have a resistance, can you mesure with the multimetre [Ohms] if they do have any resistance?

 

[Mike1alike]

Or mayby the new resistor you bought is of lower amperage than the original. This is a reason for it to burn so fast. Do you still have the original to check the amperage [A]?

 

[OldEngineer]

The speed is regulated on the earth side so you ought to be able to test by taking a wire to earth

 

[Mike1alike]

The speed is regulated on the earth side so you ought to be able to test by taking a wire to earth

Is that true? So then, the resistor regulates the earth, so you have to connect the earth wire to the resistor. Ant39, maybe you did put the wires backwards. Could it be? If so, it is a reason for resistor to get burned.

 

[OldEngineer]

This is the wiring diagram showing the live side of the Heater Blower Motor coming straight from the fuse box. Then all the switching of the Earth Side...