[Navcomic]

Hello from the UK.
My wife's B-Max has now got no speeds on the fan except position 4. I have checked the pollen filter - a suggestion on another forum - and that is fine. As the resister pack has been previously changed under warranty, I suspect the resistor pack has burnt out.... again. This problem might be caused by underrated wattage ratings of the resistors in the pack. I have not had the unit out yet to have a look but does anyone know the value of the individual resistors in the pack? I could then try again with up-rated resistors making sure that any additional heat from the resistors does not cause problems with the pack housing.
Incidentally, when the car was last repaired, the Ford agent said we must not run the heater for too long on one speed setting....... 🤣
Thanks for any help.

 

[Gremlin]

a very quick search found this vid that should answer your question and more.

 

[Navcomic]

Many Thanks. I have a feeling this problem is being caused by insufficient air being passed over the resister pack by the heater air flow - especially on the lowest speed setting - with the result the resistor elements burn out. It might also thus be critical as to how blocked the pollen filter becomes over time. I might try running without the filter as I do not want to start messing about with any manifold adjustments. To actually replace the resistors might be possible once I have got a replacement unit, measured the resistor values and then substitute in some beefy discrete resistors based on the wiring diagram from the video or figuring out the circuit before the replacement unit next fails(!). Thanks.

 

[Navcomic]

Many Thanks. I have a feeling this problem is being caused by insufficient air being passed over the resister pack by the heater air flow - especially on the lowest speed setting - with the result the resistor elements burn out. It might also thus be critical as to how blocked the pollen filter becomes over time. I might try running without the filter as I do not want to start messing about with any manifold adjustments. To actually replace the resistors might be possible once I have got a replacement unit, measured the resistor values and then substitute in some beefy discrete resistors based on the wiring diagram from the video or figuring out the circuit before the replacement unit next fails(!). Thanks.

Today: I have changed the resister pack and my better half has been instructed to not run the heater on position 1 as there is undoubtedly insufficient airflow to cool the resistors in the pack when the heater is in position 1. Whether this low airflow is due to original maladjustment of the heater manifold system I do not know - and I do not intend to find out!
Incidentally, does anyone know the direction of the air flow arrow marking on the pollen filter? Should it face into the cabin or towards the firewall? I vacuumed the filter when it came out for checking and the design appears to be the same on both side but if there is a correct way round in the heater housing, I ought to have it correct. (I forgot to note it down when I took the filter out. Doh!)

 

[pegleg]

The arrow on the pollen filter should be on the top and face inwards towards the cabin.
Its a pity the heatsink isn't larger for the resistor pack! The resistors get the hottest at the slowest speed; therefore you've been correctly informed about position 1. If you ran the motor on 4, the pack would last forever!
Doubt the motor would though!

 

[Navcomic]

The arrow on the pollen filter should be on the top and face inwards towards the cabin.
Its a pity the heatsink isn't larger for the resistor pack! The resistors get the hottest at the slowest speed; therefore you've been correctly informed about position 1. If you ran the motor on 4, the pack would last forever!
Doubt the motor would though!

Sincere apologies for the slow reply. I have checked it now and all was OK (by chance!). I have also added a dymo arrow behind the plastic cover to indicate which way for next time. (I have also added a warning not to run in posn 1 for the next garage guy who changes the filter!). All in all, this seems to be not one of Mr Ford's finest moments. Thanks again for your help.