P38A Fan speed on the heater

The fan speed is like dialing forever. My guess is the connections need cleaning. Will Maplins Switch Cleaner on a cotton bud do the job or is there something better you would recommend?

Funny, mine is the same never gave it a thought spends most of its time in auto

Mine's a bit like that too. Wheeling round and round without doing much.
Interestingly, when I popped the dial off to change the bulb, it started working perfectly. You could try that!

Fan speed is dependent on temperature as measured by sensor on matrix inlet pipe. Even if you set fans at full speed they will not come on at full speed until the coolant temp reaches a certain level.

brianp38dse said:

Funny, mine is the same never gave it a thought spends most of its time in auto

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Mine works perfectly but I almost never take it out of Auto except when I press Prog.

Like some of us has pointed out though, you spin it and spin it and it will eventually raze the or lower the fan speed, its not like you turn it up or down a notch and ir responds, you have to spin it (almost) to make it change the speed

wammers said:

Fan speed is dependent on temperature as measured by sensor on matrix inlet pipe. Even if you set fans at full speed they will not come on at full speed until the coolant temp reaches a certain level.

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Setting fan speed by turning adjustment knob overrides all automatic behavior. Turn it to maximum speed and relays in bower motors are engaged giving full voltage.

N2O said:

Setting fan speed by turning adjustment knob overrides all automatic behavior. Turn it to maximum speed and relays in bower motors are engaged giving full voltage.

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Nope.

Clean contacts. Then check HEVAC sensors.... all of them. Then turn knob slowly so ECU can catch up with it.

If you have to turn the knob loads of times, then chances are it's the contacts on the board are dirty and the wiper on the back on the rotary knob (the clear bit inside - not the cover that you pull off - so have to dismantle the unit.

It's one of the things I do on all the HEVAC units that I service, and pretty much all of them are tarnished, and the tracks on the board are dirty.

To clean the board, I use contact cleaner/isopropyl alcohol, and a cotton bud. To clean the metal wiper, I use high grit sandpaper, or emery cloth.

On my website, on my 'Technical Information' page there's instructions for installing my pixel fix shows the unit being stripped apart and the track on the board/and the wiper that gets dirty.

I had when I first got mine. Put it on max and it was like an asthmatic snail. Took both cabin filter covers off and there was that much crud and rubbish built up it was horrendous. New filters and a goot blast with the vacuum and all good.