Heater Switch Removal

[Scuba Joe]

Can anyone recommend how to remove the heater fan 2 speed switch from the dash? the nearest I have got is to remove the radio and poke around behind the switch - but no success. I'm quite concerned about ruining the walnut facia. Surely there must be an easier way than removing the whole dash?? (there again it is a TVR...)

Thanks

[GreenV8S]

Which model is it? There are several different dash designs.

[AutoAndy]

Your profile says it’s an S3.

Then have you undone the two screws at the back of the center console...near the seat backs?

The centre console than lifts out (as far as the electrical cables allow) and you can get to the back...sort of...to the switches..

[Scuba Joe]

It is an S3.
Thanks, I'll hunt for the 2 screws!

[Scuba Joe]

So, Dash removed, switch removed, cleaned, tested and the switch is fine. So, anyone any other ideas why the heater blower only intermittently works at random times only??

[phillpot]

The fan motor has Phosphor bronze bushes, it's not un-common for these to go dry, does the fan "squeal" at all when it does run?

All it needs is a drop of oil........ and a couple of days to strip the dash out to get at it

[Bobhon]

Could be that the brushes in the motor have worn out or are clogged up and need either replacing or cleaning up.

The slow speed is achieved by putting the current through a big resistor. These can overheat and break down losing your slow speed.

Or it could be the wires in the connector to the motor breaking down giving an intermittent contact. With the centre console out you can probably get to the motor connector in the left hand footwell. Put your hand around the back of the heater box to the motor and trace the cables back to the connector. You can the see if the current is getting to the connector.

If it is then you may need to drop the motor out. It comes out rearwards through the heater box. You have to remove the air intake grille on the rear of the heater box. Then undo the fixings on the motor on the front of the heater box. The motor and fan unit then pulls out rearwards.

On my S2 I had to remove the whole dash to get the motor out. I don't know if you can get it out on the S3's and later by just removing the centre console.

Edited by Bobhon on Sunday 22 October 20:16

[Scuba Joe]

[quote=phillpot]

does the fan "squeal" at all when it does run?

No squealing at all, it seems to work on low and high speed, but only at random times. last time, with ignition on it worked great, cranked the car and it stopped and after turning off the engine still didn't work. I know it will work in the future, but not just when I want it to..

[Scuba Joe]

Bobhon said:

Could be that the brushes in the motor have worn out or are clogged up and need either replacing or cleaning up.

The slow speed is achieved by putting the current through a big resistor. These can overheat and break down losing your slow speed.

Or it could be the wires in the connector to the motor breaking down giving an intermittent contact. With the centre console out you can probably get to the motor connector in the left hand footwell. Put your hand around the back of the heater box to the motor and trace the cables back to the connector. You can the see if the current is getting to the connector.

If it is then you may need to drop the motor out. It comes out rearwards through the heater box. You have to remove the air intake grille on the rear of the heater box. Then undo the fixings on the motor on the front of the heater box. The motor and fan unit then pulls out rearwards.

On my S2 I had to remove the whole dash to get the motor out. I don't know if you can get it out on the S3's and later by just removing the centre console.

Edited by Bobhon on Sunday 22 October 20:16

Well....it was a big job just getting the centre console out. Not the actual removal, but as all the wires to the switches are short, they had to be reconnected with little access and even more little view. I will check the blower connections first if I can get to the, but I am lead to believe that its a full dashboard removal on an S3. Not so keen on that!

[Steve_D]

Those switches can be a right pain to get clean and working reliably.
When you cleaned it did you dismantle it completely? If you did, did you also clean the pivot points of the contacts not just the contact points?

Steve

[Scuba Joe]

Hi Steve,

I believe the switch is fine. I used a multimeter and tested the voltage etc which was showing correctly after a clean.

[Steve_D]

It is still possible the switch will seem fine when tested with a multimeter but the contacts are burnt or dirty and will not pass the heavier current the fan motor requires. These fan motors, even when new, are amongst the highest current users on a car. Now that they are old and the bearings are drying out (hence the earlier question about 'squeal') the fan will be drawing even higher current.

Steve

[glenrobbo]

Cue a lovely schematic electrical diagram containing several relays, courtesy of Penelope Pitstop?

[v8s4me]

Steve_D said:

Those switches can be a right pain to get clean and working reliably.
When you cleaned it did you dismantle it completely? If you did, did you also clean the pivot points of the contacts not just the contact points? Steve

They are fiddly but I've done two complete sets of them now and they aren't that bad so long as you're careful and take your time. Good point from Steve about the pivot points. Also be very careful with the little spring loaded pins DON'T LOSE THEM!

[GreenV8S]

If the problem is only in the switch, you could prove that by measuring a voltage drop across it while the fan was on, or showing the fan ran reliably when the switch was bypassed. There are plenty of other reasons for intermittent problems and I'd want to confirm the switch was actually the problem before I took it apart.

[Griffinr]

glenrobbo said:

Cue a lovely schematic electrical diagram containing several relays, courtesy of Penelope Pitstop?

No relays are old hat you need Pulse width modulation or DC chopper control.
When chopper is ON motor gets supply but when chopper is off motor does not get the supply. So as shown lets us say chopper is on for Ton time and it is off for Toff time. So depending upon the Ton and Toff time the DC voltage applied to motor is

Vdc = [Ton / (Ton + Toff)] × Vfixed

But Ton + Toff = Ttotal

So Vdc = [Ton / Ttotal] × Vfixed

Here Ton / Ttotal is called duty cycle. So as duty cycle is more the average DC voltage supplied to motor is more and so speed of motor is increased. So as duty cycle is varied by varying on and off time of chopper, the speed of motor can be varied.

Edited by Griffinr on Tuesday 24th October 14:00

[phillpot]

All this fannying around taking a fiddly little switch to pieces which may be perfectly alright (until you take it to pieces), would it not be easier to by-pass it to prove yea or nay?

Edited by phillpot on Tuesday 24th October 23:04

[v8s4me]

Where's the fun in that?

[Penelope Stoppedit]

Good Evening Scuba Joe, I hope you have sorted your problem, if you are still searching for the fault my following advice may help you
I think someone else has suggested something like this.
If the fault is very intermittent you will find it more easily by using the car with a multimeter connected into the circuit at the main blower plug or at the blower switch, at least you will see if the supply or earth to the blower box is vanishing now and then
You can even run wires from near to the blower box and from the switch to outside the center console and carry out several tests until proving what is failing or at least proving if the fault is in the box or outside the box
I hope you get this fixed soon

[Scuba Joe]

Thank you all for all the really helpful comments. I am going to try the connector on the actual heater blower with a separate power supply etc, as that will rule out the switch (or in...) and I believe I can get to that without talking the car to pieces again. I'll report back!