This refers to a car switch but is not really a car specific problem.

My car heater switch has 4 power positions, if the aircon is switched on
it starts when the heater switch is turned to position 1 through to 4.

Now for some reason my heater is not working on position one although
the aircon kicks in, the heater works fine on positions 2 through to 4.

This has thrown me, if nothing worked on position 1 then I could
understand it but if anyone can give me an idea I'd appreciate it.

Geoff Lane

On Mon, 23 Feb 2009 19:03:59 +0000, Geoff Lane
wrote:

This refers to a car switch but is not really a car specific problem.

My car heater switch has 4 power positions, if the aircon is switched on
it starts when the heater switch is turned to position 1 through to 4.

Now for some reason my heater is not working on position one although
the aircon kicks in, the heater works fine on positions 2 through to 4.

This has thrown me, if nothing worked on position 1 then I could
understand it but if anyone can give me an idea I'd appreciate it.

Geoff Lane

There will be a resistor pack to regulate blower speed. The first resistor is
dis. If you let us know what car it is, someone will be able to tell you where
it's mounted.

Andy C

On 23 Feb, 19:11, Andy Cap wrote:

There will be a resistor pack to regulate blower speed. The first resistor is
dis. If you let us know what car it is, someone will be able to tell you where
it's mounted.

These resistors run hot, so they're almost always mounted in the fan's
own airflow, usually right next to it.

"Andy Dingley" wrote in message
...
On 23 Feb, 19:11, Andy Cap wrote:

There will be a resistor pack to regulate blower speed. The first
resistor is
dis. If you let us know what car it is, someone will be able to tell you
where
it's mounted.

These resistors run hot, so they're almost always mounted in the fan's
own airflow, usually right next to it.

If it's a Ford, its right above the passenger footwell, fixed with a single
screw. Very common problem. Often caused by the pollen filter being blocked
and in need of renewal, restricting the airflow in the system, and not
properly cooling the resistor pack, which is, as Andy said, mounted directly
in that airflow.

Arfa

In message , Arfa Daily
wrote

"Andy Dingley" wrote in message
...
On 23 Feb, 19:11, Andy Cap wrote:

There will be a resistor pack to regulate blower speed. The first
resistor is
dis. If you let us know what car it is, someone will be able to tell you
where
it's mounted.

These resistors run hot, so they're almost always mounted in the fan's
own airflow, usually right next to it.

If it's a Ford, its right above the passenger footwell, fixed with a single
screw. Very common problem. Often caused by the pollen filter being blocked
and in need of renewal, restricting the airflow in the system, and not
properly cooling the resistor pack, which is, as Andy said, mounted directly
in that airflow.


For reference - a Ford Focus (circa 2001) blower motor circuit and
position of the resistor pack can be found at
http://www.amac.f2s.com/Focus1/

If (and it's a big if) the original poster's car has the same or a
similar circuit then a failure of one of the speed control resistors
would cause a permanent failure, even when the A/C was turned on.

Still assuming a similar circuit, the explanation would be the switch
has mechanically failed in that position. In the circuit shown in the
above link, the slowest blower motor position is also connected to the
heater control module and if by turning on the AC that connection
(labelled Cb) is switched to 0V then the blower motor will again work in
the slowest position. i.e. there are two methods of switching the bower
motor on in it's slowest setting and the AC probably overrides the
switch.

The AC probably does override the switch in order to turn on the blower
motor when the switch is in the off position.

If its a Spanish built Vauxhall then the connector has probably fallen
off the back of the switch, or is just about to

--
Alan
news2006 {at} amac {dot} f2s {dot} com

On Feb 23, 7:11*pm, Andy Cap wrote:

My car heater switch has 4 power positions, if the aircon is switched on
it starts when the heater switch is turned to position 1 through to 4.

Now for some reason my heater is not working on position one although
the aircon kicks in, the heater works fine on positions 2 through to 4.

There will be a resistor pack to regulate blower speed. The first resistor is
dis. If you let us know what car it is, someone will be able to tell you where
it's mounted.

Sorry for delay in replying.

Car is a Nissan Micra.

Geoff Lane

Now for some reason my heater is not working on position one although
the aircon kicks in, the heater works fine on positions 2 through to 4.

Resistor pack. Been there, done that.

Make of car?

Al.

"Al" wrote in message
. 4...
Now for some reason my heater is not working on position one although
the aircon kicks in, the heater works fine on positions 2 through to 4.

Resistor pack. Been there, done that.

Make of car?

Al.

On some Nissan cars the resistor card has two contacts that are bridged with
solder acting as a thermal fuse and these are a common source of failure on
these cards. Repair is to clean of the contacts and resolder.
Trevor Smith

On 24 Feb, 10:51, "Trevor Smith" wrote:
"Al" wrote in message

. 4...

Now for some reason my heater is not working on position one although
the aircon kicks in, the heater works fine on positions 2 through to 4..

Resistor pack. Been there, done that.

Make of car?

Al.

On some Nissan cars the resistor card has two contacts that are bridged with
solder acting as a thermal fuse and these are a common source of failure on
these cards. Repair is to clean of the contacts and resolder.
Trevor Smith

Thanks for all the suggestions folks, the resistor is easy to get at
right by the heater blower motor.

New replacement about £30 so not too expensive, could try a breakers
but honestly how much can I save and is it worth the aggro.

Geoff Lane

On Feb 24, 9:38 am, Al wrote:
Now for some reason my heater is not working on position one although
the aircon kicks in, the heater works fine on positions 2 through to 4.

Resistor pack. Been there, done that.

Make of car?

I have a similar problem on a Mazda 626. The resistor pack has failed
for the second time. A new pack here in NZ costs the equivalent of UK
50 pounds. Why are they so expensive, and why can't I just cobble up a
new pack from some huge resistors that I have lying around?

"Matty F" wrote in message
...
On Feb 24, 9:38 am, Al wrote:
Now for some reason my heater is not working on position one although
the aircon kicks in, the heater works fine on positions 2 through to 4.

Resistor pack. Been there, done that.

Make of car?

I have a similar problem on a Mazda 626. The resistor pack has failed
for the second time. A new pack here in NZ costs the equivalent of UK
50 pounds. Why are they so expensive, and why can't I just cobble up a
new pack from some huge resistors that I have lying around?

Why indeed ... ?

Arfa

I have a similar problem on a Mazda 626. The resistor pack has failed
for the second time. A new pack here in NZ costs the equivalent of UK
50 pounds. Why are they so expensive, and why can't I just cobble up a
new pack from some huge resistors that I have lying around?

You can. Bear in mind that the resistor pack runs so hot on some makes
(Audi and BMW spring to mind) that the solder will melt! ISTR that when I
fixed my BMW pack I just had to re-crimp the connections.

It seems terribly inefficient to me to have red hot resistors when there
are better ways to control fan speed. But it's the cheapest option for the
manufacturer

Al.

Al wrote:
I have a similar problem on a Mazda 626. The resistor pack has failed
for the second time. A new pack here in NZ costs the equivalent of UK
50 pounds. Why are they so expensive, and why can't I just cobble up a
new pack from some huge resistors that I have lying around?

You can. Bear in mind that the resistor pack runs so hot on some makes
(Audi and BMW spring to mind) that the solder will melt! ISTR that when I
fixed my BMW pack I just had to re-crimp the connections.

It seems terribly inefficient to me to have red hot resistors when there
are better ways to control fan speed. But it's the cheapest option for the
manufacturer

Al.
Actually, these days it probably isn't. But inertia and total lack of
comprehension about electronics by auto designers is a key issue.

As an electric toy plane flyer, I can get an infinitely variable PWM
controller for about 50A for under 30 quid, retail. Couple that to a 5
quid 'servo tester' and you can have infinitely variable and very cool
running fan control for less than the cost of the spare resistor pack....

In article ,
Al wrote:
I have a similar problem on a Mazda 626. The resistor pack has failed
for the second time. A new pack here in NZ costs the equivalent of UK
50 pounds. Why are they so expensive, and why can't I just cobble up a
new pack from some huge resistors that I have lying around?

You can. Bear in mind that the resistor pack runs so hot on some makes
(Audi and BMW spring to mind) that the solder will melt! ISTR that when
I fixed my BMW pack I just had to re-crimp the connections.

It seems terribly inefficient to me to have red hot resistors when there
are better ways to control fan speed. But it's the cheapest option for
the manufacturer

What BMW do you have? Most for the last ten years or more don't use a
resistor pack - it's an infinitely variable speed controller.
Which is even less reliable than resistors...

Al.

--
*Learn from your parents' mistakes - use birth control

Dave Plowman London SW
To e-mail, change noise into sound.

What BMW do you have?

It was an E30 320i of 1985 vintage. Excellent car overall. Only niggle in
11 years of ownership was a dodgy FPR that took months to diagnose and was
fixed in minutes with a 10 quid second hand one off of ebay

Scrapped it recently even though it was running happily. Getting a bit
rusty, and I just didn't need it any more. Had hoped it could be used for
banger racing but apparently it's too big/powerful/whatever

Al.

Al wrote:
Now for some reason my heater is not working on position one although
the aircon kicks in, the heater works fine on positions 2 through to 4.

Resistor pack. Been there, done that.

Make of car?

Posted reply from google account and it showed a different user name so
contributers may not have noticed my reply;

My car is a Nissan Micra.

Geoff Lane

on 23/02/2009, Geoff Lane supposed :
This refers to a car switch but is not really a car specific problem.

My car heater switch has 4 power positions, if the aircon is switched on it
starts when the heater switch is turned to position 1 through to 4.

Now for some reason my heater is not working on position one although the
aircon kicks in, the heater works fine on positions 2 through to 4.

This has thrown me, if nothing worked on position 1 then I could understand
it but if anyone can give me an idea I'd

The very basic fan speed controllers use large wirewound resistors to
control the speed and these often burn out or develop poor connections.
If your a/c runs the fan on its lowest speed without you needing to
alter the fan speed setting, then that might indicate a fault on the
switch or wiring from switch to resistors. Either way look for charred
or discoloured connections.

A more sophisticated system for fan speed control uses a pulse width
modulated controller instead of resistors and these are usually fitted
on the climate control type of system.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk