Heater Fan Switch
Discussion
Does anybody have a 350i heater twin speed fan switch please? Mine is going to give up soon.
I have read other threads that say that these are TR7 switches but which one?
http://www.rimmerbros.co.uk/Item--i-GRID006239
Main headlamp switch? or is this just a straitght on/off type? Doesnt say
http://cgi.ebay.co.uk/TRIUMPH-TR7-TR8-LIGHT-HEADLA...
I have read other threads that say that these are TR7 switches but which one?
http://www.rimmerbros.co.uk/Item--i-GRID006239
Main headlamp switch? or is this just a straitght on/off type? Doesnt say
http://cgi.ebay.co.uk/TRIUMPH-TR7-TR8-LIGHT-HEADLA...
From memory, the heater fan switch and the main light switch are the same internally, the only difference is the window bearing the legend to tell you what the switch is for - although the part numbers are different.
The switch has two sliding (or 'rocking') contacts; in the OFF position both are open, in the first ON position one is closed and the other open and in the second ON position both are closed. So in the case of the lights switch, one contact puts the sidelights on and the other feeds the headlamps. As a fan switch, the first contact supplies a 'dropper' resistor (on early cars a few feet of wire wound into a coil, on later cars it was built-in to the motor) that wastes electricity in order to slow the motor down; the second contact merely shorts out the resistor, allowing full voltage to the fan.
Early cars don't seem to suffer from switch failure, but on later cars Smiths started using a more powerful motor that takes rather more current than the switch is happy with and it melts the switch when used on full speed
All the switches in the range use common components so it's possible to strip any one switch to repair most of the others.
It's a simple mod. to add a relay so that it, and not the switch, takes the full current of the motor. That way the switch should last forever
The switch has two sliding (or 'rocking') contacts; in the OFF position both are open, in the first ON position one is closed and the other open and in the second ON position both are closed. So in the case of the lights switch, one contact puts the sidelights on and the other feeds the headlamps. As a fan switch, the first contact supplies a 'dropper' resistor (on early cars a few feet of wire wound into a coil, on later cars it was built-in to the motor) that wastes electricity in order to slow the motor down; the second contact merely shorts out the resistor, allowing full voltage to the fan.
Early cars don't seem to suffer from switch failure, but on later cars Smiths started using a more powerful motor that takes rather more current than the switch is happy with and it melts the switch when used on full speed
All the switches in the range use common components so it's possible to strip any one switch to repair most of the others.
It's a simple mod. to add a relay so that it, and not the switch, takes the full current of the motor. That way the switch should last forever
Hi
Two speed fan?
All my wedges have the switch but none of them does it appear to work the two speed fan.
The first postion on the switch (On all three cars the FHC has two fans) the fans don't work, they only do when you put the switch in the second postion (Fully down.)
Strange that it the same on all the cars!
Can all four be broken?
Andy
Two speed fan?
All my wedges have the switch but none of them does it appear to work the two speed fan.
The first postion on the switch (On all three cars the FHC has two fans) the fans don't work, they only do when you put the switch in the second postion (Fully down.)
Strange that it the same on all the cars!
Can all four be broken?Andy
Mr Tank said:
Hi
Two speed fan?
All my wedges have the switch but none of them does it appear to work the two speed fan.
The first postion on the switch (On all three cars the FHC has two fans) the fans don't work, they only do when you put the switch in the second postion (Fully down.)
Strange that it the same on all the cars! Can all four be broken?
Andy
It can only be the user Andy, must be the way your holding your mouth.Two speed fan?
All my wedges have the switch but none of them does it appear to work the two speed fan.
The first postion on the switch (On all three cars the FHC has two fans) the fans don't work, they only do when you put the switch in the second postion (Fully down.)
Strange that it the same on all the cars!
Can all four be broken?Andy
Got the same on my Taimar but the SEAC has two speeds.
Oh begger just jinxed my self...TVR special I gess
You're not missing much Andy, high speed is as fast as it'll go! To get slow speed they just switched-in a resistor to slow the motor down. On early cars it was about 6 feet of normal wire wound into a coil and cable-tied to the back of the switch.
Later fan motors have the resistor built-in (or rather, -on) but the principle's the same.
Given that 'high' speed is about as effective as a fly's fart in a thunderstorm, being without low speed is no sacrifice
Later fan motors have the resistor built-in (or rather, -on) but the principle's the same.
Given that 'high' speed is about as effective as a fly's fart in a thunderstorm, being without low speed is no sacrifice
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