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TR4a heater switch wiring


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Hi All (me again)

another little bug with my TR.

I'm guessing i have the wrong heater switch in the vehicle (see image) and I'm pretty sure it isn't wired in correctly either. 

 

Currently I have a red wire (Live) coming from the wire harness connection (Ignition on) and this goes to the switch shown in the pictures (has two pull-out positions) and this then connects to a black wire at the switch which comes out as live (umm) and then connects to one of the two white wires coming from the heater itself (The other is currently just loose).  

So 'm pretty sure this is all totally wrong (doesn't work at least that's for certain).

Before i go and buy a proper heater switch, how is it supposed to be wired in?

and can i test the heater without a switch ?

heater switch1.jpg

haeter switch2.jpg

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The wire colours make me think Mr Bodgeit has been at work here.  Feed should be green and red is reserved for the lighting circuits. A two-pull switch might imply a two speed fan but the original was only single speed.  Maybe that has been changed?

To check the fan I would first see whether either of the white wires has a resistance to earth.  if they don't it is odds on the fan is single speed and these are power and return conections.     Connect one to 12v and the other to earth and the fan should spin.  The direction of blow may change if the connections are reversed.

If they do have a resistance to earth (not a short circuit) they may be fast and slow power connections with the earth being through the fan metalwork.  Connecting either to 12v  should make it work.  

Let  us know what you find as that will determine how the switch needs connecting. 

 

 

 

 

Edited by RobH
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1 hour ago, RobH said:

The wire colours make me think Mr Bodgeit has been at work here.  Feed should be green and red is reserved for the lighting circuits. A two-pull switch might imply a two speed fan but the original was only single speed.  Maybe that has been changed?

To check the fan I would first see whether either of the white wires has a resistance to earth.  if they don't it is odds on the fan is single speed and these are power and return conections.     Connect one to 12v and the other to earth and the fan should spin.  The direction of blow may change if the connections are reversed.

If they do have a resistance to earth (not a short circuit) they may be fast and slow power connections with the earth being through the fan metalwork.  Connecting either to 12v  should make it work.  

Let  us know what you find as that will determine how the switch needs connecting. 

 

 

 

 

Thanks Rob. Fan works and doesn’t appear to be any resistance (assuming I’m using tester correctly). I’ll get a switch I guess it’s straightforward live in and live out. Thx again always so helpful on here. 

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Just now, Lockjack said:

Thanks Rob. Fan works and doesn’t appear to be any resistance (assuming I’m using tester correctly). I’ll get a switch I guess it’s straightforward live in and live out. Thx again always so helpful on here. 

Sorry forgot to ask I guess I have to try and find a green live (when ignition on only) within the harness?

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Yes a straight on/off switch will do it.  

Where you power it from depends where that red wire goes.  It might go to the fuse with other red wires on it and if so that's not a good place as that is the lighting circuit.  The feed should come from the fuse with green wires, originally via the feed to the instrument voltage stabiliser.  You can see that in the diagram that Ade linked to and it is possible thats where the red wire goes.

 

 

Edited by RobH
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2 minutes ago, RobH said:

Yes a straight on/off switch will do it.  

Where you power it from depends where that red wire goes.  It might go to the fuse with other red wires on it and if so that's not a good place as that is the lighting circuit.  The feed should come from the fuse with green wires, originally via the feed to the instrument voltage stabiliser.  You can see that in the diagram that Ade linked to and it is possible thats where the red wire goes.

 

 

Cool. Will get crawling and testing. Thx everyone 

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