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The red one was originally an oil pressure light. Comes on with ignition switch, goes off when running (over 7lbs per sq in).
 

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There's no charging light on any unit Meriden Triumph. Any light that comes on when you turn the ignition on is oil pressure and should go out as soon as the engine starts - if it stays on, turn the engine off and don't restart until you've thoroughly checked the oil system
 

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Discussion Starter #4
Thing is guys I can't locate the switch in the parts book and I can trace no wires that would allow a oil pressure switch. Where I see others mounted my manual call for a plug. I have installed an oil pressure gauge.
 

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Well that's a bit of a mystery then! If you've installed a pressure gauge it must take its feed from where the warning light switch would normally go. So what is that light connected to? No neutral switch on anything pre-79; headlight warning? Only if wrongly wired or if your headlight is permamnently on main beam! That's me out of ideas...

At least, if you have a pressure gauge, you know you've got nothing to worry about there!
 

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Discussion Starter #6
Ignition light and headlight on. This is my first Triumph and I keep reading about the switch but can't find a reference in the parts book for my bike.

I've learned a lot about this bike while redoing it...mainly, you're never done.
 

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I went through the same problem with my 1969 T120R. First off, I still have not seen any wiring diagram for 1968, 1969 or 1970 that shows the wire going from oil pressure switch ( leading edge of timing cover ) to the ignition light. All diagrams simply show a red wire going to ground. Second, the parts book can be misleading on the oil pressure switch because there were two of them - one tapered and one straight. I purchased a replacement according to my parts book and it was the incorrect one, ordered the other and it fit like a glove. Inefficient way of getting the correct part but at least I've got it right now. Here's how it works - hot is, I believe, a white wire going to the ignition bulb and the ground wire is red w/black stripe & goes to the oil pressure switch. Oil pressure switch is grounded with bike off which completes the circuit when key is turned and bulb lights. Kicking over creates oil pressure which breaks the ground contact, light goes off. If you're running and lose oil pressure ground is once again made and light goes on, you should shut down immediately. You've got a gauge so you'll know in any case. Lastly, I know what the manual says. But a green light meaning DANGER and a red light meaning your high beams are on is backwards in my mind. So my setup is left bulb is red and is my ignition/oil pressure light, right bulb is high beam indicator & is green. Hope this helps. Oh, one last thing. Do NOT overtighten the oil pressure switch. Mine is on with some teflon tape and it's solid as a rock with no leaks.
 

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To follow up - part number for Tapered oil pressure switch is D2133 and for straight is D3719. At BritCycle the part numbers are 60-2133 and 60-3719. 3719 fit my 69 Bonneville.
 

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Yours is probably blanked-off like this: [below the oil-pressure relief valve]


If you buy a switch, it works by switching-off earth, when the engine oil pressure rises.
The wire from the switch goes to one side of the red warnig light.
Therefore the live (white?) goes to other side of the red warning light.
 

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'68 didn't have an oil light or pressure switch.
They use a 3/8" X 26 tpi thread where the plug fits in the timing case.
A 27 tpi switch or oil gauge fitting is to big to fit this thread.

You could make a one-off fitting with 38 x 26 thread into the case and 1/8" NPS or NPT female thread to suit the switch/gauge.

Far easier to just tap out the thread in the case.1/8" NPT tapered thread is more likely to crack and split the case than 1/8" NPS.
 

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Agree with Mr Pete, up to '68 there was no oil pressure switch, '69 onwards did. Easy to check....... if you have a blanking plug at the front of the timing case, you don't have an oil pressure switch.
 

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Just to add my 2 cents worth --- section H15 Workshop manual for Unit construction 650 cc twins -- states :--' TR6C models do not have the oil pressure switch fitted at the front of the timing cover. On such machines, the red warning light is connected into the ignition circuit so that this light goes on when the ignition is turned on and stays on as long as the ignition is turned on , irrespective of whether the engine is running or not.'
Just something to think about.
 
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