GeoffreyS Posted March 12 Report Share Posted March 12 When I turn on the headlights, the dash dial lights do not come on. The indicators, full beam and ignition lights on the dash work fine, but otherwise all gauges are dark. The rheostat turns, but nothing. Has anyone had an experience of this, please? Quote Link to post Share on other sites
Drewmotty Posted March 12 Report Share Posted March 12 Often caused by a dodgy rheostat. Turn it back and forth robustly to clean the track off. If that doesn’t work then short out the two wires on the back. If it still doesn’t work then you’re into tracing the supply back. As you don’t have any working it will most likely be a wire fallen off the supply on the back of the lighting switch. Quote Link to post Share on other sites
GeoffreyS Posted March 12 Author Report Share Posted March 12 Just now, Drewmotty said: Often caused by a dodgy rheostat. Turn it back and forth robustly to clean the track off. If that doesn’t work then short out the two wires on the back. If it still doesn’t work then you’re into tracing the supply back. As you don’t have any working it will most likely be a wire fallen off the supply on the back of the lighting switch. Thank you. I’ll see if I can do that. Quote Link to post Share on other sites
RobH Posted March 12 Report Share Posted March 12 Do the sidelights and number plate lamps work? Those come from the same fuse as the panel lights so if they don't work either, the fuse has probably blown or is making a poor connection. If they do work then either the rheostat or the feed to it is faulty. The schematic shows a join of the sidelight and panel light feeds where three red wires connect together - unfortunately I don't know where that is physically. Quote Link to post Share on other sites
GeoffreyS Posted March 12 Author Report Share Posted March 12 Thank you. Yes, the side lights and number plate lights work. Everything works except what is controlled by the rheostat knob. I just don’t know where to look. Thank you. Quote Link to post Share on other sites
harrytr5 Posted March 12 Report Share Posted March 12 Where are you Geoff ? Bypass the rheostat. Speedo and rev counter out. Disconnect the glove box stay. Take out the five securing screws. Pull dash forwards and you may have to undo the oil feed pipe for better access. You can then see where the wiring is on the rheostat and bypass it. Red cables to join red and white. Solder Bullet connectors and sleeves. Regards Harry Quote Link to post Share on other sites
BlueTR3A-5EKT Posted March 12 Report Share Posted March 12 (edited) I have a NOS tatty but never fitted Lucas 78490 rheostat. Dated 5/71 (May71) for CP TR5/TR6. i have cleaned the area that the part number is stamped on with a fibre glass brush to be able to read it Resistance test from off to 4.5 ohms. Using 200 ohm scale. Yours for £10.00 plus postage. Edited March 12 by BlueTR3A-5EKT Quote Link to post Share on other sites
GeoffreyS Posted March 13 Author Report Share Posted March 13 On 3/12/2024 at 10:03 AM, harrytr5 said: Where are you Geoff ? Bypass the rheostat. Speedo and rev counter out. Disconnect the glove box stay. Take out the five securing screws. Pull dash forwards and you may have to undo the oil feed pipe for better access. You can then see where the wiring is on the rheostat and bypass it. Red cables to join red and white. Solder Bullet connectors and sleeves. Regards Harry Hello Harry, Thank you for the information. I can follow what you instruct, but I think it is beyond my physical scope, sadly. I’m in Clerkenwell. Regards, Geoff Quote Link to post Share on other sites
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