8 replies to this topic

[The-evil-GT]

I have a fault with my 1979 1275gt where the ignition light stays on constantly , even when the key is turned to off , it goes out when I removed the plug to the alternator and when I removed the brown wire with the large spade connector from the starter solenoid ( I’ve been told it’s the feed for the voltage stabiliser ) I’m using a mini spares high torque stater motor with with the later solenoid in conjunction to the original wing mounted one . Could it be that I just haven’t added the ring terminal to the second solenoid or is their something more serious happening . Any help would be greatly appreciated.

[Spider]

If you disconnect the Brown / Yellow Wire from the back of the Alternator, the Lamp should go out.

Then, with the Key OFF, earth that wire and see if the Lamp comes on (it shouldn't). Then try again with the Key ON in the Run position, the Lamp should then come on.

 

This is to check that Lamp Circuit is working as it should be.

 

If that checks out, I'd say the regulator in the Alternator, at least in part, is karput.

[3VILC]

Sounds like you somehow have power to the alternator all the time, or the charge wire is on the wrong alt terminal if thats possible. I'm sure someone will correct me not sure on a 79, but from memory the original starter solenoid terminal is just a junction box for all the battery connections, one big brown wire feeds the car circuits and or fusebox input, the other is the charge wire from the alt. Doesn't help much, but if the lights on when the keys off you've got something connected wrong somewhere, but as mentioned this may be an internal fault in the regulator if you haven't moved any wires recently

[The-evil-GT]

Sorry for the really late reply , I checked the lamp circuit as suggested above and it is that circuit that has failed I believe , does anyone have any guesses as to why that would be the culprit, could it be a dodgy voltage regulator or some such

[The-evil-GT]

Only other thing I have noticed as well is that the side lights have stopped working

[Ethel]

The ignition light sits inline between the alternator (brown/yellow) & ignition live (white). The white should only be live with the ignition on & the B&Y acts like an earth without the alternator spinning, when it turns, the wire is at the +ve voltage being generated.

 

You need to figure out where the light is getting +ve voltage from & where it's earthing. A meter would be useful if you have one.

 

As said, the alternator is connected to the solenoid battery cable terminal by a pair of thicker brown wires - if the alternator is faulty they could be supplying 12v to the brown/yellow. You'd have stopped that by pulling the alternator plug, but that would also stop the brown/yellow earthing. To figure out which, bridge the connectors in the plug, that will feed 12v to the ignition light and keep it from earthing as intended. So, if it lights up you'll know the alternator is faulty and there's a short on the ignition switch side of the bulb. If it doesn't light then it suggests something is earthing via the ignition light.

 

It could be a faulty ignition switch - unplug its connector where it exits the steering column cowl.

 

You may have wrong/ faulty connections at the solenoid/starter - look for a white/yellow wire & unplug it.

 

It could be the printed circuit for the instruments, especially if it got damp.

 

The side lights are connected to dash illumination so they could be a source of 12v, but you'd also need a faulty light switch - worth looking at their fuse all the same. Look for the fuse with a solid red wire on one side (+) & red/green on the other.

 

 

.....the ignition wiring does have a normal earth - with the key out of the ignition (alternator plugged in, light on) remove the white wire from the coil's +ve terminal & see if that kills the light.

[The-evil-GT]

Hi guys , I earthed the oil pressure switch today and both lights now come on and stay on , I’ve tested a couple of other circuits to eliminate some possibility, when I remove power to the fuse block at connector 3 the lights go out but if I leave power and remove the fuse they stay on , I though it could be the headlight flasher but removed it and the lights stayed on , I suspect it could be the voltage stabiliser but I really am not sure . Any help is greatly appreciated. Additionally I’d like to thank everyone who has contributed previously, it’s tremendously helpful so thank you all so much

[Spider]

I'd probably start by looking at the PCB on the back of the Instruments.

[The-evil-GT]

The pcb is a brand new one from mini spares