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MG MGB Technical - Heater light not working.

The heater light has stopped working on my 78 gt.I have checked it with a volt meter no volts.Everything seems to work except this one light, fuses checked all working.The bulb holder has a green wire coming out the bottom any ideas where the problem is.
DENNIS DAY

Is there a heater light as standard? I did not think there is one. Is this perhaps something that has been added? If so, it will depend on how it was wired.

The only light with a green wire to it that I recollect is the seatbelt warning light - it is greed into one side and yellow out the other to the module where it earths. On the bulb holder you have is there an extra connector on it? Is there a loose yellow wire in the near vicinity (it will be either yellow/red or yellow/purple - I cannot remember)

However, if it is this bulb, then the green is live with ign on. Have you checked the inline fuse holder with white in and green out? It is on the inner wing under the main fuse box.
Hal Adams

Heater light?? No idea what you mean. Oh, do you mean the rear screen heater?
Mike Howlett

a photo,location and a bit more description might help!
Michael Beswick

On a ’78 the rear screen heater warning lamp is part of the switch.
Geoff King

Heater fan switch illumination? They were on 77 and later MGBs, powered from red/white and black with the night-time illumination. The green to that switch powers the heater fan, not the bulb. But then the bulb and its holder are internal to the switch, so maybe not.

More and clearer info neaded.
PaulH Solihull

The bulb that does not light is the one in the hot cold round switch in the centre console its on the left of the clock on a 78gt in front of 1st gear.All the other bulbs/switches/gauges lights work fine.
DENNIS DAY

Do you now mean the panel light that comes on with the sidelights that illuminates the heater control?

This should not have a green wire 'coming out the bottom" It should be red/white and will have 12V with lights on. If no voltage, then trace the red/white wire back to its connector that joins all the panel lights
Hal Adams

The bulb now works when the ignition is on.Turn ignition key off light is out is that correct.The bulb holder has a green wire to the centre and a yellow with a purple stripe wire to the earth part of the bulb/holder. The wiring looks like it has not been touched it all looks correct.
DENNIS DAY

Backlighting for the heater control. It should illuminate with the side lights whether the ignition is on or not, the same as the distribution knob on the other side of the clock.
Geoff King

Yellow/purple and green is the seat belt warning lamp.
Geoff King

Problem solved the heater and seat belt lights were in the wrong places changed them round now everything is working ok thanks for all your help.
DENNIS DAY

Strewth, I never knew MGBs got so sophisticated as to have illuminated heater controls. No such luxury on the two I have owned (1971 and 1969). When its dark I have to remember which knob does what and which way it turns, and I almost always get it wrong!
Mike Howlett

"I almost always get it wrong"

Me too, I have a 73 and a 75, and the rotational direction for heat changed between those two.
PaulH Solihull

This thread was discussed between 27/11/2012 and 29/11/2012

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