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MG MGB Technical - seat belt warning light

Could someone tell me what the seat belt warning light should do on a 1980 MGB GT? Is it supposed to come on for a set length of time (or until the seat belt is fastened)?

The light on my car never comes on even though the bulb is working. I think that the fault lies in a small unit labelled "Pektron" - I believe that this may be the "time delay unit" but I don't know what this is supposed to do. It is being fed with 12V but gives no output. Before I attempt to investigate the fault any further, I'd like to be clear on what this unit (and hence the warning light) is supposed to do.

Any help and advice would be greatly appreciated.
Gwyn Coleman

I don't know why your question has not been answered by someone from this board, so I'll tell you what I know (ain't much).

I believe the "Pektron" you refer to provides output to the "seatbelt warning lamp", while simultaneously screeching its warning. The lamp is illuminated when the Pektron (assuming this is the correct name) provides a ground (earth). So, you will detect 12VDC at the lamp, but until the Pektron does its part, the lamp will not light.

Had I known ANYONE would crave the awful noise this unit makes, I would not have discarded the one I ripped out of my 77B about 3 weeks ago.
Fred Doyen

The seat-belt warning light and buzzer should come on for a period of time if the car is started without the seat-belt fastened.

Personally I never fasten my belt until I have started the engine, so I'm thankful I don't have one, and would have disconnected it by now if I had!

I rewired a UK 1980 and that one didn't work either (before or after), but the owner wasn't bothered so I didn't investigate further.

Paul Hunt 2

Gwyn,

On my 1973 MGB I replaced the seat belts when I redid the interior of my car. The new belts did not have the warning hook up, so the seat belt warning system was no longer an issue. However, it bothered me having the seat belt warning light on the dash console sitting there doing nothing. Therefore, I bought and hooked up a small timer relay which I mounted under the dash, that I can set from zero to infinite, Now, when I turn my key to start the car, the seat belt warning light comes on for about 20 seconds and then goes out. As for the seat warning buzzer, since they did not have warning systems on 1973 cars for leaving your headlights on, I rewired the door switch so if I leave my headlights on and open the car door, what had been the headlight warning switch now beeps at me.

Just a suggestion.

Robert
Robert Browning


Thanks for all the replies so far. I have now opened up the Pektron unit on my car but it does not contain a buzzer - just some resistors, capacitors, a few transistors and a couple of diodes.

I'm guessing that it should either cause the warning light to flash or to come on for a set length of time. Presumably, a previous owner has replaced the buzzer unit with this thing. Does this sound familiar to anyone?

I've ordered replacement components and will get my soldering iron out when they've arrived!

Thanks again for your help,

Gwyn
D G Coleman

Gwyn, you're going to replace the internal components, or you've ordered a new Pektron unit? You've found a schematic for the internals, or you're going to "dead reckon" your way through it? It sounds like something I would have done in my early days, before I accumulated great wealth (oil wells in the back yard, millions of head of cattle...so on).
Fred Doyen

If your car is like my 1974 MGB GT, the light only comes on if someone or something is in one of the seats. If you get in the car and buckle your seat belt and then start the car, the light wouldn't come on. There was a seat load sensing switch in the seat which was also part of the circuit. If I place a large pile of books or a brief case in te passenger seat, then I had to buckle that belt to get the light and alarm to shut off.
William McCord

"I have now opened up the Pektron unit on my car but it does not contain a buzzer"

An interesting point. The earlier American system contained a separate buzzer and control unit. The later unit is described as 'Time delay unit' in both markets, but North American cars had an extra wire going into the unit compared to UK cars, from what is described as the 'buzzer door switch' (for when the door was opened with the keys in the ignition), but no separate buzzer. Either the American unit *did* contain a buzzer, or the door switch retained its old description but was just another path to light the lamp.

North America had three different types of warning system, in 71/72, 73/74, and 75 on, the UK only one from 78 on.
Paul Hunt 2


Thanks for all the replies. I've opened up the Pektron box and have replaced all of the capacitors and transistors. (The other components appear to be working correctly.)

The unit now causes the seat-belt warning light to flash until the seat belt is fastened. I am reasonably sure that the unit is now functioning as it was intended to but, from what you have all said, it sounds like this Pektron unit wasn't originally part of the car.

Thanks again - I'd still like to hear from anyone who has experience of a similar unit!

Gwyn
D G Coleman

This thread was discussed between 24/09/2006 and 05/10/2006

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