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MG MGB Technical - Slow indicators and dodgy horn

Hi,

My uncle has just bought a MGB, 1973, in pretty much perfect condition, near enough show condition infact.

Anyway, a problem has been occuring which is intermitant, it comes and goes. The indicators on both sides start working extremely slowly, literally the lights stay on for 5 to 10 seconds then off for the same amount of time. When this fault occurs the horn also goes. It still makes a noise if pressed but a very weak noise, as if only one of the horns is firing and even then, weakly.

Both faults occur at the same time and when one starts working properly again they both do. Could this just be caused by the cold weather?

Cheers, Phil
Phil

Phil; As I recall the ground circuit for the horn and front signal lights is through a bullet connector located behind the grill. Old double bullet connectors sometimes corrode and get brittle and internally split. Look for the connector with the black wires and check the condition of the connector it may crumble in you hant. If it's good make sure its clean and the bulled fits tightly. Use a die-electric grease on the connectors. It's a good idea to replace all the double connectors in the front the those in the trunk.
Clifton
Clifton Gordon

Thanks Clifton,

I'll pass the message along. However, I doubt that this is the problem. He's only owned the car for a month and it has been totally restored - new shell, the works. I used to own a GT myself and I had a quick look at the wiring just to check its general condition. It all looks superb, new wires - everything, so I doubt the connector will be in poor condition.

Has anyone else got any suggestions?
Phil

Phil; My suggestion wasn't very good because the horns get their ground through the horn button and are not grounded through the bullet connectors. I should have looked before answering. Sorry. I think I need to finish waking up before making any other suggestions. Clifton
Clifton Gordon

Definitely not the cold weather, it is a fault on that car. Both problems are probably caused by low voltage due to bad connections somewhere. If both problems come and go together they must be linked, and the only place the horns and indicators *are* linked is where the brown wire from the fusebox joins the brown wire from the ignition switch, and back from there down to the solenoid and from there to the battery or solenoid depending on whether the problem only happens with the engine stationary (but ignition on), only when the engine is running, or both. It could also be a faulty alternator going off charge intermittently. Any of these would also cause pretty-well everything else on the car to be affected as well, like lights (interior and exterior), wipers, heater fan etc.

With the engine switched you should have about 12.8v on these browns, a little less with the ignition on but the engine stopped, in excess of 14v when the engine is running over 1000 rpm, although this can drop to 13v or lower with lots of things switched on. You need to check the voltages both when the problem is evident and when it is not and compare.

With the best will in the world you cannot tell the condition of a connection by looking at it, manky-looking ones can be electrically sound and vice-versa. Connectors of all types can easily be a source of problems in a car 30 years old, and if they have recently been replaced then that itself can be a source of problems, with poor quality replacement parts or not assembled correctly.
Paul Hunt

Don't discount a intermittent problem in the alternator. This is one of those times when a voltmeter on the system would be very helpful. If possible, check the voltage in the system when the problem occures, anything less than 12.8 volts indicates a problem with the charging circuit.
Good luck - Dave
David DuBois

This thread was discussed on 24/01/2005

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