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MG MGA - Radio interferance

I've recently noticed that when I apply brakes on my MGA, static comes through the radio. I don't think this was always the case and wonder if there is sparking or poor contact somewhere. Every thing seems to be working but the brake pressure actuation switch is an unknown quantity. I've read that these can be problematic but its a lot of work to remove it without good reason. Could one put a meter across the terminals and check the resistance?
J H Cole

JH,
When you apply the brakes are you hearing static the whole time the brakes are applied or is it only a click on the radio as the brake lightning circuit is initially energized?
I would think if it is only one click, then it might be the current jumping across the contacts at the brake pressure actuation switch.
When I had a 64 B, I put a condenser at the fuel pump. I could hear the points opening (or were they closing) and that created a click on the radio. One condenser cured the clicking. You might try that method at the brake switch.
My experience is old radios do not have good tuners and if the radio station is far away, then you hear quite a bit of the car electrics.

Ray
Ray Ammeter

Ray: The interference/static goes on as long as the brakes are on. This is what concerned me as the pressure switch may not be making a good contact. Is this a sign that the switch is on the way out and does one have to rebleed the brakes if a new switch is fitted?
John
J H Cole

John,
That is probably a sign that the switch is going bad, but it could be a loose wiring connection or a corroded lamp socket. I have read that you don't need to bleed after changing the switch but I don't know. If you can get to the switch and put a meter across the two terminals, it should read 12 volts with the brakes off and 0 volts with them on. I think changing the brake switch is one of the things that is harder in the UK because you have the steering column in the way.

Jeff
Jeff Schultz

Ah yes, the old spark-gap transmitter trick.
marconi

My 1959 copy of Practical Automotive engineering mentions interference from static being caused by both tyres and brakes. So it might not be the switch. I do vaguely remember static being a problem with some radios.

The suggested cure for the brakes is to use Black Lead Grate polish. It doesn't say where you put it and I don't think it is a recommended cure nowadays.

The suggested cure for the tyres is to coat the sidewalls with Black Lead (again)or inject colloidal graphite down the valve.
malcolm asquith

Malcolm
I tried pushing the brakes when the car was stationary and apart from the small 'click'when electrical contact was made by the pressure there was no radio static so perhaps it does come from the brake discs/pads. I might try some copper grease on the rear of the pads but if its moving disc generated I'm not sure what can be done. Did'nt they used to produce electricity by friction, Vandegraf or someone like that.The more I think about it the more likey it seems and I'm not sure why its not more of a problem generally.

John
J H Cole

John
Don't believe this brake switch thing, it was always the pads/shoes that gave the static until you stop. Does that make sense? Where abouts in Hampshire are you then?
Pete
Pete Tipping

This thread was discussed between 30/01/2005 and 03/02/2005

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