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MG TD TF 1500 - Radio Installation

I have just tried to install a modern radio into my car and have the following problem.
With the engine not running the radio works fine.
When I start the engine the sound become intermittent like a CD Skipping.
This occurs when tuned to a radio station, playing a CD or using the AUX input from my phone.
I disconnected the aerial. No difference.
It is mounted in the glovebox. I tried removing it and holding it in my hand with the same wiring. No change.
I placed a Meter on the input voltage - steady at 12.6 v.
The moment the engine stops there is no problem.

The car is a MGTD with pertronix electronic points and pertronix coil. New Spark plug leads. Negative earth.

Any thoughts on a solution?
A J Clapham

Check your terminal connections at the speaker A J. Also I think you will want to add a capacitor to the ignition system. I think David S. would be helpful here. Until he chimes in, I'd also take the power straight from the battery and see what happens.
I'm not positive but I think resistor type spark plugs are in order along with suppression type spark plug wires.
LaVerne

Could be a bad ground/hot that is being aggravated by the car movement from the engine vibration.
Mike
Mike TD/TA

Take the fan belt off and see if the noise goes away. If it does, the noise is coming from the dynamo. If the noise is still there it is coming from the ignition. Cheers - Dave
David DuBois

Like David D said ...try that.

Most likley unshielded ignition is the problem. Another way to test for that would be to hook the radio up to a 12vdc source other than the car (spare battery/not connected to your car).
If the noise is still there when you do that it is caused by unshielded ignition. Resistor spark plugs and suppression plug wires should get rid of most of it.
Any good hi-end stereo install place (not best-buy) should have noise suppression filter you can put in-line on the 12vdc supply also.
Alternate source might be a marinia ...common problem installing radio's in boats.
If all that still fails you can try "shielding" the glove box with a copper mesh to reduce RF.
David Sheward

AJ,
I did exactly the same thing,,, it had me baffeled,,, it turned out to be an interference from the fuel pump!!!! Each time the magnet in the pumpe energized, it would send a signal to the radio and that interupted the sound,, you can prove this by reving up the engine so the pump has to deliver more fuel,,, the inrterupting of the sound will also increase in speed..

SPW
STEVE WINCZE

Thanks for all the suggestions. They make a lot of sense.
Will check them out and advise on results.

Alan
A J Clapham

The problem is the radio has intermittent sound when the engine is running.
I have tried the following;
Removed the Fan belt- no change
Disconnected the fuel pump- no change
Disconnected the earth to check it. Radio still ran. it was earthing through the aerial. - No change Reconnected the earth.
Connected to and external power supply from my other car- Problem gone
I am chasing up some suppressors for the ignition. However I am not getting a hum or buzz just a loss of sound. The Graphics on the front panel still display & move.

Thanks for the input

Alan
A J Clapham

Resistor spark plugs and suppression plug wires should get rid of most of it.
Do that first...definiyly RF noise from unshielded ignition.
Our TV cameras used to go nuts when I did drag racing...we would wrap the in tinfoil and that helped a lot. Problem with that then becomes "heat". A copper mesh around the unit for shielding will allow the unit to still get air but block RF ...if the plugs and wires don't do it.
David Sheward

Problem Solved

Installed resistor spark plugs. No more problem
Also installed new Suppression plug leads.

Thanks for the helpd
A J Clapham

This thread was discussed between 20/03/2012 and 01/04/2012

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