Welcome to our Site for MG, Triumph and Austin-Healey Car Information.


MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB GT V8 Factory Originals Technical - The music is fading

Hi guys,
I have an Alpine CD player installed in my V8 converstion with a Kicker amp. When playing music on the CD player, as soon as I go over 3000 rpm in any gear the music fades, sort of pulses on and off and disapears and comes back on when the revs come down.
I think the unit might be picking up a signal from the
electronic dist.
Does anyone else have an opinion or know if there is a
filter that will stop this interuption.
Christopher Trace

Could the voltage be going too high and the CD/Amp cuts out. Faulty voltage regulator perhaps - Does the fuel guage go up a bit when you rev the car?
Stuart Robson

3000RPM's! That's when the music starts! ! ! :-)
Sorry. Couldn't resist.
John Renaud

I would start with a volt meter and see what's happening when you hit the higher rpm's. Second: What is the radio grounded to? Same grounds as the rest of the cars electrical system? It might be worth giving the radio its own ground to chassis. Sometimes a clean ground path can work wonders. Some spark plugs and wires can mess with stereos, but I doubt that's the case.

Voltage, then ground.

No fuel gage is steady.

I assume that you mean I should test voltage going into the radio/CD to see if it spikes at 3000rpm?
If it does then can I assume that the voltage regulator
inside the alternator is faulty?
Thanks guys.
Christopher Trace

just tested the alternator and the radio/CD for
voltage at idle and at 3000prm.
Both registered 14 volts at idle and 15volts at 3000rpm.
I think that is nomal. The radio/CD is grounded to the heater box which is bolted to the body, I'll try a
jump lead from the radio/cd to the body tomorow and let you know.
Christopher Trace

Try holding the revs at 3500 or so, with the problem affecting the CD, and disconnevcting power to the ignition. If the interference stops instantly the implication will be that it is the ignition causing it, if it only fades out as the revs drop then probably the alternator (which remains charging until the revs drop below about 600 rpm).
Paul Hunt

Hi guys,
just to finish off this thread, the problem was the
internal voltage regulator in the GM alternator.
It was sending werid signals up the line.
Replaced it with a new Bosch unit and all is working fine now.
Thanks for all the help.
Got it fixed on the last day of the season, we had snow
last night. It will be a long four months.
Christopher Trace

This thread was discussed between 26/10/2004 and 09/11/2004

MG MGB GT V8 Factory Originals Technical index

This thread is from the archives. Join the live MG MGB GT V8 Factory Originals Technical BBS now