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Triumph TR6 - Music is fading

Hi guys,
I need the help of you who understand things electrical.
I have a radio/CD and small amp in my TR6 and when playing a CD as soon as the revs go over 3000 in any gear the music starts to fade in and out in a pulseing fashion and disapears completely at 3200 rpm.
Then comes back on when the revs dip below 3000.
I been advised it might be caused by too much voltage.
I've tested the alternator and the radio/CD at idle,
14 volts on each and at 3000rpm, 15 volts on each.
I'm certain the radio/CD is well grounded but will try a test today with a direct ground lead .
I have electronic ignition but have been advised that it probably isn't the source of the problem.
Any ideas?
Christopher Trace


I can't help with your problem. Sorry. But, could it be that the Brits designed the TR6 in such a way that music would fade at 3200RPM just so you could hear that sweet sound from your tailpipes? Sorry, couldn't resist but do wish you well in solving your problem. I have a AM-FM stereo cassette system in my dash that I bought just to fill the hole. I never did get around to making all the connections so it's just a filler plate.

Good Luck
'76 White TR6
Bob Evans

Hi Chris

15v at the device is a bit high? Your Rg should be cutting out earlier. Most modern audio devices aren't quite that fussy though.

Take the car to whatever parts store and have the charging system checked first. Battery and alternator. I would suggest a cab/RV type alternator if theres a problem. Bosch seems to be best from the local guys now. Most of the other new repop stuff will not handle high current drain at all.

Don't know how big your amp is? Whats the wire gage to the amp? For any of them 8 min. right from the battery is advisable. I mean a seperate wire fused right from battery. Same or higher to the perfect ground...:)

The charge/discharge rate of your coil seems to be the culprit. From what you describe. But see below! May be just added load?

This just popped into my head! Have you checked your fan belt for slip? High current and high rpm will cause them to slip? Had one looked good and float at high rpm? Tape was wonky before sometimes at speed? I found the problem on a dark rainy night. Lights/wipers/ radio on. Car kept trying to die at any higher speed. Stop and it charged low rpm.

Bob at 3200 in 5th Chris's Ford powered TR is more about aftershock soundwaves? Just kidding..:

Some idea's

(Still waiting for HO fuel injected)
Bill Brayford

electric fan so no slip, Amplifier is only 100watts
and wires are the way you say and 8mm.
Charge/discharge rate of coil? Elaborate please.
Alternator is GM 65 amp unit if I remember right.
Rg ? Do you mean voltage regulator inside the alternator?
Thanks bill
Christopher Trace

Hi Chris,
As a test do you have an old ballast resistor you can put in line with the hot side for the radio ?? I've got one that knocks 12 volts down to 10. You can do the same with resistors and make your own. I'm thinking 15 v at the radio might be too much.
Charlie Ballard

Hey Chris

Yes Regulator in alternator. That GM is famous for being poor by the way. But they will give you a new one under warranty almost always. Just have it tested on or off the car. Now have a 5 year guarantee. Run down a battery on a cold winter morning and they won't charge it without crapping out.

Picky picky. So what drives the alternator? Aha!! I will now refer to it as the alternator belt...:)

Yep so at half power with radio/cd/amp we draw maybe 10 amps. Electric Fan 10 amps. Can't remember your ign. system but say a crane maybe 5 amps. fuel pump probably 10 anyway not working hard. Some show as high as 25 but mostly for fuel injection.

Check in with Parts-Source or whoever you like. I like them because as a rule most of there guys took the testing equipment course. Someone doesn't get called from housewares to test your car? If you take it to them and that store has all the new stuff. Just turn on everything and load it up. Run up rpm to 3k and see what the 12 grand in gadjets tells you. Plus its free.

Should give you current draw load alt output voltage drop etc etc. And tell you if something goes haywire at that speed.

By the way I'm betting on a faulty regulator in the alernator sending some strange pulses down the wire under certain load and rpm conditions.

Since you just had the engine apart? Quick check of that alternator belt wouldn't hurt..:)


Bill Brayford

Thanks Bill,
The alternator was a rebiuld. Parts source?, is that a chain, haven't heard of them before.
Sounds like I'll start with the alternator.
Christopher Trace

Hey Chris

Look up whats close. Then call to find out services I can only go by the one here in Guelph. Others may differ?

The franchise is under Canada Tires corporate umbrella I think. But they don't carry mastercraft stuff any more. Stores go after the garage business and the high end hot rodder types.

Bill Brayford

I had the same problem. Turns out I'm deaf as a a post.

Hi guys, just to finish up this thread I took
Prof. Bills advice went to a PartSource store and found
the internal voltage reulator was shot and sending weird pulses down the line. Picked up a new Bosch
alternator with a 5 year waranty for $80.00 installed
it and the music returned. In addition to having music
over 3000rpm the ignition light has stopped flashing at me which it has been doing for three years.
Thanks to all who offered advice but mostly to Bill.
Christopher Trace

Congrats Chris:

Glad your problem worked out. Bosch alternator, huh? Sorry about the wisecrack. Good thing you've got Charlie & Bill around to steer you straight.

Bob Evans

This thread was discussed between 31/10/2004 and 07/11/2004

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