Paul :
The spark should be the regulator relay contacts opening (which is
normal), and it's normal for tapping on the box to have an effect on the
ammeter.
I'd say the most likely explanation is a bad connection somewhere, but
it could also be a bad control box or generator. Some simple tests :
With the engine running at fast idle, check the voltage between the
generator housing and the 'E' terminal on the control box, then between
the housing and the ground post on the battery, and then between the
generator output (the large terminal) and the hot battery post.
Anything more than a few tenths of a volt indicates a bad connection.
(If you are using a digital meter, successive readings will probably
vary. Look for the highest reading of several.)
With the engine off, disconnect the lead from the F terminal at the
control box and measure the resistance from the F to D terminals.
Anything over 1 ohm indicates a bad box. Remove the cover, and put a
piece of paper between the regulator contacts, then recheck the
resistance between the F and D terminals. It should now be somewhere
between 50 and 100 ohms. Too high or too low indicates a bad control
box.
Measure the resistance from the disconnected F wire to ground. It
should be between 6 and 8 ohms. Less indicates a short in the wires or
the generator field winding, more indicates an open/bad connection in
the wires or the field winding.
It's also possible the relay contacts are dirty. Try cleaning them with
some fine emory cloth, followed by a rag dampened with carb cleaner or
petrol.
The book procedure for testing the generator is to (with the engine off)
disconnect the F and D leads from the control box, and connect them
together with a voltmeter to ground. Start the engine and observe the
voltmeter while slowly increasing engine speed. The voltage should rise
"rapidly and without fluctuation". An engine speed of 750 rpm should be
enough to give 15 volts generator output. Do not rev any higher than
that, or let the voltage exceed 20 volts (which could damage a good
generator).
BTW, if you don't have a voltmeter/ohmmeter, Harbor Freight sells a
cheap digital unit that is frequently on sale for $10. I like to keep
one in the trunk.
Hope this helps
Randall
59 TR3A daily driver
Paul Brandsema wrote:
>
> List,
>
> The ammeter on my TR4 is fluctuating like crazy. Seems to get worse as the
> engine revolutions increase. Noticed after I connected the ground for the
> voltage regulator. My first guess what intermitent ground. Cleaned off the
> contact surface on the stud but no change. Removed the cover from the
> regulator and noticed a spark that seemed to coincide with the movement of the
> ammeter needle. When I tapped on the regulator, it seem to have an effect,
> moving the needle faster. Any ideas as why this is happeing would be
> helpful.
>
> Paul Brandsema
> 61 TR4 CT133
>
> Get free email and a permanent address at http://www.netaddress.com/?N=1
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