Silverroadster

I have a 6 volt 1960 S90 Roadster and a 12 volt (converted) 1963 T6 coupe with a 912 engine.
In both cars, a very faint light appears in the ignition bulb, increasing in intensity as revs rise, but never so strong as the start-up ignition light from the same source.
I have had a 356 electrician go over the Roadster, changing the regulator and checking outputs-all fine, so he is flummoxed.
The brushes on the Roadster were recently renewed.
What can it be?

points

Loose belt.

Silverroadster

Silverroadster

Loose belt is unfortunately not the solution- I should have noted, the 356 expert also checked the belt tension and subsequently I had the coupe belt tightened to the same tension.

points

Of the 4 356 Ive owned the red light glow was either generator failure or loose belt. At high rams the loose belt slips and red light glows brighter. make sure belt is in good shape. It will be interesting to find out cause of your problem.

Albert911s

Maybe a ground issue to the guage.

zoomie50

A quote from Joe Leoni electrical Guru for 356s:Here's one of Joe Leoni's posts on this issue, from 2000:
[Subject: Re: red charging light
From: "Joseph A. Leoni" <356electrics@prodigy.net>
Date: Fri, 6 Oct 2000 09:02:49 -0600

The Generator Warning light is tied between the
battery (#15) and the Generator (D+). When there is a
difference in voltage, the light lights.
Since it is tied to the D+ at the regulator, it is seeing
the generator's voltage. On the T6C regulator there
is a bit of resistance in the wire loop, so just maybe
this problem might be less noticed in the "C" cars.

At higher rpm the Generator is probably putting
out more current. Then there is more drop in the
system to the battery. This drop or difference is
what causes the dim red light. What is interesting
is that the light is indicative of the charging current
and is occurring when the generator's voltage is higher
than the battery. Just opposite of the light at idle.

Where the drop develops is not important. It can be reduced
somewhat by cleaning the CO contacts in the regulator,
and tightening all the connections to the battery/terminal block.

Lastly, if your battery is more fully charged, there will be less
current flowing to charge the battery, hence less dim red light.

Have your regulator checked, and adjusted to 7.3 volts at the D+
terminal. This then allows for a slight drop to the battery, so will
probably not be much over 7.2 volts. The more current you draw
the brighter the @#$%& red light.

In the meantime, don't worry about it.

Hope this helps,
Joe

cscrogham

Before you get too deep into this, ck the spring tension on the brush holders. I found a set of smaller springs recently that did not push the brushes into the armature properly.

Kuro Neko

Good advice!
As the problem is applicable to many 6V 356, and as noted is of course is due simply to a voltage (not current) difference between the battery and regulator output.
At low rpm, you can even see it pulse in time with the commutator rotation.
Cleaning all contacts, brushes, terminals, connections, and stuff can fix - microscrub and a can of electric cleaner in hand.
Until it starts again...

's fix was red nail polish.

My fix was a 12V conversion...