Hi Peter,
This is quite normal. A DC motor if wound over by hand generates power
(remember the old bicycle dynamos?). You will be finding that as you reach
a certain speed the fan will be turning, winding the fan motor over and
generating a back voltage (dependant on speed but probably around 5-7v)
making the lamp glow dimly.
Don't worry, it's not harmful. I find my one comes on at around 50 mph.
It is possible to get around it by putting a diode in series with the fan
so that the back feed can't get to the lamp, but I haven't quite got around
to it on my car yet. The diode you would need should have a current rating
of around 10 amps to allow for the startup current on the fan motor
(normally around 8amps depending on the fan).
Hope this helps
Cheers
Bernard
'71 2500PI
'73 TR6PI
At 12:51 20/08/2001 -0600, Peter Zaborski wrote:
>Listers,
>
>A while ago I converted my TR6 from the mechanical fan to an electric one. I
>also installed an indicator light to illuminate whenever the fan is on. I
>used the wiring diagram in Dan Masters book as a guide. The light and fan
>are powered by a common terminal from the relay which is switched on by
>either a thermostatic switch or a manual switch. The fan is a pusher, so
>it's mounted on the front of the radiator. All works fine as far as cooling
>when required. However I've noticed one interesting phenomenon. The
>indicator light glows dimly when ever I get up to certain speed. Doesn't'
>matter which gear I'm in, as long as I'm going a certain speed, the light
>glows. The faster I go the brighter it glows. Not as bright as when the fan
>is actually turned on, but bright enough to be noticeable. My assumption is
>that at a certain speed, the fan turns from the force of the air moving past
>it and acts as a "generator" which in turn makes the light glow. Does this
>seem right? If not what else could it be? If it is my theory, is this normal
>behavior for pusher fans? Is it causing any harm?
>
>Thanks for any insights.
>
>Peter Zaborski CF58310UO
>
>
Regards
Bernard Robbins
NEC New Zealand Ltd
Network Solutions
P.O. Box 1936
Wellington
Ph (04) 381 6274
fax (04) 381 6284
email brobbins@wlg.nec.co.nz
http://www.nec.co.nz
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