Werner,
Fair warning. The following is all wild speculation and hand waving. I
hope you get a response from someone with actual experience with the
problem.
It is possible your problem is not the fan, but the voltage regulator,
and the timing with the fan change is coincidence. However, it is also
possible that one of the fan leads is a ground that is connected to the fan
case and hence to frame ground on your car, and you now have reversed leads
so you've put in a near-short. You may have done this already, but couple
of simple tests will be helpful: 1) Disconnect the fan entirely and check to
see if the problem does indeed disappear (also do this with all the other
electrics on to check with a load on). 2) Reconnect the fan with the leads
in the original configuration, running in the intended direction, long
enough to see if the problem is absent. At least then you will know for
sure that the problem is due to the fan change.
If you have an ohmmeter, you can check resistance from each
disconnected lead to ground. If that seems OK (high resistance), it is
possible that the problem is aerodynamic. Fan blade designs are often not
going to work very well in reverse. Moreover, if it is trying to run in
reverse, with poor efficiency, with significant obstruction (the radiator)
too close to the suction side, I suppose it is possible that the blades get
into an aerodynamic stall and simply spin the air around with the blades
rather than passing it axially. When that happens, it is doing very little
work and would speed up while the amperage would fall. When the stall
suddenly breaks and air starts moving again, it would slow down and the
amperage would go up. Note that if it is a voltage induced speed change,
the amperage would track the speed. So there is another check.
Good luck,
Ron Kerans
-----Original Message-----
From: Werner Pels <wernerpels@earthlink.net>
To: Morgan List <>
Date: Sunday, April 07, 2002 6:47 PM
Subject: 1970 Plus 8 Radiator Fan
>With warmer weather on the way, I've been doing various things to help my
>car's perennial cooling problem. Since I installed it on the front of the
>radiator about 30 years ago, I've always wondered whether changing it to
the
>back side would make a difference. I finally did so and, of course,
reversed
>the fan motor leads.
>The fan now does a good job of pulling air through the radiator at idle,
but
>it behaves strangely when I accelerate. When I do, the fan speed (judging
by
>the noise) accelerates, too. When it goes fast enough that it sounds as
though
>it's going to disintegrate, it cuts back suddenly, then starts accelerating
>again and the cycle repeats. If I watch the ammeter, the needle moves way
up
>into the plus zone as the fan accelerates, then falls back slightly minus
when
>the fan speed drops off - then up again as the cycle repeats.
>At first I thought that the fan was being "driven" by wind coming through
the
>radiator, but that's not it. It does the same thing if I simply rev the
motor
>standing still.
>Does anyone have any suggestions?
>Werner Pels
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