Re: [DML] Fan Fail Light Without Actual Fan Fail
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Re: [DML] Fan Fail Light Without Actual Fan Fail
- From: Martin Gutkowski <webmaster@xxxx>
- Date: Mon, 13 May 2002 09:52:20 +0100
Hi Jim
Do I take this to mean you have the OEM fan fail module? I have had the
opportunity to take mine apart and I thoroughly concurr with the
statement (if it's there, throw it away!).
Forgive me if I start talking too techy here... the fan fail module is a
simple hall effect sensor. It measures the current drawn by each fan and
if there's an imbalance between the two, the current generated by the
coil is enough to light the light. Wonderful, if it weren't so badly
made! I imagine there's a slight imbalance in your two fans - nothing to
loose any sleep over - but at 13.5v there's enough difference to turn
the light on.
At the moment mine has a simple 4-way daisy-chain of spade terminals so
that the fans and the fan-fail light all come on at the same time. This
is a very simple way of telling you that power has been fired to both fans.
I have designed but not yet built a fan sequencer which restores the
fan-fail light functionality. I discovered these superb high-side
switches which have an integrated "status" output which can be used for
the fan fail light directly. Mine treats each fan seperately and detects
a short or open circuit.
The circuit diagram is here (duplicate for each fan)
http://www.delorean.co.uk/electronics/fandelay2.jpg
to read an explanation, you'll have to join dmc_electrics and read the
archives :-)
Martin
#1458
jwit6@xxxx wrote:
I know I could probably just go with one of the fan fail fixes out there but
I'd like to understand a little more about what's actually happening.
Originally I had a fan fail indication when the spade connectors on the two
circuit breakers would heat up and sometimes trip the breaker. Those
connections are now fixed for good. No appreciable heat build up, resistance,
or current draw.
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