REFLECTOR: RG Problem

John Dibble aminetech at bluefrog.com
Tue Aug 3 07:51:38 CDT 2004


Thanks, Dave.  My engine monitor shows the voltage.  With the light off (5-12 amp
draw) it runs 14.1 v.  With the light on (12-20 amp draw) it is 13.9 v.  I should add
that my squat switch seems to be set a bit high.  On the ground (up on blocks) it
takes around 90 kias for the punp to go on and my speed is in that range when I have
the problem.  I can't find the switch and think I will have to remove the canard to
get to it.  I think adjusting the switch will solve the problem, but I wonder why the
light is affecting it.

John

Dave Black wrote:

> John,
>
> > Lately, when I hit the gear up switch, nothing happens.  If I turn off
> > the landing light, then the hydraulic pump comes on and the gear goes
> > up.  If the landing light is not on to begin with, then I need to
> > quickly switch it on and off to get the pump to come on.  Any ideas what
> > is going on?
>
> Nothing solid -- just brainstorming...
>
> Presumably there's no interconnection between the landing light and the gear
> pump. In which case, the only common point I can see is the main electrical
> supply. The landing light may be drawing so much current that the voltage to
> the gear pump drops below its operating level. Switching off the light raises
> the system voltage. If the light is off anyway, by this theory the pump should
> run OK. But maybe the voltage spike created by switching on and off the light
> is enough to give your pump that extra kick.
>
> Certainly this is not the way it should operate. I am assuming the pump
> originally operated correctly and only recently began this behavior.
>
> The first thing I would do is put a voltmeter across the hydraulic pump to see
> when it's getting voltage and when it's not. Also check what the voltage is. I
> would expect 12v or more when the gear is operating. If it does not run when
> it's supplied 12v, this would point to a marginal gear pump motor. Further
> bench testing should confirm this. A variable DC power supply could come in handy.
>
> If the hydraulic pump is receiving significantly less than 12v, I'd check
> voltages elsewhere in the electrical system. If voltages are low generally,
> that could point toward a defective alternator, regulator, or battery.
>
> If the hydraulic pump is not receiving voltage when it should, trace back
> through the wiring to find out where the circuit is broken. I'd be especially
> suspicious of any relays in that circuit.
>
> I suppose it's possible you may have an intermittent limit switch in your
> hydraulic system. I don't know how a voltage spike caused by cycling the
> landing light could reset a limit switch, but stranger things have happened.
>
> Sorry I can't immediately identify the source of your problem, but hope these
> tests can help lead you to a diagnosis.
>
> Dave Black
> Shortwing RG
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