REFLECTOR: RG Problem

[Dave Black]

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