|
Bryan,
Adding a Continuous duty relay (master relay) is a poor
fix to many a problem. I have heard this so many times it kills me.
IMHO, the correct wiring fix is to modify the Lancair
wiring diagram. In my airplane, control power comes from downstream the 50
Amp relay as opposed to any other main bus. Wiring it this way as opposed
to the manual diagrams prevents the relays from being energized with power off
the pump relay (continuous use on non continuous relays lasts 10 minutes - I
know).
Additionally, troubleshooting this circuit is
relatively simple.
If wired correctly, switch up or down should power
associated relay through the appropriate pressure cut out switch.
Things happen..... The switches occasionally go
bad, however, one ship in my shop has 20 year old switches that are so far
working great fresh out of the 20 year old boxes. Also, pressure issues
can develop. Specifically, it takes a while to purge the air from the
system. I'd recommend several open dump valve bursts of 20-30 seconds (in
one direction) as an aid to purge air. Air in the system makes the
pressure switches a little persnickety. Bottom line, pressure gauges
although not required do expedite the trouble shooting process.
Another could be gotcha; If you've got power to
your yellow "pump in use" light, make sure the two relay feeds are
separated with a diode. If not, you'll get a push me pull you activity
betwixt the relays/and / or pump.
When the pressure circuit is met, no power should be on
the relays.
Larry Henney
L360
850 hrs (about a third of that time spent contemplating
the hyd system)
My lancair 360 was wired professionally. When we tried to do the gear
retraction tests.....nothing. We checked all the wires and made sure all were
getting power where they should. Checked the breakers, switch etc.
We overran the relay and the motor ran so we figured it was a bad
relay......went to Napa and bought 2 new relays today. Installed them. Same
thing....nothing. Then we remembered that the relays were mounted to a
fiberglass bulkhead and the case needed to be grounded so we attached a ground
from the relay mounting base to ground bar.
Tried the gear.....now it worked...BUT it instantly fried the ground
wire on the relay small terimal......tried to measure the ohms of the relays and
no resistance....how could it be that I have 4 dead relays all brand new?
So today I installed a Master Relay. The ones that are all metal
case. Now the gear works and no wires are getting fried........but Im not happy
with this result as it makes no sense why the normal relays for this job aren't
working....anybody have any ideas?
Bryan
|