Ralf wrote:
When I move my flaps down at about 70% of the travel my pump comes on for approx 0.5 to 1 sec. The flaps then retract without the pump coming on. When I move them down again at 70 % travel the pump comes on again. (the pump is continuously on when it starts up – it does not come on and off in very short intervals)
When I pull the circuit breaker I get almost 3 complete flap cycles out of the accumulator.
I tried to bleed out the air from the system at the fittings of the flap cylinder, the accumulator and the bulk head where it goes under the rear seat. I do not get any air – just oil.
When I filled my hydraulic system the first time I did not have this problem – I got approx 1.5 flap cycles before the pump kicked in.
I changed two things in the mean time:
1. I increased the flap cylinder stroke by approx 5 mm (1/4 “) by adjusting the hard stop.
2. I removed and put back in all hydraulic lines that run from the front to the rear of the cabin on the floor (I found a significant cabin pressure leak in the tunnel for the hydraulic lines under the front seats that needed to the fixed)
The function of flaps and gear works fine. Is the described situation acceptable or do I have to worry about air in my system that needs to come out (and how to get it out if so)
Ralf,
In my opinion, the pump coming on for “0.5-1 second” is not normal for an IV-P hydraulic system with a functioning accumulator, which seems to be OK from your later description. I can’t imagine how air in the system could cause this cycling, but have seen strange things with hydraulic systems, so perhaps it’s possible?
It sounds to me like the pump relay is being triggered by something other than the pressure switch. Is there any chance you have a bare or pinched wire in the pressure switch wiring that’s being momentarily grounded/shorted during flap movement? I don’t mean to insult your intelligence or craftsmanship, especially after looking at the enclosed picture, but one of the purposes of the accumulator is to keep the pump from “cycling” like this, and according to your description above, it does so for other operations. Do you get any “blips” when cycling the gear?
My system engages the hydraulic pump with each flap extension, meaning I probably have less accumulator “capacity” than you do before the pressure drops below the switch trigger level. These switches have a range of open/close trigger values that affect this “capacity” as well, but the very short pump runs are, again, not normal.
If you don’t find a wiring problem, consider changing the pressure switch. That’s the easiest thing to do in the troubleshooting line. I have a spare in my tool kit that I could loan for this purpose if you’d return/replace it after your test. Contact me off-line if interested.
\
Bob