TAC20 1079 Fault

We have a unit that historically traps people intermittently. People get into elevator at an upper floor 3 or 4. (Its a 4 stop) As soon as the PI inside elevator coming down toggles to 2 the report is the elevator stops. IMS comes up with the fault and this always takes place with weight in the car.
We have been through all the connections, boards, selector, and found a bunch of stuff but not the problem. I have never adjusted a dover overspeed valve but could that be our issue? Now, to release the passengers we press the reset button on control board. Car doesn't run up it comes down on a leveling speed so I guess my question is..... Anyone have an overspeed valve partially set to slow car but not stop it? Open to a fresh idea!

It may try to recover up before shutting down on the 1079. You can test it by just closing the ball valve on a run down. It’s possible that it’s a bad contact on one of the 2 down slow relays so it stops as soon as it drops high speed trying to slowdown to stop at 2. I wouldn’t screw around much more before getting weight out and checking down high speed and setting the rupture to the upper end of the acceptable range. It’s way too common for someone to increase the down empty speed on an I2 valve not knowing how the down fast adjustment works. I remember having to let the inspector decide if he wanted 150 full, 125 empty or 180 full, 155 empty. Been a while, not sure if those numbers are right but that’s roughly how I remember the down adjuster working. I just recently had 3 cars trapping people with 1079s and found out a consultant wrote up the down speeds so the mechanic sped them up.

I'd be doing the same thing. Getting weights and a tach out and adjusting speeds on main valve and rupture valve. I had a car once for a year intermittently trapping folks early in the morning. But noone had details, just customer got them out. Car ran fine, I swapped alot of parts around with another car. Finally happens again and I talk to the folks trapped and they said it always happens when they're riding it down with the floor scrubber machine in it.... it was the main valve not being regulated going too fast, tripping rupture valve.

Just a heads up if you've never adjusted an i2 valve before. Only adjust the down speed if it's moving, on the buffers, or ball valve closed and man lowering open. Theirs more too it like half turn adjustments only but I'm not the guy to give that information cuz im just guessing off what ive been told. A guy who knows a lot about the dover valves is linden elevator. He's got a website and that's the # frome the site 1-208-754-4884

All good ideas. I will follow up on them and let you know were it takes me. Thanks,

have you caugt it in the act? have you check all the valve relay contacts? you may be getting a down demand, the relays engerzing but no down coil, and times out causing the 1079 fault