LW4000 hitting car

[washnvac]

(different issue than mcallen)

Having an intermittent issue with one of my Lasers. On the first p/s pass, once it starts up the passenger side, it will stop just before the middle flag and turn to go across (like it thinks it is at the front). Prox tests on/off ok. Of course it never happens when I am there. But it has to be getting a two pulse in from the prox, right?

Can anybody send me in the general direction? Should I just replace the prox switch first? Any quick thoughts are appreciated.

Also, is that prox supposed to be shielded or unshielded?

 

[JGinther]

Seen the same issue before where the festoon cable would short and make a false signal when it was in just the right spot. I would try driving the machine up and down while having someone watching the input light for a flicker... Or keep shaking the festoon cable while watching the input. No front or rear photo eye faults I'm assuming?

 

[BBE]

I would start with the eyes in the side T bar. Those are responsible for measuring the front and rear of a vehicle. First check the gain on them, maybe you just need to turn it up a bit. Worst case scenario, replace them. The set of eyes on the exit side of T bar are the ones responsible for measuring the front of the vehicle. And the ones on entrance side measure the rear.

 

[whitescout]

As the machine travels up the PS, it is looking for the middle limit input, and then it is looking for an input from the front Tbar eyes. If these conditions are met, then it will have the bridge stop, and have the arch rotate.

If the machine does not receive an input from the middle limit, then the machine will continue until it receives an input from the front limit, stop and rotate.

I would agree with the other posters, that you are receiving a false input, but you will need to figure out which one. It could be from a bad wire in the festoon cable, or it could be wiring, ( wago terminal corrosion) in the J3 box. It could also be the input devices themselves(front prox switch, front tbar eyes, amplifier or relay for the tbar eyes, or the input module, or even the output module)

I would start with the front limit prox switch and cable, and I would check by moving the bridge to the failed location and shake the festoon cable like Jginther said, to see if I could get the front limit input to come on. If the front limit comes on, this is what is making the controller turn early, as it thinks it is at the front of the bay.

I would also do the same check for the middle limit switch. If the middle limit comes on, then the controller is looking for input 21, so it knows when the front tbar eyes are in front of the car. Input #21 is shared for front tbat eyes, and rear tbar eyes. If the rear eyes are able to "see" each other after the controller receives the middle limit input, the controller will use the rear eye input 21 as the front eyes, and will think it is at the front of the car.

The front and rear tbar eyes share the same wire for the input, but receive power from different outputs. Depending on the year of your machine, you will either have 2 amplifiers in the J3 box, or you wil have relays and one amplifier.

 

[washnvac]

A little more info I discovered today. It is happening on small cars with little or no trunk. It did on a vw bug, and two small hatchbacks today.