Laserwash 4000 Arch turning too early.

Hello,

I have a Laserwash 4000 and here is the issue that I am having with it.

All other wash cycle is okay but when it goes on to the Spot Free Rinse cycle the Arch turns too early.

What I mean by "too early" is that the arch would not go all the way back to the back bumper of the car, rather is stop at the driver side door of the vehicle.

I believe the machine thinks the arch position is at the back bumper position and it starts climbing up the vehicle and eventually stalling because the impact switch would go off.

I read on the other posting (https://www.carwashforum.com/threads/lw-turning-too-early-when-coming-up.15294/#post-116767 ) that the front x30 prox sensor may be the issue but as I am a beginner with this so I wasn't sure which one was the "front x30 prox sensor" was.

Could anyone explain those for me? thank you.

This is usually a complex problem. The lw4000 goes around the vehicle on spot free by crossing the front of the vehicle until it sees the x24 left limit proximity sensor come on (treadleplate design) or until the VT card counts the proper number of pulses on the x30 width pulse prox and tells the arch to rotate from home position to the 90 degree position (Virtual Treadle design). Then it switches from y40 exit end of the bay tbar eye power to y41 entrance end of the tbar eye power. This should cause the return signal x21 tbar eye sensor to go out. Next it begins moving down the driver's side of the vehicle toward the entrance end of the bay. It's looking for two things in order to turn across the back of the vehicle. With a normal length vehicle, it should see the x26 mid limit prox light up and then at the rear the x21 tbar eye sensor should light up. This normally tells the machine it's time to cross the vehicle. On short vehicles the x21 tbar eye will light up first. In order not to tie the spring hose into a knot the bridge will continue back until it sees the x26 mid limit prox light come on. Then it will continue for a very short preset time and cross.

Your issue is probably going to be multifaceted. First, I would check the x26 mid limit prox located on the passenger side of bridge. It's the lower one of the two towards the exit end of the bay. Has it rubbed or chipped. Is anything other than the mid limit flag hanging down in its line of sight. Don't forget about the festoon cable and track. It doesn't have to be metal. Second, check the tbar eyes. Are the cracked or chipped. Test to make certain the machine is seeing both sets correctly. Their relays can be found in J3 on the exit side of the bridge. Finally, check your red festoon cable. Wires 7, 8, and 9 carry the signals for y40, y41, and x21. If the wires touch then you can inadvertently send a signal to the JO that the tbar sees the rear of the vehicle.

I will admit that it's unusual that it's waiting to the last cycle of the wash. It usually happens more towards the front.

Thank you. I will give that a try.

Call PDQ