Low gear stopped working

I have a 1994 Haas VF-2 that won't shift into low gear. I replaced the MAC solenoid valve that controls the shifting...no go. The spindle just oscillates, then alarms out. The alarm is 118 spindle low gear fault. All circuit breakers are on. Any ideas??
Thanks,
Carl

Cheenist said:

I have a 1994 Haas VF-2 that won't shift into low gear. I replaced the MAC solenoid valve that controls the shifting...no go. The spindle just oscillates, then alarms out. The alarm is 118 spindle low gear fault. All circuit breakers are on. Any ideas??
Thanks,
Carl

Click to expand...

Check your incoming air pressure. It is shifted by an air cylinder. Minimum of 85 psi, but maybe a little higher would get it to shift!

Mike

Thanks...air pressure is good. I have owned this machine since new and have done all repairs and service work myself. I'm a fair shade tree mechanic but definitely lack electronic skills.
Carl

Dang, I was hoping!!!! The rest of the guys will chime in soon.

Mike

I would first determine where the problem is. I am assuming that it is not the solenoid because you already replaced it. The air is good as stated already. The next thing I would do is to manually activate the solenoid. As the spindle is moving back and forth for the gear change, I would take a thin object and press the button on the solenoid. If the machine pops into gear then there is a problem with the power going to the solenoid. If the machine does not go into gear and you are sure it is getting the air, then the shifter in your gearbox is damaged. Replace the gearbox.

I would definitely try to manually activate the soleonoids and/or check for power going to solenoids as suggested by Jason.

If that doesn't work, try disconnecting and reconnecting the air supply (Quick connects only) to the machine while the spindle jogs back and forth trying to select a gear. Sometimes the shaft for the shift select gets gummy and doesn't want to move easily. By disconnecting and reconnecting the air, the surge of air can cause it to release and allow the shift. Sometimes have to repeat several times. If that doesn't help either, check to see if the spindle is in either high or low gear at power on. If it is in either gear, zero all the axis individually then turn the spindle on to try and warm things up for a bit. Then try the air supply on/off again during a shift.

Unless there has been some kind of crash, I would bet that things are just dirty/gummy with the shift mechanism.

Good luck.

The gearbox on my SL30 was giving me trouble and it wound up being a burned out wye delta contactor. There is a parameter that turns off wye delta that will let you shift if that is indeed the problem.

I had a similar problem on my VF-2. It wound up being a faulty proximity switch that looks for the position of the High/Low shift arm. The light would energize on the prox, but it was not sending the signal to the control.

LISTEN

I have dealt with this. in 99% of cases, it is either the flow orifice on the mac valve or the limit switch on the bottom of the trans that only "indicates" the gear selection. You need to first verify if the trans actually shifts gears or not. This is pretty easy to verify by trying the spin the spindle by hand. high gear = easy, low gear = harder.

If the trans is not shifting, there are 2 copper lines going to the trans. Pull them both at the mac valves, find the small orifice "pills" between the mac valve and feed line, and try an MDI gear shift. If you get air from the mac, you found your problem. I got so tired of it, I drilled the orifice slightly over sized, problem solved for good. The orifice serves to soften the gear change a bit. Do NOT getting nutty on the drill. .001-.004 oversize will do it.

Mine does seem to clank into gear a bit more now but I doubt anyone else would even notice. The right way to do this should have been another pressure reg with full pilot pressure to the solenoid. faster and softer at the same time.

I have had the same problem on 2 out of 3 gearbox Haas's to get it back into high gear you can let it run in the highest rpm in low gear to warm up the gear box. I f that don't work you have to take off front cover and remove draw bar actuator and manually move gear shift this will put you back in high gear. At the end of the day always run the spindle in high gear before you shut down the machine as long as I do this the machine has been fine.