Allis Chalmers electric forklifts

I have lifted the drive wheels and tested. The drive works fine without load in both directions back and forth. There does not seem to be any hesitation with the drive wheels off the ground.

My first thoughts were the direction sensor or the drive potentiometer. After the wheels up test, I am not so sure about this.

Any comment?

 

When I reinstalled the brushes, I didn't take note of the direction of the longer leads in the T and where they were, so I obviously installed them backwards and my motor spun backwards.  After correcting, the motor now spins the proper direction and power steering works excellent.

 

To note:  The proper direction for the pump on this machine is clockwise rotation when looking at the shaft of the pump (where it connects to the motor).  The fluid inlet is on the bottom, pressure outlet is on the top of the pump.

 

The reason I was not getting power steering to work after I initially installed the new brushes, then changed them and tested, was because when I went and changed them, I did so by not removing the entire motor from underneath the rear axle.  I just pulled off the back end of the motor housing where the brushes are, and switched them there.

 

PROBLEM WAS.... when I did so, I must have pulled on the armature slightly and it pulled away from the pump a little, dislodging the armature key.  So when I retested the motor with the brushes changed, the motor wasn't turning the pump and it was at that point that I thought I was going nuts.  I finally had enough and took it all out again, only to find the key sitting in the bottom of the motor housing and me feeling rather stupid.

 

In short, if your power steering needs servicing, elevate the rear of this model forklift (ON BLOCKS, safety first) and remove the entire unit because if my experience with the armature KEY is standard factory, then this is not like anything I've ever seen.  Most keys are insterted in the side of a shaft, but not this one.  It is a little round extension, male on one side, female slot on the other side, keyed into the end of the armature shaft and mates with the pump.  My pump still has an Allis Chalmers stamp on it, so I believe my entire setup is still factory.

 

At any rate, reading NIKT above shed some help about these forklifts for me, which was useful.  Hopefully my crazy experience will help someone else by reading this.

 

All the best.

 

I see we have at least two problems to solve--one, the drive system, and, two, the power steer system.

 

Let's keep chugging along here while my A-C pals keep digging for a wiring diagram.

 

Drive System:  Would you please clarify one more time--If you manually close both the Forward contactor and the 1-A bypas contactor, does the drive motor run?  And does the motor run with the Reverse contactor and the 1-A  both closed?  If the motor doesn't run under these conditions, then there is an open in the drive power circuit.   

 

You can check motor continuity:  With all cables disconnected from the motor, there should be continuity from S1  to  S2 (letters stamped into field ring).  These are the series field coils.  Note: some field terminals were  marked F1 and F2, so keep an eye open for this.  The armature terminals should be marked A1 and A2.  Both the armature and field windings in the motor should have a low resistance, typical HUNDRETHS of an ohm.  Usually the the fields almost never fail, but a shorted field coil(s) wold tend to make a running motor want to run faster, but pull an abnormally high current and while causing much brush sparking.  If there is no armature continuity, you may have stuck or worn brushes.  Remove the cover bands at the brush-end of the motor and take a look.  If the brushes seem to be well down into, or flush with the brushboxes, they are definitely worn out.  Brushes and all motor parts are readily available from people like Warfield Electric Co, 815-469-4094 for reasonable prices.

 

Power steer problem:  This sounds like a hydraulic problem.  If the lift and tilt work OK, then the odds are the fluid level is OK.  Since the power steer motor seems to run OK, then you may have a hose or component problem.  Check the hose that feeds the inlet port of the power steer pump to make sure it is not collapsing from suction vacuum.  It may help to know how this system works:  This system is a full power assisted sytem with no mechanical link between the steering wheel and the small diameter steerable wheels located at rear of the forklift.  The power steer pump sends fluid to an Orbitrol valve controlled by the steering wheel.  There are four ports in the steer valve--the inlet port gets pressurized fluid from the pump, while two of the ports are connected to the power steer cylinder.  When you turn the steering wheel to the left or right, fluid is directed to one side or the other of the power steer cylinder to move its piston one way or the other to steer left or right.  The fourth port on the Orbitrol is the drain line back to the reservoir.   I would suggest pulling the drain line that goes from the Orbitrol drain port to the tank, and aim it into a deep bucket.  Run the power steer motor briefly to see if fluid is being pumped at all.    Assuming there is sufficient fluid in the tank,  if there is no flow, then the suction hose may be collapsed or a filter may be clogged.  Usually a suction side restriction will result in pump cavitation and cause a high pitched noise.   If you have good flow in the drain line, turn the steering wheel to see if the steer cylinder and linkage move.  If not, try to raise the steer wheels off the ground and repeat the test.  If the wheels then steer, you may have an abnormally steering low relief pressure.  The relief valve is typically built into the power steer pump.  You should set relief pressure with a gauge as you could blow the lines with excess pressure.  You should hear the power steer motor/pump unit speed up and slow down as you steer , and you should hear the unit run slower when you get to either end of the stroke of the power steer cylinder.   If you get thes audible clues, but the no steering, you may have a rare case of the piston breaking loose from the piston rod and just moving back and forth in the cylinder without doing any steering.

 

Try these hints and let me know how you make out.

 

NIKT