The Car Polisher vs The Ten Step Troubleshooting Process!

Gather 'round young'uns and let me tell you a tale.

A tale of mystery and intrigue.

A tale of the time the car polisher slowed down!

Gather 'round young'uns and let me tell you a tale.

A tale of mystery and intrigue.

A tale of the time the car polisher slowed down!

Long ago I worked at a car wash
where we had a troublesome car polisher.

Over the years we had suffered all manner
of breakdowns with the thing.

Long ago I worked at a car wash where we had a troublesome car polisher.

Over the years we had suffered all manner of breakdowns with the thing.

It got to the point that, once we had the dern thing runnin' again, I had the maintenance team record every valve setting, every cycle time, even the temperature in the reservoir, so we would know when things were off.

Wait, you didn't already have that..?

This was the old days. We had to start at some point!

Wait, you didn't already have that..?

This was the old days. We had to start at some point!

Anyway, that's how, months later, we were able to quickly detect that something was wrong.

No one's sure when it first started, but it must have been building for a while.

The car polisher was definitely slowing down...

No one's sure when it first started, but it must have been building for a while.

The car polisher was definitely slowing down...

It's true!

So one day, on a slow afternoon, I got the team
together and we got to work figuring this out.

They wore PPE back then?

Oh yes! Safety was very important!

They wore PPE back then?

Oh yes! Safety was very important!

First, we had to Define the Problem.

We knew that the machine was cycling slower than normal and after some closer observation we picked up on a few clues.

After the polisher has reached the back of the car, as it begins to travel forward again, it slows down for a moment. Then speeds back up to normal.

At the end of the cycle, the horizontal brush was slow to rise.

The fluid temperature in the reservior was noticably warmer than usual.

Was this a flow problem, a pressure problem, or a directional problem?

Flow Problem

Actuators move too fast, or too slowly.

Pressure Problem

When tackling the heaviest loads, actuators:

stall (in a kinetic state)
can't maintain position (in a static state)

Directional Problem

System normal in one direction only. Reverse function is compromised or non-existent.

Well... since the issue was due to the machine cycling slower than usual,
it would be pretty safe to say it must be a flow problem.

That's exactly right!

Well... since the issue was due to the machine cycling slower than usual, it would be pretty safe to say it must be a flow problem.

That's exactly right!

Next, we Consulted the Schematic.

We noticed that there were two solenoids that were
active only during the two stages that had noticable slowdowns.

Solenoids 25a and 31a.

We noticed that there were two solenoids that were
active only during the two stages that had noticable slowdowns.

Solenoids 25a and 31a.

With this info in hand we went and got the List of Suspect Components that can cause a flow problem.

Now if'n I remember correctly, that gave us a list of about fifty suspect components.

But because the problem was intermittent we could cross a few things off the list right away.

A bad pump is bad all the time!

This still left us with a fair number of suspect components though.
But we could easily Isolate Subcircuits, givin' us a clue as to where the problem lies.

See, there were these two ball valves on that machine.

One that isolated the brush cylinders...

and another that isolated the travel motors.

See, there were these two ball valves on that machine.

One that isolated the brush cylinders and another that isolated the travel motors.

When we took out the travel motors, there was no change. The problem remained.

But when we isolated the brush cylinders the problem went away!

A clue!

Yes!

But did it mean that the problem was in that subcircuit,
or just that removing the flow demand of a third of the
circuit was enough to mask the problem?

Yes!

But did it mean that the problem was in that subcircuit, or just that removing the flow demand of a third of the circuit was enough to mask the problem?

Next we had to Determine the Order of Checking.

We first started with the Physical Observations.

Look, listen, and feel. That sort of thing.

We first started with the Physical Observations.

Look, listen, and feel. That sort of thing.

That's how we got our next clue.
A loud hissing could be heard from cylinder 29 while it was retracting.

It was one of the brush cylinders.

That's how we got our next clue.
A loud hissing could be heard from cylinder 29 while it was retracting.

It was one of the brush cylinders.

That was around the time we decided to look at the evidence we'd collected.

Initially we knew that:

The polisher was slowing down, but only at certain times.
The horizontal brush was slow to rise.
The fluid temperature in the reservior was warmer than usual.

In addition we had learned that:

The polisher only slowed down during the stages when solenoids 25a and 31a were active.
The issue went away when the brush cylinders were isolated from the system.
One of the cylinders was making a hissing noise when it was retracted.

And the hissing cylinders retracting which just so happened to only occur during those stages when solenoids 25a and 31a were active.

With all this evidence in hand we were pretty confident the
problem had to be caused by that brush cylinder. Cylinder 29.

With all this evidence in hand we were pretty confident the problem had to be caused by that brush cylinder. Cylinder 29.

Now in those days we didn't have all these dern fangled fancy
cylinders you have now.
We're talkin' about a budget price, utility cylinder here.
Not worth the cost to repair it.

Now in those days we didn't have all these dern fangled fancy cylinders you have now.
We're talkin' about a budget price, utility cylinder here.
Not worth the cost to repair it.

Instead we Replaced it with a brand new one.

Having replaced the cylinder we ran the machine through its paces a
few times just to Verify everything was working nicely again.

Having replaced the cylinder we ran the machine through its paces a few times just to Verify everything was working nicely again.

And wouldn't ya know, it worked!

Finally, with the car polisher back to polishing cars,
it was time to do some Root Cause Analysis.

We took the cylinder apart on the bench and
discovered that the piston seal was starting to fail.
This was lettin' fluid bypass the piston when the rod
was trying to retract, which was slowin' the thing down.

Finally, with the car polisher back to polishing cars,
it was time to do some Root Cause Analysis.

We took the cylinder apart on the bench and discovered that the piston seal was starting to fail.
This was lettin' fluid bypass the piston when the rod was trying to retract, which was slowin' the thing down.